> So by violating the first rule of clean code — which is one of its central tenants — we are able to drop from 35 cycles per shape to 24 cycles per shape

Look, most modern software is spending 99.9% of the time waiting for user input, and 0.1% of the time actually calculating something. If you're writing a AAA video game, or high performance calculation software then sure, go crazy, get those improvements.

But most of us aren't doing that. Most developers are doing work where the biggest problem is adding the next umpteenth features that Product has planned (but hasn't told us about yet). Clean code optimizes for improving time-to-market for those features, and not for the CPU doing less work.

- Slow DB queries

- Lack of concurrency/parallelism

- Lack of caching/memoization for some expensive thing that could be cached

- Excessive serialization/deserialization (things like ORMs that create massive in memory objects)

- GC tuning/not enough memory

- Programmer doing something dumb, like using an array when they should be using a set (and then doing a huge number of membership checks)

With that being said, I have worked on the odd performance optimization where we had to get quite low level. For example, when working on vehicle routing problems, they’re super computationally heavy, need to be optimized like crazy and the hot spots can indeed involve pretty low level optimizations. But it’s been rare in the work I’ve done.

This article is probably meaningful for people who work on databases, games, OSes, etc., but for most devs/apps these tips will yield zero noticeable performance improvements. Just write code in a way you find clean/maintainable/readable, and when you have perf issues, profile them and ship the appropriate fix.

I think the core problem here is that he assumes that everything is inside a tight loop, because in a game engine that's rendering 60+ times a second (and probably running physics etc at a higher rate than that) that's almost always true.

Also the fact that his example of what "everyone" supposedly calls "clean code" looks like some contrived textbook example from 20 years ago strains his credibility.

Edit: come to think of it, the only person I know of who actually uses the phrase "clean code" as if it's some kind of concrete thing with actual rules is Uncle Bob. Is Casey assuming the entire commercial software industry === Uncle Bob? It's like he talked to one enterprise java dev like 10 years ago and based his opinion of the entire industry on them.

He does have a narrow view, but it does not make his claims invalid.

I liked that his POC terminal made in anger made the Windows Terminal faster. But even in that context it was clear that by making some tradeoffs - which the Windows Terminal team can not make (99.99% of users do not run into the issue, but Windows has to support everything) - it could be even a lot faster.

So we live in a world where we cater for the many 1% use cases, which do not overlap, but slows down everyone.

Many gamedevs do their own tools, because they are fed up how slow iteration is. The same thing is happening at bigger companies, at some point productivity start to matter and off the shelf solutions start to fail.

This is perhaps the third time I've posted this on HN, but what you describe is the circle of life for widely-used software projects. Large tech companies are not immune to it, resulting in frequent component rewrites, deprecations and almost-drop-in replacements that shuffle complexity up or down the stack.

Step 1: Developer is fed up by how slow/bloated current incumbent is, so they write a fast, lean and mean project that solves their problems

Step 2: The project becomes popular on its merits, rakes in stars on Github as people discover how awesome it is

Step 3: Users start discovering limitations for their use cases, issues and pull requests pour in

Step 4: Thousands of PRs later, the project is usable by most people and has "won". It is now the incumbent, but no longer is as fast as it once was, but it also ships functionality catering to many niche needs

Step 5: Go to step 1

Like, feel free to fork away if you like. The core repository needs to be simple and stay true to its goals, and when it updates everyone downstream can update if they want to do that to themselves. But for what it is and does, maybe the project as it is is good enough.

I start feeling almost physically sick when I see the potential for bloat to creep into the software I write. This makes working with scaled software development with others particularly hard, however.

But i also think that the product, library or framework owner should really box in its project and reject wild growth of features and prevent generalisation of the usage.

It was literally a weekend POC, and Casey Muratori even went beyond the POC part and fixed some emoji/foreign language bugs that were present in the Terminal.

Also, his intent was not to replace the Terminal. His intent was to demonstrate that it was possible to do the optimization in the way he suggested. Originally a Microsoft PM dismissed his suggestions and claimed it would be a "doctoral thesis project" or something.

All this "yeah it's a narrow view" is just moving the goalposts more and more. Not only he has to do a "doctoral thesis project" in a few days, he also has to completely replace a tool that's already written, bells and all? Where does it stop?

Engineering tradeoffs are real. But hiding behind them every time when it can be pointed out that they don't actually apply - and when demonstrated with concrete evidence - is another thing altogether.

If that's his complaint, then "clean code" isn't the problem. The problem is capitalism and/or human nature.

Once something performs acceptably well, ie good enough to sell it, performance isn't going to get any better. Flashy stuff and features get you money, going from 400ms to 100ms gets you...nothing.

According to Amazon [0] that'd be a 3% gain in sales (assuming the inverse holds true as getting slower, anyway).

[0] https://www.gigaspaces.com/blog/amazon-found-every-100ms-of-...

> The problem is capitalism and/or human nature.

Fundamentally, yes.

I would tend to disagree on this, specially when claims come from the gamedev world. Games are presented as finished pieces (even when they aren't), and not just a release milestone. Ideally, a game is a one-off effort where you write a piece of code and if you're lucky, you won't have to touch it again. So, doing one-off optimizations instead of focusing on milestones and long-term maintainability of the code is not only a possibility, but actively encouraged. That's why until rather recently (20 or so years), assembly optimization for critical execution paths, if not for most of the product.

Most of the rest of the software doesn't work like that. You often implement something that will be maintained, modified, extended and reiterated on for several years, not by you, but by several other teams with totally different experience and backgrounds. Or decades. Doing some fancy trick to skip a cleaner, extensible, maintainable design because you shaved off a couple of cycles on it is literally burning your employer's money and potentially causing huge issues in terms of maintainability, as many programs don't actually rely on a happy path like games do.

