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How much your computer can do in a second

computers-are-fast.github.io

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Re: How much your computer can do in a second

#61

Post by geogriffin »

dragontamer wrote: post #25
gizmo wrote: post #12

Pretty cool, but a number of the questions are totally unknowable. For instance the question about web requests to google. Depending on your internet connection you've got more than a order of magnitude difference in the outcome. In the question about SSD performance the only hint we have is that the computer has "an SSD", but a modern PCIe SSD like in the new Macbook pro is over 10 times faster than the SSDs we got…

This is exactly my main complaint about this. Still, it was an intriguing idea, even if a lot of the answers were based on things not described. I did learn a few things... I don't do much parsing so I didn't realize how slow JSON was compared to other packaged formats.

it's the required escaping of quotation marks!! if you have non-english users and didn't turn off escaping of non-ascii then you're in for a real surprise :) length-prefixed strings would solve this.

also, memory allocation penalties can hit you hard, depending on your environment, since it's hard to predict what you'll need to allocate when encoding / decoding json

Re: How much your computer can do in a second

#62

Post by pekk »

userbinator wrote: post #13

Alternatively, this could be titled "do you know how much your computer could do in a second but isn't because of bad design choices, overengineered bloated systems, and dogmatic adherence to the 'premature optimisation' myth?" Computers are fast, but not if all that speed is wasted. A recent related article: https://news.ycombinator.com/item?id=13940014

Do you know how much you could do in a month but can't because of bad design choices, overengineered type systems, and dogmatic adherence to the 'every application needs to be written in the language with the best benchmark numbers' myth?

Re: How much your computer can do in a second

#63

Post by DesiLurker »

p1esk wrote: post #3
dom0 wrote: post #2

More impressively, sum.c could go likely an order of magnitude or so faster, when optimized. > Friends who do high performance networking say it's possible to get network roundtrips of 250ns (!!!), Well stuff like Infiniband is less network, and more similar to a bus (e.g. RDMA, atomic ops like fetch-and-add or CAS). > write_to_memory.py Is also interesting because this is dominated by inefficiencies in the API and i…

How would you optimize sum.c to be faster?

for a data parallel problem like that you could vectorize it using the SIMD unit. It never ceases to amaze me at any point how much of silicon real estate just sits idle because no one really bothered to look behind the curtain and tailor the code for a specific architecture. for reference, a recent Intel chip will have 256b wide vector unit (512 for server class chips) that can be treated as a vector of 8/16/32/64b units to do parallel math. at a typical 16b ops you get 16x speedup for practically nothing. plus its considerably more if you have predictable but non standard data access patterns.

now IMO what the parent commenter was trying to say is often this punchline about premature optimizations used as catch-all justification for all the convenience/expediency related decisions taken. & also it just works well to create future work. unfortunately that never gets scheduled as I have seen management time frame shrink too. almost everyone is in quick & dirty 'working' version to book a success and move on. with this culture if you try to push resolving these 'technical debt' type issues you are just perceived as a downer.

Re: How much your computer can do in a second

#64

Post by gravypod »

halomru wrote: post #51
dom0 wrote: post #49

Earlier quoted context omitted.

> You can't really do loop unrolling and constant folding as some suggest because the number of iterations is determined at run time. Huh?

That question is a bit unspecific :D >NUMBER = atoi(argv[1]); argv is populated at runtime based on what the OS passed you. But you are right if you meant that my statement is too strong: you can't do arbitrary loop unrolling. You can jump to a loop that's unrolled once if the number is even, etc. There are certainly also optimizers that will just output the input without any loop, but that's beyond anything I would…

If you are going from 0 -> NUMBER and adding one to a variable every iteration, what will the variable's final result be? NUMBER. The compiler can see this and will just do the following:

    s = i = atoi(argv[1]);
Now the loop is gone.

Edit: This will still happen even if you're doing other stuff in there. GCC will attempt to inline and optimize like this. If it is impossible then you will see a loop with most of the stuff factored out of it.

Re: How much your computer can do in a second

#65

Post by jdblair »

dahart wrote: post #34
userbinator wrote: post #13

Alternatively, this could be titled "do you know how much your computer could do in a second but isn't because of bad design choices, overengineered bloated systems, and dogmatic adherence to the 'premature optimisation' myth?" Computers are fast, but not if all that speed is wasted. A recent related article: https://news.ycombinator.com/item?id=13940014

To be fair, that article is discussing a small bug, not over engineering or dogma. The size of the deal people made over it was more wasteful than the CPU time this (now fixed) bug cost. And FWIW, of all the problems that matter to me and my teams, I find premature optimization to be far, far more wasteful of money and human energy than wasted CPU cycles. There are definitely times to worry about performance, and I f…

Its always about making the right judgement call between optimization and complexity, and sometimes I'm still surprised by what needs optimized and what doesn't.

An anecdote from a project I'm working on. I'm writing some LED control software for light shows and using GPIO pins on various embedded Linux boards (CHiP, Raspberry Pi, Orange Pi) to generate the SPIO-like serial signal I need.

My first draft, for Raspberry Pi 3, is a wonder of compact bit twiddling, doing all the necessary operations to write to GPIO memory in one compact function.

For the second platform, the Orange Pi Zero, I found a Python library for GPIO access that someone had already written, saw that the gpio operations were broken out into separate files and pulled those files into my project. My first thought: this will never be fast enough, and the O-Pi Zero is slower than the R-Pi 3. Luckily, I decided to try it first.

