4 ms·

I think there's an interesting distinction here between general-purpose software and single-use code. General-purpose software has many users with many kinds o

by panic 11y ago

I think there's an interesting distinction here between general-purpose software and single-use code. General-purpose software has many users with many kinds of data. Unless your domain is intrinsically limited, it's impossible to be "fast enough" -- you can always find some data that your code will take to long to process. There's always an incremental benefit to optimization, and with enough users, it's irresponsible to waste collective years of people's time by leaving performance on the table. What you've said makes perfect sense for one-off simulations, however. And in practice, optimizers are designed to make tight numerical code run fast. I don't think your use case will ever be ignored. It's just that most systems today are not made of tight loops of arithmetic operations. We need more tools to optimize the kind of code that actually makes our computers slow: code that allocates and deallocates memory, code that transforms data between different formats, code that constructs and operates on complex data structures -- that sort of thing.

valm- 11y ago
I don't entirely disagree, but I would like to make one point. Taking 1 millisecond from 1000 people, does not translate to 1 second of lost human productivity. There's no way to collect all those little slices of time and they are not appreciable individually. (Assuming those milliseconds are sufficiently spread out, i.e., not 1 ms out of every 2, or something like that)
- modeless 11y ago
  > Taking 1 millisecond from 1000 people, does not translate to 1 second of lost human productivity I believe that it does. If you average over a large population even tiny imperceptible increases in e.g. page load time have a measurable effect. Perhaps 1000 people isn't a large enough sample to measure the effect from 1ms delay considering all the confounding factors at play, but I absolutely believe you could see it with precise enough measurement and a large enough sample.
  - Rebelgecko 11y ago
    Reminds me of this semi-relevant story about improving the boot times of the original Macintosh — http://www.folklore.org/StoryView.py?story=Saving_Lives.txt http://www.folklore.org/StoryView.py?story=Saving_Lives.txt
    - gaius 11y ago
      The irony being that Jobs himself limited the memory in the original Mac, so it would have to go to disk more often!
      - jedrek 11y ago
        Source?
        gaius 11y ago
        Its a fairly well known story. The engineers ignored him and built in capability for 512k anyway. http://www.informationweek.com/mobile/mobile-devices/steve-jobs-jerry-pournelle-reflects/d/d-id/1099842 http://www.informationweek.com/mobile/mobile-devices/steve-j... He also hated fans and expansion slots.
  - darkmighty 11y ago
    Hmm I think the heart of the question is whether productivity is linear with time. I guess he's right that, for small values of t, productivity is highly superlinear. So giving 1 person an extra minute has an impact on that person, but because of superlinearity, if you distribute that among 60 persons the extra second won't allow anything new, like an original thought or whatever.
    - modeless 11y ago
      You're thinking about it wrong. Of course if you give 60 people 1 second each they won't be able to accomplish a task that takes a minute; that's obvious. Instead what if you give a group of people 59 seconds each to complete a task that takes 1 minute +-10 seconds, and then you give a different group of people 60 seconds each to complete the same task. More people in the second group will complete the task.
- xioxox 11y ago
  However the carbon footprint of the code does reduce like that. It would be very wasteful in terms of energy not to optimize a widely used binary.
  - loup-vaillant 11y ago
    Beware: optimising for speed and optimising for energy don't yield the same results. If you want speed, you typically want to use your CPU as much as possible. If you want to save energy, you'll want to underclock your CPU. If we go all the way to hardware design, saving energy means going massively multicore, with simple, slow, in-order cores. You can optimise both, to some extent. But there is a point where you have to chose one or the other.
    - exDM69 11y ago
      > If you want to save energy, you'll want to underclock your CPU. This is incorrect. To save energy, the strategy is to do your thing as quickly as possible, with maximum CPU clocks and enter power saving mode as soon as possible. Otherwise the leakage current in the CPU will consume more energy than can be saved by underclocking. It may be counterintuitive but fast code consumes the least energy.
      - loup-vaillant 11y ago
        I insist: speed and energy savings are correlated to a point. To. A. Point. Some instructions in your CPU may be faster, but slower alternative often consume less total energy (even taking everything into account —there have been experiments and power measurements). Even if it means your CPU is up a bit longer. Then there are considerations that save energy, but don't matter for speed at all, such as the width of integer operations: no need to go 32 bits wide or 64 bits wide, when no value exceeds 127. Also, I'm not sure about current leakage exceeding the benefits of underclocking. Those benefits are massive. Lowering the frequency also means you can lower the voltage. In the talks I have seen, halving the speed of a core (and lowering the voltage accordingly) makes it dissipate about a fourth the power. Half the energy, considering everything takes twice the time. This of course ignores leakage, but I doubt it would counter such a strong effect. Besides, with a phone running a number of background processes, I wonder how much power saving time you can get. Not to mention, the potential costs of switching in and out of CPU saving mode.
chriswarbo 11y ago
> There's always an incremental benefit to optimization, and with enough users, it's irresponsible to waste collective years of people's time by leaving performance on the table. I could just as easily claim that skilled developer's time is a precious resource, and it's irresponsible to waste it squeezing out performance when so much software still remains unwritten.
- bostik 11y ago
  There's another side to that, as well. Developers' time is expensive, and the time it takes to get feedback from code runs adds up when you have lots of developers. Especially if the roundtrip times are short enough not to allow switching between tasks, but long enough to cause constant "wall time waits". I'd be more than willing to have couple of extremely skilled developers profile and optimise the common code so that the feedback loop becomes shorter for everyone. That way more of the yet-unwritten software might just be tackled. My old boss once had me spend more than a week packaging and streamlining our access VPN configurations. When I asked him about it some time later, he explained that even though I was away from billable projects for that time, it would have cost a whole lot more overall to have all our developers and managers massage their setups every time something changed. Large figures are sums of lots of small figures...