The main reason modern systems are slow isn't (just) because programmers are lazy - Its because most software - unlike games - have compatibility and maintainability requirements, and more often than not, a huge legacy support. And also, in these systems, most of development time is actually spent maintaining and extending existing code, not writing new one.

The author's assertion is fundamentally wrong, because software engineering is quite more than performance - even when it matters. Flashback to the beginning of the 90's, and "every game" used bresenham's algorithm to skip usage of the (slow or non-existent) div instruction. In some cases, a couple of bit wise shifts would also eliminate mul operations. These implementations were in some cases 2-4x faster than the classical counterparts, on a 12-40Mhz machine. Two cpu generations later, the Pentium comes out, and both mul and div take 1 clock cycle. The fancy pants implementation is now 3-5x slower at the same speed. Except now the cpu clock is 4x faster and shoveling around registers may actually impede parallel execution of code. All of this in a 5-year window. I envy the relatively stable instruction set of the last decade, where everything is sort-of predictable and assertions of speed can be made on code with a relatively high degree of confidence, but the reality is, silicon is cheap, and for most applications, performance is gained not by throwing away what makes some huge applications barely maintainable, but by deploying hardware. New, fancy, faster, cheaper and more economical hardware. Choosing a single metric (performance) and an instance in time to bitch about something is actually a disservice to the community at large.

Where are you getting this information? Agner[0] lists DIV as taking 17 cycles at best (8-bit operand already in a register) on the P5, and MUL as taking 11 cycles. Even Tiger Lake takes 6 cycles for DIV.

There are ways [1] to beat that, but I don't think you can get it down to a single cycle.

[0]: https://www.agner.org/optimize/instruction_tables.pdf p.162

[1]: https://lemire.me/blog/2019/02/08/faster-remainders-when-the...

Ideally a game pulls in over a billion dollars per year, every year for over a decade. Think World of Warcraft or Fortnite, not Flappy Bird.

If there's something wrong with that advice, I can't imagine what it is...

It absolutely is, on toy problems like the one described in the article.

It very frequently is not when embedded in much larger domains as part of large projects maintained over years by teams.

The claim that "Clean Code" scales better or allows for more maintainable software hasn't been proven by anyone, and everyone with enough experience has worked with several counter examples.

The problem of code maintainability is not solved by this coding philosophy.

I'm totally onboard with prioritizing readability over performance for most code, but the style in the book has a lot more tradeoffs than it discloses, and you often don't really appreciate that until you are trying to debug if/how A transitively calls Z in a 10 million line codebase.

It's really hard to have a constructive conversation about this though since it's so subjective, any example is too trivial, and any real system is too large.

If you can't point to an actual example, I don't think you have a solid case.

However, the bigger your task gets the more value there is to polymorphism and in general the smaller the percent of total time goes to the polymorphism overhead.

And note that his attack is only on polymorphism, not the other aspects of clean code. I strongly suspect the compiler optimizes away much of the clean stuff I do but I have never checked. I also find profiling easier on cleaner code, it makes it very obvious where the time sink must be and thus what warrants expending effort to improve. Profiling almost always shows the vast majority of time going into the unavoidable (say, disk reads) and a small number of other routines. Spend your optimization effort on the spots that need it because 99+% of your code doesn't run often enough for it to matter.

One of the nice things about some of the clean code concepts he uses is that (as he shows) you can tactically step back from them in key, performance critical areas and reap these wins.

If you stay too low level you get lots of tangled spaghetti code with major performance problems and no obvious way forward besides "make it better."

Using procedures/functions is not exactly "low level". Using switch is not low level. Lookup tables are something you have to do in high level code all the time.

Sure he could have used much better variable naming (CTable?) and probably documentation, but code-wise there's nothing that screams low level there.

I would consider most of his replacements lower level than typical the clean code practices he critiques (especially the ones like iterators that he mentions but avoids in order to steel man the clean code side a little bit), not the lowest level possible. They take into account how the machine actually works and avoid additional indirection which is why they perform better.

Take Listing 27, getAreaUnion for example:

  f32 const CTable[Shape_Count] = {1.0f, 1.0f, 0.5f, Pi32};
  f32 GetAreaUnion(shape_union Shape)
  {
      f32 Result = CTable[Shape.Type]*Shape.Width*Shape.Height;
      return Result;
  }

  {-# LANGUAGE OverloadedRecordDot #-}
  
  data Shape
    = Square    { width :: Float, height :: Float }
    | Rectangle { width :: Float, height :: Float }
    | Triangle  { width :: Float, height :: Float }
    | Circle    { width :: Float, height :: Float }
    
  cTable :: Shape -> Float
  cTable shape = case shape of -- The "lookup table" or "array"
    Square    {} -> 1
    Rectangle {} -> 1
    Triangle  {} -> 0.5
    Circle    {} -> pi
  
  getAreaUnion :: Shape -> Float
  getAreaUnion shape = cTable(shape) * shape.width * shape.height

The stuff proposed in the post is not rocket science, it is a very straightforward implementation of tagged unions. Instead of fetching a vtable and jumping to a value there, he proposes to branch on the tag. This is essentially dynamic dispatch on a known set of types.

Additionally, he shows that this can result in speedups greater than a factor of 1. Any program that wants low latency or high throughput can profit from this observation.

This way of programming is by no means the one to rule them all. It has different advantages and drawbacks; none of which have anything to do with the percieved intelligence of the programmer or later consumers, for that matter.

An objective disadvantage of this style is, that the program can't interface with code, that hasn't been written yet, as a caller. Another disadvantage is that the size of the tagged union is defined by its largest "subclass".

In the end, what he has shown is that speed is often a compromise made unnecessarily. This doesn't really have to do with clean code anymore, as I can see how a compiler could implement what he is angry about with virtual functions in every situation where his style is applicable.