Now the the gory details of writing to memory are hidden in the library and the logic in my code to generate clock pulses and write bits is a lot more clear. I had to tune the code differently - the delays in my code to generate the correct clock pulse width are shorter now that there is function call overhead, but that was easy to sort out with a bit of trial-and-error with a logic analyzer.

Re: How much your computer can do in a second

#66

Post by sametmax »

userbinator wrote: post #13

Alternatively, this could be titled "do you know how much your computer could do in a second but isn't because of bad design choices, overengineered bloated systems, and dogmatic adherence to the 'premature optimisation' myth?" Computers are fast, but not if all that speed is wasted. A recent related article: https://news.ycombinator.com/item?id=13940014

It's wasted only if it's not traded for something else. But it is.

A lot of system would simply not exist if we would have waited for people doing it properly because there is a limited pool of very skilled experts and the demand for IT far exceed our ability to supply. Plus writing good code takes a lot of time and resources, but our society changes now so fast that it very well maybe rewritten next year.

Hence, we are trading computer power to compensate our limited human resource.

E.G: wondering why you see electron apps everywhere now ? Because until now making a beautiful, powerful and modern app with a portable GUI was something only a few people would be able to do. Now any web dev can do it, and they are able to solve problems that weren't solved before because nobody would be available to do it. At the price of performance, memory usage and the use of the ugliest programming language we ever made popular.

It's the same deal as before. When C arrived, Wordperfect died because they stick to assembly. For them, C was wasting resources.

When Java arrived, expert systems were turned to it because it was more productive than to write it in C. We didn't need it to be fast, but the companies wanted their tools to be produced quickly.

Then when the Web arrived, people were laughing about the quality of PHP (initially a Perl hack !). So many bad code, so many security fails, just a terrible, terrible stack of programming debt. But it created the web we have today because it was easy to use, and suddenly a lot of people could just write their web forum. Hell, I learned my job with EasyPhp.exe way before becoming a Python expert.

Nothing here is wasted. It's just implicitly and involuntarily invested.

Re: How much your computer can do in a second

#67

Post by mwcampbell »

pekk wrote: post #62
userbinator wrote: post #13

Alternatively, this could be titled "do you know how much your computer could do in a second but isn't because of bad design choices, overengineered bloated systems, and dogmatic adherence to the 'premature optimisation' myth?" Computers are fast, but not if all that speed is wasted. A recent related article: https://news.ycombinator.com/item?id=13940014

Do you know how much you could do in a month but can't because of bad design choices, overengineered type systems, and dogmatic adherence to the 'every application needs to be written in the language with the best benchmark numbers' myth?

False dichotomy. The real solution is a language with a strong, static type system (and thus plenty of room for ahead-of-time optimization) that's also concise and productive, such as Kotlin or Swift.

Re: How much your computer can do in a second

#68

Post by EvilTerran »

halomru wrote: post #51
dom0 wrote: post #49

Earlier quoted context omitted.

> You can't really do loop unrolling and constant folding as some suggest because the number of iterations is determined at run time. Huh?

That question is a bit unspecific :D >NUMBER = atoi(argv[1]); argv is populated at runtime based on what the OS passed you. But you are right if you meant that my statement is too strong: you can't do arbitrary loop unrolling. You can jump to a loop that's unrolled once if the number is even, etc. There are certainly also optimizers that will just output the input without any loop, but that's beyond anything I would…

Well, you could do arbitrary loop unrolling - with Duff's Device:

https://en.wikipedia.org/wiki/Duffs_device

Re: How much your computer can do in a second

#69

Post by em3rgent0rdr »

gizmo wrote: post #20
agumonkey wrote: post #17

Earlier quoted context omitted.

The market is wasteful. Lots of things are subpar because of the competition requiring adhoc solutions pushed to market, then becoming standard, so on and so forth. You can blame the game or not. At least if there was some acknowledgement of that process and a little cleanup time to spread good ideas and good fix ... Personally I always feel weird booting up old boxes (say old = Pentium 2) and realizing how much the…

An eye-opening experience is running an IDE like Visual Studio 6 or a really old version of Photoshop on a modern machine. It starts instantly, compile times are a fraction of what we're used to. The interface is totally responsive. It's remarkable how much better software feels when everything is instant.

It's remarkable how much better software feels when the software was developed on a slow machine.

Unfortunately devs invest in the fastest equiplent, so they don't experience how their code runs on the average end user who doesn't upgrade every couple years.

In can be useful to test your code in a VM that is deliberately slowed down, so can get a feel for user experience on a slower machine. Then you'll know what parts need to be optimized.

Re: How much your computer can do in a second

#70

Post by jdblair »

jdblair wrote: post #65
dahart wrote: post #34

Earlier quoted context omitted.

To be fair, that article is discussing a small bug, not over engineering or dogma. The size of the deal people made over it was more wasteful than the CPU time this (now fixed) bug cost. And FWIW, of all the problems that matter to me and my teams, I find premature optimization to be far, far more wasteful of money and human energy than wasted CPU cycles. There are definitely times to worry about performance, and I f…

Its always about making the right judgement call between optimization and complexity, and sometimes I'm still surprised by what needs optimized and what doesn't. An anecdote from a project I'm working on. I'm writing some LED control software for light shows and using GPIO pins on various embedded Linux boards (CHiP, Raspberry Pi, Orange Pi) to generate the SPIO-like serial signal I need. My first draft, for Raspberr…

Something else I've learned the hard way - sometimes its better to cut and paste the same short code snippet in multiple places than create an abstraction to put the code in one place. I admit this is probably an indication there's a problem in the overall design, but sometimes those design choices have already been made and the goal is to make things work with what I have.
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