Casey has had a similar thing about the windows-terminal and somewhere in his videos a different, yet arguably worse, problem comes to mind: a lot of libraries do not care about performance enough. If you write a program and care, you may run into the problem that the library you use is your bottleneck. If this library is hard to replace (imagine needing a rocket-scientist), then you are done for. In that specific case it was DirectWrite and some other Windows-API that were slow. So if, for one reason or another, the windows team was required to use both, they'd have a hard limit on how fast they could go, just due to that. There is no "being smart" or "requiring a genious" involved in the forced/strongly recommended library here.

https://caseymuratori.com/blog_0015

It will start getting really annoying when you try to add shape ‘hexagon’ and need to figure out all the places where a shape can potentially be used, just so you can update the switch statements.

The author of the video discovered that C++ compiler is dumb when it comes to optimizing virtual method calls (that instead of bare virtual method calls he had to help the compiler to guess the right conditions where these virtual calls could be replaced with guessed static calls). Essentially, all that his video is saying is: "virtual calls bad if-else good". Which is like what every C++ game-dev thinks after few years on the job. Which is amusing in how short-sighted it is, and sometimes even more amusing to discover the "solutions" created by such C++ game-devs that are aimed at replacing C++ objects, but do it in a way that's even worse than C++ original design (who would've thought that to be possible!?)

Conversely, in a codebase organized by objects it's not clean to add an extra method to the base class and each subclass. You have to write an external function and switch over every known subclass inside it, which is also very ugly and will also break when you add more subclasses.

The two designs are actually the duals of each other. Someone compared it to rows vs columns and it's a great comparison.

In OO, the methods are columns and each new row is a new subclass implementing them.

In FP, the types are the columns and each new row is a function that switches over the possible types.

https://journal.stuffwithstuff.com/2010/10/01/solving-the-ex...

He also discusses it in his book Crafting Interpreters.

If your cases are defined externally, and you need to be forwards compatible, omitting a default is wrong.

The Swift language specifically added `@unknown default` for switching over enums.

But we can just re-up the problem by adding 100 different shapes instead of the one. Now you have switch statements with 104 cases each spread through your codebase.

This is the "expression problem": https://en.m.wikipedia.org/wiki/Expression_problem

ITs still possible to get a bottleneck in assembler.

Whatever language is used, executable code still needs to be profiled using tools as described here.

https://en.wikipedia.org/wiki/Profiling_(computer_programmin...

Casey's definition of simple actually reminds me of the cliché by Rich Hickley. It's simple, but it's not necessarily easy.

It's uncharitable to take Casey as making absolute blanket statements like that, but still, it would not be unreasonable for him to single out Uncle Bob in particular.

The Amazon rankings for Bob Martin's "Clean Code":

Best Sellers Rank: #5,338 in Books (See Top 100 in Books)

#1 in Software Design & Engineering

#2 in Software Testing

#4 in Software Development (Books)

I work in game development, largely with optimisation. I mostly work with GPU optimisation, which is a whole different beast. On the CPU, most of the time issues are either trying to do too much stuff in a hot loop (rendering stuff that could have been culled, putting physics on objects that don't need it,...) or doing something in a slightly inefficient way in a hot loop. Because everything in the game is indeed a loop consisting of a series of hot loops.

People in this comment section call his example contrived, but it's very similar to one of the biggest performance improvements I've seen in practice.

Still, each triangle's position, shape, and other properties can change each frame, as does that of the camera. So you cannot avoid doing some amount of work for each of the visible triangles and their vertices each frame.

Since you need to update the screen at a consistent frequency (typically 30 or 60 times a second) and the list of triangles that actually need to be rendered each frame is in the millions... Well, that's a lot of work which cannot be avoided.

Believe it or not, callbacks are not like interrupts, there is a loop somewhere that checks the status of something and then runs the callback. All computer software today involve things that run in loops, you just don't see it. Web browsers do it! Of course they do.

Moreover, he didn't contrive his example, he said that he in fact used a textbook example used by the advocates for polymorphism and such.

EDIT: To expand on this, why is modern software slow? The reason is because people, thinking their code isn't a bottle neck or performance doesn't matter but adherence to the right abstractions is, they write slow code and call backs thinking everything just happens immediately, with layers of abstractions, and those little innocent steps add up when every piece of code written today is written with that same neglect. The call backs runs slowly, queues fill, promises hang, and so-on and on we go.

So sure, may be your code doesn't seem like it needs to run at 60fps. But when everything I do on a computer is written like it will be run every 10 seconds, it definitely will be noticeable. That's because I don't just run your program or look at your website, I look at 10 of them or even more. If I average all of those per time, then may be your code should in fact be able to run at 1Hz or so or I will start to notice.

People of course were right not to teach new devs not to over-optimize immediately, but the culture has swung so far in the other direction, especially since you all seem to love complexity so much, you've managed to yes make computers that can calculate pi faster than a super computer from the 70s crawl when it renders and handles an editable textbox. There has to be a move back in the other direction, you guys need to give a shit about performance, at least a little.

    while (command != 'quit') {
       command = readline()
       handle(command)
    }

Game developers have the luxury of starting from near-scratch every once in a while. That exactly what his lauded handmade series is all about. I'm guessing that things wouldn't be so clear-cut if he was given a 10 year old codebase to iterate on.

"Normal" developers see game developers as gods walking amongst us and place far more value on their opinions than they should. The truth is that game developers and "normal" developers face equally as challenging problems, just different problems. As a trivial example, an experienced web developer could probably run circles around Casey in terms of elegantly accounting for browser quirks (conversely, the web developer would probably be stumped about data oriented design). Either could learn the other's discipline, but each would have decades head-start on the other.

The idolization of gamedevs is extremely frustrating, especially when it comes to appeals to their authority.

I agree that not everything is like a game, but it makes me legitimately sad when it seems like nobody cares about performance (aside from a few domains).

I find what Casey says in his videos to be true. And I though about that stuff before I even watched his videos, which are excellent.

However, I started not to care. I don't want to start fights inside the company, especially fighting alone against many OOP cultists. There's not my money at stake, so if companies as a whole decide for OOP, clean code, SOLID, design patterns, abstractions on top of abstractions, making the code bases giant pile of junks while degrading performance, I am not going to go against the crowd.

Code that I write for myself is quite different than code I write for my employers.

I just hope that the industry as a whole will wake up from the whole OOP nightmare.

I agree with that 100%. OOP is a giant mess, no matter where your stance on code clarity or performance stands. It's objectively worse in both regards.

This is simply not true, and has in all likelihood worked on such problems given his work at RAD whose software has been used in +20 years at this point.

> The problems of software performance come from decades of poorly/quickly executed evolutionary change resulting in bad systems design.

This may be true of some code bases, but it's demonstrably false for new software that's created today. Lots of new software gets built and it's slow.

Every story needs a Hero; it's inspiring when you're trapped in the CRUD gulag (until you see the TC/WLB).

Regardless of scenario I will never willingly do a O(n^2) sort when writing new code. Just in case those 10 items suddenly turn to 10000 one day.

If you are shipping a binary to your users that will never be able to get updates, your cautiousness would be justified. There are other situations where it will needlessly limits options.

There are situations where I have knowingly written O(n^2) or worse, and put a # xxx dragons marker by it. Quick to write, leave my options open, keep my momentum on the problem I care about.

I will grep for xxx issues at some later time. I may end up throwing out the code before that happens. If I hit big-o issues before then, I can refactor.

I once had a system where the important problems turned out to be a series of IO bottle-necks - nothing to do with computation - but that was obscured because good sense had been burnt at the altar of compute efficiency.

Even languages that are notorious for having tiny libraries, like C and JS, have built-in sorts.

The point is that the developers may think O(n^2) is fine because their toy use cases had n=10...100, but then actual users will try to use the software for n=10k, or n=100k, and then either waste their lives working with suddenly slow software, or look for alternatives.

I walked into a case like this the other day. I wanted to do a little semi-collaborative project planning. I found a nice tool, played with it for a moment, figured it has the functionality I need and it's fast enough. Then decided to do the actual plan. Once the number of entries in the system went from 10-20 to 30-40, I started to feel things get a little laggy. 50-60, more laggy. At this point I was committed, so I suffered the tool for couple of months, as its UI kept breaking when handling 100 entries. If I knew this would happen at the start, I'd look for something else. But instead, I walked into a hidden O(n^2) somewhere, that makes me hate the product with a passion now.

Generally, Casey seems to preach holistic thinking, finding the right mental model and just write the most straightforward code (which is harder than it looks; people get distracted in the gigantic state space of solutions all the time). However this requires 1. a small team of 2. good engineers. Folks argue that this isn't always feasible, which is true, but the point of these presentations is to spread the coding patterns & knowledge to train the next gen of engineers to be more aware of these issues and work toward said smaller team & better engineers direction, knowing that we might never reach it. Most modern patterns (and org structures) don't incentivize these 2 qualities.

That doesn't seem quite right. as 100 * (100^2) <<<<< 10000^2

Basically, performance doesn't compose well under current paradigms, and you can see Casey's methods as starting from the assumption of wanting to preserve performance (the cycles count is just an example, although it might not appeal to some crowds), and working backward toward a paradigm.

There was a good quote that programming should be more like physics than math.

Part of the compiler was O(N^2) in `let` block nesting depth. That is

  let x = foo(), y = y, z = 2y
    ...
  end

Until suddenly, `N` was in the thousands in some critical generated code spit out by some modeling software, so that handling the scoping introduced by `let` suddenly dominated the compilation time...

As a former .net developer that was often pushed into "clean code", my big takeaway from the video was that actually, not using "clean code" techniques, such as polymorphism made the code so much more readable and easier to grok that the optimisation that followed was completely natural.

It's the same thing with TDD zealots. Or any other fad driven development paradigm, which our industry is filled with.

Now, your argument seems to be: in the real world, there's so much waste, that virtual function calls pale in comparison.

This does not debunk his main point, which seems to me at least the following: all things being equal, writing code with virtual functions that do a tiny amount of work and "hiding implementation details" makes performance worse, sometimes by an order of magnitude.

Now, there maybe situations where you _have_ to use virtual functions, because you are writing a library for other people to use, and you can't dictate ahead of time how they will use it.

This again does not invalidate the point. You need to be _aware_ of the performance implications of this, and mitigate it. He said the following in the comment section on the article:

> Try to make it so that you do very rare virtual function calls, behind which you do a _large_ amount of work, rather than the "clean" code way of using lots of little function calls.

but all things are not equal. You can spend a lot of time improving performance of you function calls and get virtually nothing out of it. Because if you optimize something that takes 0.01% of overall execution time, 'order of magnitude' performance gain is still negligible.

Also articles like this usually fail to mention code maintenance cost. For example by reducing usage of virtual calls you can make your code unmaintainable/expandable and suddenly every new change will cost you 2x more in development time.

That's why in the real world most of the time you choose clean code and you use optimized nonclean code only on places where you need it. If you look at any lets say web framework internals, you will find a lot of non-clean code, which makes framework faster. But an interface will be done in clean fashion and most of user of the framework will enjoy clean code without need to care about unclean internals.

> Also articles like this usually fail to mention code maintenance cost. For example by reducing usage of virtual calls you can make your code unmaintainable/expandable and suddenly every new change will cost you 2x more in development time.

This never actually happens in real life. I've never seen a codebase that is written with "clean code" principles in mind that is also maintainable and easy to develop on top of.

Along with the heuristic that hardware and electricity are cheap, developers are expensive. That's probably why managers in my experience almost never ask developers to optimize slow code - they believe it would be cheaper to use more hardware if this fixes the problem (in some areas like HFT or GamDev more hardware is not the answer so optimization do happen). In rare cases I've seen optimization being done initiative always come from IC (who knew that the code could work fast / use less resources).

So nowadays writing code I assume that it never will be optimized later and try to do less dump stuff from the beginning.

Experienced devs - such as yourself - generally know how to write reasonably fast code that is also clean (or easy to extend) first time. In my opinion we should be more explicit about this in the heuristics.

We got slow software because we were ok to get slow software. If being fast is not in requirements it means it doesn't matter (for whoever is responsible for defining priorities). Places where performance matters it is never sacrificed.

I am not okay with slow software, and being forced to use it is frankly insulting. Teams (to pick a punching bag) hogging my system resources doesn't impact its adoption since I'm forced to use it. Teams could be 10x slower and I'd probably still be forced to use it. But it wouldn't be because speed doesn't matter.

If your program isn't slow then you don't need to bother making it any faster. Even Michael Abrash, who specializes in code optimization, once explicitly wrote in his graphics programming black book that "The objective (not always attained) in creating high-performance software is to make the software able to carry out its appointed tasks so rapidly that it responds instantaneously, as far as the user is concerned. In other words, high-performance code should ideally run so fast that any further improvement in the code would be pointless [..] Notice that the above definition most emphatically does not say anything about making the software as fast as possible".[0]

[0] https://www.jagregory.com/abrash-black-book/#understanding-h...

No it wont say something like that but if you profile Python itself and see that a lot of time is spent in Python you can get a hint that rewriting it in another language that doesn't have Python's overhead might help.

What problems do they prevent?

If you're able to make a program into a sort of puzzle concealing its state inside a twisty maze of tiny virtual functions so it's impossible to see plainly how anything is done, then you become indispensable as the only one who's internalized how the thing works.

And then you insist it's all for easier comprehension… for those sufficiently intelligent to comprehend it.

There are no hotspots. Computing has become lukewarm by default, and just like the globe, it's slowly heating up.

No, though s/any/many/ would make this true.

But you can only judge that for the very limited set of hardware you personally have access to. You might have many users -- or potential users -- with slower CPUs.

(ignoring projects made for fun of course)

When you hit Amdahl's law, it's because you (or someone else) has made decisions about the high level design/patterns to use in a system. To remove such bottlenecks, you may have to scrap the entire project and start over.

For the inner loops, it's perfectly fine to leave most of the optimization for later. But for overall design, it needs to be right from the start.

Time and time again, I see devs stuck in some paradigm (often front-end devs or low volumen RESTful microservices) that makes it almost impossible to handle non-trival data volumes or traffic, causing new products to fail.

I do agree that overall design needs to fit performance requirements but for the most part that has nothing to do with "clean code" patterns.

As an example, I recently worked on a large system that was optimized to do a big data transformation in an efficient way. It turns out that data is transformed back to the original format later downstream. So much for the optimization...

All that is to say, often it is the case that "simple > fast"

Clean code at the time had a lot going forward it, and it was an improvement over a lot of JavaEE code that was written in absolutely procedural ways with less care for the developer reading the classes, functions, or individual statements compared to punching out near assembly-like code and moving on.

Of course it will.

If your backend service is already suboptimal, and running at 10x worse performance, optimizing that will give you, well, a 10x performance boost.

Imagine replacing poor in-memory reimplementation of database queries that most graphql servers do with actual opttimised database queries. And a better code on top.

Boom. You're operating close to the speed of light.

but you are actually talking about optimizing system design, and not reducing virtual functions calls :).

And that the point of this thread: you need to optimize parts that slow you the most.

So no, in most cases optimizing virtual calls won't bring you from 1s to 30ms

On slower languages with slower runtimes, something that is 10x slower than normal code will have much more overhead than in the examples demonstrated by Casey. It won't be about "30ms vs 25ms" as some people are saying. In the past I remember seeing differences between 400ms and 20ms between JBuilder and .to_json in a critical endpoint in a Rails app, to give one example. Sure, one is "cleaner", but in the end it's a 20x overhead that has no place this case.

Also, the myth that "processors spend time waiting for IO" that is spread across this thread is BS. In reality, that's only true for single-user programs. If the app is part of a distributed system, the CPU time can be used to serve more users. This allows you to significantly delay more complex scalability efforts, which is also precious developer (or DevOps) time.

Not to mention that applying "Clean Code" in the first place also takes precious time, which could be used for features or anything making money, even optimizing the DB. Instead, this time is used to mess up the code in ways that have zero proven efficacy, and some developers instead think are terrible.

If you're working with databases, performance often boils down to minimizing the number of times you have to access the database (over a multi-service stack, not just a single web service).

With a non-pessimal design, not only you are able to pay less money on servers in the long term, you're also able to delay complex scaling strategies. Scaling also costs money.

Not to mention that building something with this kind of overhead also means that a lot developer time was spent in the first place, which is still expensive in our industry.

>Virtually every distributed service built today is able to take advantage of this

most of built today services can take much more advantage in using better system design practices.

There is this popular wisdom that security must be designed for from the start, and cannot be just added after the fact. Performance is like that too, except worse, because you actually can add security after the fact - worst-case, you treat the entire system as untrustworthy and wrap a layer of security around it. You can't do that with performance - there is no way to sandbox your app so it goes faster. You can only profile things then rip out the slow parts and replace them with fast ones - how easy that is depends on the architecture and approach you adopt early in the project.

I seldom wish I could post images on here, but I really would love to share a photo of the surprise coffee mug my work sent me, with a screen cap of a completely obliterated Y axis on a performance monitoring graph. Granted I don’t get to spend all my time hunting optimizations, but some teams/orgs/companies do very much value performance very explicitly.

Edit: and I’m definitely not a game dev. Though I’ve been itching to borrow some game dev techniques that are quite applicable for my domain (particularly ECS, entity component systems, which I suspect have far broader applicability than their adoption outside of game dev).

In my experience so far, it's typically the case that the 20 second DB query will annoy people for months or years - it won't get solved until enough people raise enough of a stink that someone finally prioritizes it. A large customer suddenly starting to make vague hints about bad performance is sometimes (but not always) helpful.

Some may say that "annoying, but not enough to make a stink about it" means it's fine to not optimize it. But I found that people can suffer a lot, and it doesn't mean it's harmless. People will adjust their workflows to minimize the frustration. When some of your "victims" are in-house users, the "not important enough" performance issue may be silently but continuously losing company money.

Among the many things I’ve learned as a self taught dev: you can be the person who raises enough of a stink if you care a lot. It’s not a thing you want to invoke frequently, but it’s a thing you very probably have power to invoke where it matters most. If you can make a good business case (or any case for user success that impairs your org), you have very good odds of being able to pursue it in any but the most toxic situations. If you can link $thing-you-want-to-pursue to other probably shinier biz/org goals, you’re 99% of the way there.

In a number of cases you actually can. Casey demonstrated it in his Refterm lectures, it's caching. You still call the slow thing, but at least you don't call it as often because you have that layer of caching to partially insulate you from its poor performance. Good luck if you have to deal with cache invalidation, though.

I'll concede on saying that performance and security are alike - you can add some of either after the fact, but you're better off thinking about both from the start.

> Good luck if you have to deal with cache invalidation, though.

Ain't it the truth. Adding a cache is easy. Understanding the implications of doing it is harder.

His final code is definitely simpler than the alternative, which would probably involve several files in another environment.

Sure, he does reach for a benchmark, but that's merely to demonstrate the end result.

Where our opinion seems to diverge is where I accept that as being fine, for the sake of being clean/legible/understandable.

You can of course only optimize what you are looking to optimize. I am not surprised (honestly) that some engineers do not realize they are in fact primed for the kind of things they will find based on what they are looking by the mere choice of where they want to look.

Honestly, for most software, a well performant "monolith" is probably enough.

We had one service that had a single-thread bottleneck that none of the developers could configure out - the solution was to spin up 30x more virtual machines to run instances of this app to meet average production demand.

There's a tipping point where you have so much hardware there's big savings with optimization. Things like Postgres and the Linux kernel have a lot of optimization put into them and there's an insane amount of hardware out running that code.

That said, slow software sucks.

Maintainability and cleanliness is the best virtue code can have. If you have extremely clearly written code that has performance issues I can swoop in with analysis tools figure out where the pain point is and refactor it out. Sometimes this is a real headache[1] sometimes not - what I can guarantee is that if the code is "dirty" it's going to be a headache and it'll take more time.

I'd personally take issue with this article over the polymorphism claim though - polymorphism is a tool but it isn't the be-all and end-all tool. A lot of your data can live as structs/blobs in memory with tight internal type definition but without any OO principals. Personally I am a huge fan of functional programming (but not pure functional programming) so objects that I use are relatively few and far between and exist to fulfill a very specific purpose.

I've had two occasions in working when I needed to break out an asm block - the compiler was being a thick headed dummy and this code needed to receive incoming signals without exception or delay - but once that critical section was passed? Back to high level programming and statements favoring expressiveness over raw bare metal performance.

If you want an interesting experience talk to your closest non-technical manager type - be that a product team manager or the company owner - and ask them if they'd prefer if you focus on reducing how long your product takes to execute by 20% over the next five years or if they'd prefer you to lower the growth of the developer labor budget by 20% for the next five years by focusing on maintainability over performance. With the exception of extremely niche cases maintainability is always the golden standard.

1. For instance, I've dealt with OOM issues that have required transforming all logic on a query result to be lazily evaluated on a data stream after main execution finishes - like the logic goes up and down the stack and only then begins processing results. In this particular case the problem was rather easy to deal with because we essentially swapped out the actual value passing on each layer for a lazy result set being passed around - because the code was clean. Sometimes you'll definitely need to massively re-engineer things though.

I feel like there's a misunderstanding here. Casey is clearly not against writing non-capitalized clean code at all. His code in the end is "cleaner" than what he criticizes IMO. What he is criticizing here is capitalized (and possibly trademarked) "Clean Code", the book and philosophy spearheaded by Uncle Bob.

Definitely get the single-threaded house in order before attempting to speed up by running in parallel.

Don't forget virtual machines and interpreters.

What I've seen is slow queries but a bigger problem is actually too many queries. It's easy to do especially when using an ORM.

It mostly happens on change when you want to add something to an existing query the changer just add their new query and slop it into a loop, boom performance is gone.

Over the years they've grown and one bin showed up where jobs would sit around for weeks--for that case n went from rarely having a screenful of lines to a few thousand--oops, now more than 2/3 of the time was spent in those searches. (And I have a sneaking suspicion that a good portion of the remaining time comes from using field names to retrieve values. The profiler doesn't separate that out, though, because it's not my code.)

- shit UX "ideas" that trigger 10 new API calls to show dialogs and popups.

- Logging libs under pressure

- overemphasis on testability

If shape Area is computed often enough that you care about inlining the calculation, why not compute & store it every time the height / width change. That’d be easy enough in an architecture based on information hiding, and might illustrate a legitimate engineering trade-off between those architectural choices.

Indeed. That's the point. Why let someone with an axe to grind define the problem in a way they can solve with their axe? The author is using optimization as the frame for rejecting a particular way of working, I'm pointing out that the definition is set up to make the solution work. I don't concede the terms of the debate before it even begins.

That's really not even close to true. Loading random websites frequently costs multiple seconds worth of local processing time, and indeed, that's often because of the exact kind of overabstraction that this article criticizes (e.g. people use React and then design React component hierarchies that seem "conceptually clean" instead of ones that perform a rendering strategy that makes sense.)

You attempted to present an argument that's a textbook example of an hyperbolic fallacy.

There are worlds of difference between "this code does not sit in a hot path" and "let's spend multiple seconds of local processing time".

This blend of specious reasoning is the reason why the first rule of software optimization is "don't". Proponents of mindlessly going about the 1% edge cases fail to understand that the whole world is comprised of the 99% of cases where shaving off that millisecond buys you absolutely nothing, with a tradeoff of producing unmaintainable code.

The truth of the matter is that in 99% of the cases there is absolutely no good reason to run after these relatively large performance improvements if in the end the user notices absolutely nothing. Moreso if you're writing async code that stays far away from any sort of hot path.

For example, in the case of web development, if you build a medium-sized website with React (i.e. pretty normal behavior nowadays), then if you make default decisions that don't consider performance at all, your website will end up noticeably slow, because you will:

1. Write code that re-renders components all the time during loading and UI interactions,

2. Which depend on tons of third-party dependencies that perform poorly,

3. So you end up spending a ton of time in re-renders while the site loads and while someone is using it.

Dealing with this isn't literally the same performance work that Casey put in his article, because it's at a slightly higher level of abstraction, but it requires the same mindset. It requires writing most of your code (and taking on dependencies) with performance in mind, not just 1% of it. You can't avoid it without your notion of "clean code" including some amount of mechanical sympathy, rather than just being about abstract extensibility and generalization concerns.

This is a mistake that I see far too many government and utility sites making.

If you're really interested in the impact of performance issues on everyday life, you need to provide concrete examples instead of putting up unverifiable strawmen.

The truth of the matter is that 99% of real world applications run just fine, and it doesn't pay off to invest in shaving milliseconds here or there. Would it be desirable to have a magic wand to improve some edge cases? Yeah, why not? Is it worth to pay people to spend time with a stopwatch at hand to shave off these milliseconds? Not really. It's all about tradeoffs, and there is no real world payoff in wasting developers' time to shave off that millisecond here or there.

There's so much hardware out there that can run native applications just fine, that can play back HD video, that can run complex 3D real time video games, but crawl like molasses when loading your average webpage. Facebook and YouTube are terrible offenders, but so are your average blogs. Many banking websites are terrible (yet they don't have to be; my local credit union has a zippy website that looks attractive to boot, has modern design elements, etc.).

Maybe the hardware you're running is eye-wateringly fast, or maybe it's just barely fast enough and you don't need the cycles for anything else. But we're not talking milliseconds. We're talking order(s) of magnitude. I can't bring myself to believe you don't see at least some of it, if you just open your eyes and look around.

"Unverifiable!", he wrote from within a web browser.

Let's not even get into low end phones in developing countries or bargain basement android tablets, let's stick with something straightforward - an ordinary PC.

I took a quick look online, sorting by cheapest first I found something with an AMD 3015e in. Based on cpubenchmark.net that gets a benchmark of 2691. Taking a look at the big list of CPUs I see that's equivalent to a powerful desktop CPU from 2008, or a decent laptop from 2012. (The Apple M2 in the current Macbook Air gets a score of 15369, just for comparison.)

So, if you're writing PC software or making a fancy web app and you want everyone to have a good experience with it then you should see how it runs on a terrible new laptop, or a 12 year old good laptop, or a 15 year old powerful desktop.

(And yeah we all have SSDs now which is much better than in the old days, and JS is generally single thread, and single threaded CPU performance has not improved so much - but I think my point still stands.)

Not to mention that web apps redrawing everything whenever they feel like it can almost give motion sickness, lead to clicks on the wrong things etc.

Yeah, but users' time is worthless.

Another app that I'm not sure if it's React or not is New Reddit. It is significantly slower on my computer and on a lot of people's computer and sometimes you have to refresh the page because it consumes too much memory.

I can come up with other local examples, from Germany. Vatenfall's website seems to "traditional" page navigation, but the content is loaded via a framework. Due to having to reinitialize everything, text takes up to 5 seconds to appear when using the back button or when navigating for page to page. Similar things happen in the German Agentür fur Arbeit.

You're taking deep quaffs of the Kool-Aid and so are most of the people commenting on this story. General software responsiveness and reliability (i.e., usefulness) has been in decline for decades. This is an objective fact.

Writing objective reality off as mere "milliseconds", "edge-cases", or only relevant for "toy problems" exemplifies the arrogance and severe incompetence of most programmers. People are seriously trying to talk down to Casey Muratori when in all likelihood they haven't accomplished even 1% as much as him as programmers.

I get it—no one wants to leave fantasy-land as long as the easy money is flowing. But sooner or later the glittering carriage turns back into a pumpkin.

It's certainly a huge problem for real world applications

My point being, if most of the program is slowed down by a slew of wasted CPU cycles (costly abstractions, slow interpreted language…), there's a good chance what should have been obvious bottlenecks get drowned in a see of underperformance. They're harder to spot, and fixing them doesn't change much.

So before you even get to actual optimisation, your program should be fast enough that actual optimisations have a real impact. And yes, actual optimisation should be done quite rarely. But first, we need to make sure our programs aren't as slow as molasses. See https://www.youtube.com/watch?v=pgoetgxecw8

I feel you're missing the whole point.

It's immaterial whether anyone can get to optimizations that compound multiplicatively. The whole point is that halving something that costs nothing earns you nothing. That's the whole point. Go ahead and shave off that millisecond. Will anyone actually notice whether you add or remove that penalty? Odds are, not at all.

Monocypher's speed was actually an important component in its success in the embedded market, even though I didn't explicitly target it initially (I was lucky my portability driven decisions made it a good fit there).

There definitely are niches where there are quite a few performance optimization opportunities that users do care about.

In your example making something a user is actively waiting for go from 3 seconds to less than one is a great optimization target. What is not a great optimization target is making something the user is actively waiting for and that takes 30ms take 25ms instead. That's wasted money on developer time.

If your "user" is a developer of embedded software with memory constraints and using your library leaves them more room that's awesome. If your user was someone using the library on a general purpose computing device with loads of memory then the 2 vs. 5 does nothing.

I decided not put it off for later, and keep things simple for now.

Who was talking about a single millisecond here?

I notice, broadly, two types of people who engage in these arguments.

1> OMG, computers are thousands of times faster than they were a decade ago, why is everything not lightning fast? Why are so many things slower than they were back then? Why is my chat program eating 2GB(!) of RAM?

2> Because we're busy writing six billion features on our Nth iteration of this problem space, we can't be bothered to shave a few millis bro!

And they just talk past each other.

And when you do identify the 1%, you need to be testing optimizations with a profiler constantly while optimizing. Profile. Do some optimization. Profile again. Roll back if not successful. Repeat until done. It's impossible to optimize well if you're not doing profiling.

The ultimate tools would be either Intel's profiling tools, or ARM's profiling suite (both very expensive). But MSVC and GCC do a fantastic job of scheduling instructions to avoid pipeline stalls these days, so these deep profiling tools are unlikely to gain more than 2 or 3% performance increases these days. (Worthwhile pretty much only if you're writing GPU drivers for NVidia or AMD).

Taken as a given that 100% of your code is at least algorithmically correct in the first place. (Appropriately better than O(N^2) whenever possible).

- Former writer of graphics drivers, currently audio DSP engineer.

[1] https://github.com/KDAB/hotspot

[2] https://github.com/KDAB/hotspot#off-cpu-profiling

VTune allows you to determine where pipeline stalls are occurring at the instruction level (for that last 2 or 3% gain in performance). I haven't worked with ARM profilers (way out of my price range), but I assume, given the exorbitant price, they provide the same sort of in-depth analysis. Probably a handful of people on the planet that need that kind of in-depth analysis.

If you can't recognize the percent where it matters a lot, clearly that percent does not exist and you're bothering about nothing.

I see a lot of talk about the importance of tuning Formula 1 cars in a world where everyone drives ford fiestas.

If you're lucky enough to eat your own dogfood, run unit tests against a copy(!) of your in-house database. A utility to anonymize the data was a fairly significant investment, but absolutely worth it in the long run. Being able to run and monitor benchmark unit tests for selected critical operations on enterprise-scale test data as part of the continuous-build process: fabulous!

How this typically works with performance is very similar, with a small team working to identify problematic areas where optimization would drive the highest impact, and the rest of the organization keeping performance in mind but not otherwise concerned with it in their day-to-day work.

But overall, I think you overestimate how much time you spend loading the website and how much time it's just sitting there, mostly idle.

And in the end, as long as it's fast enough that users don't stop using the site/webapp/program/whatever, then it's fine, imho. When it becomes too slow, the developers will be asked to improve performance. Because in the end, economics is the driver, not performance.

This is separate from the discussion about tradeoffs between flexible design patterns and low-level performance.

reading the website is productive. Waiting on it to load is not.

I'd rather have app burn a whole core whole time if it cut 1s off load time when clicking something.

2s you notice as a user. 50ms you won't. In fact even 500ms you won't notice too much but we are getting close to where optimization will be noticeable to a user.

https://www.marketingdive.com/news/google-53-of-mobile-users...

Unless we’re talking about specific compute-intensive websites, this is almost certainly network loading latency.

Modern web browsers are very fast. Moderns CPUs are very fast. Common, random websites aren’t churning through “multiple seconds” of CPU time just to render.

I use Jira every day and, no, it does not take 30-60 seconds to load a page.

The hyperbole in this comment section is something else. Either that or people are using 15 year old computers to browse the web.

- Loading: 29ms with uBlock vs 42ms without

- Scripting: 548ms vs 1850ms (!!)

- Rendering: 42ms vs 105ms

- Painting: 8ms vs 29ms

- System: 216ms vs 295ms

- Idle: 460ms vs 8707ms

Holy shit, advertising and trackers are absolute resource hogs.

So if you were to manually run a for loop over an array instead of iterating through it I'm not surprised you got an order of magnitude faster performance.

In JavaScript on the other hand it handles the abstraction by constructing a separate function for each pattern you use. In those functions it allocates an array the same size as the working set, iterates through each element, then returns the new array. If you're doing multiple operations at once this means that you have to have multiple allocations and multiple iterations through the entire working set.

Because it's doing an allocations it's basically doing an extra memcpy for each additional pattern past one which is a giant slowdown. Then if the working set is too big for the L2 cache it needs to be reloaded from L3 each loop. If the working set is too big for L3 then it needs to reload from main memory EACH TIME.

If you wanted to implement patterns as slow as molasses I can think of no better way than to sugar it out like JavaScript did.

I’ve personally spent many hours doing performance analysis, triage and remediation on websites built using modern tech stacks that had inadvertently exchanged UX for DX. Too much JS sent over the wire can definitely tie up the browser’s main thread for whole seconds even on desktop, though in my experience it’s much more common on mobile. This situation can be difficult to correct depending on the abstractions, organization and overall architecture you chose early on, and code-spitting and dead code elimination won’t always fix what’s broken.

My most recent misadventure: trying to write hand-coded ARM Neon assembler, and/or C++ code with neon intrinsics to optimize a piece of real-time audio effect code. The clear performance winner: plain C++ with no intrinsics, but tweaked to allow auto-vectorization (plus judicious use of the __restrict modifier for a small but significant boost). GCC produced code that had better instruction scheduling than I could (but not for the NEON intrinsics, oddly). And as an added bonus, the same plain-old C++ code generates AVX vectorization on MSVC without modifications! (MSVC also supports __restrict until the C++ standards committee gets their act together to adopt the eminently necessary C99 restrict keyword).