by panic 11y ago

valm- 11y ago

I don't entirely disagree, but I would like to make one point. Taking 1 millisecond from 1000 people, does not translate to 1 second of lost human productivity. There's no way to collect all those little slices of time and they are not appreciable individually. (Assuming those milliseconds are sufficiently spread out, i.e., not 1 ms out of every 2, or something like that)

modeless 11y ago
> Taking 1 millisecond from 1000 people, does not translate to 1 second of lost human productivity I believe that it does. If you average over a large population even tiny imperceptible increases in e.g. page load time have a measurable effect. Perhaps 1000 people isn't a large enough sample to measure the effect from 1ms delay considering all the confounding factors at play, but I absolutely believe you could see it with precise enough measurement and a large enough sample.
- Rebelgecko 11y ago
  Reminds me of this semi-relevant story about improving the boot times of the original Macintosh — http://www.folklore.org/StoryView.py?story=Saving_Lives.txt http://www.folklore.org/StoryView.py?story=Saving_Lives.txt
  - gaius 11y ago
    The irony being that Jobs himself limited the memory in the original Mac, so it would have to go to disk more often!
    - jedrek 11y ago
      Source?
      - gaius 11y ago
        Its a fairly well known story. The engineers ignored him and built in capability for 512k anyway. http://www.informationweek.com/mobile/mobile-devices/steve-jobs-jerry-pournelle-reflects/d/d-id/1099842 http://www.informationweek.com/mobile/mobile-devices/steve-j... He also hated fans and expansion slots.
- darkmighty 11y ago
  Hmm I think the heart of the question is whether productivity is linear with time. I guess he's right that, for small values of t, productivity is highly superlinear. So giving 1 person an extra minute has an impact on that person, but because of superlinearity, if you distribute that among 60 persons the extra second won't allow anything new, like an original thought or whatever.
  - modeless 11y ago
    You're thinking about it wrong. Of course if you give 60 people 1 second each they won't be able to accomplish a task that takes a minute; that's obvious. Instead what if you give a group of people 59 seconds each to complete a task that takes 1 minute +-10 seconds, and then you give a different group of people 60 seconds each to complete the same task. More people in the second group will complete the task.
xioxox 11y ago
However the carbon footprint of the code does reduce like that. It would be very wasteful in terms of energy not to optimize a widely used binary.
- loup-vaillant 11y ago
  Beware: optimising for speed and optimising for energy don't yield the same results. If you want speed, you typically want to use your CPU as much as possible. If you want to save energy, you'll want to underclock your CPU. If we go all the way to hardware design, saving energy means going massively multicore, with simple, slow, in-order cores. You can optimise both, to some extent. But there is a point where you have to chose one or the other.
  - exDM69 11y ago
    > If you want to save energy, you'll want to underclock your CPU. This is incorrect. To save energy, the strategy is to do your thing as quickly as possible, with maximum CPU clocks and enter power saving mode as soon as possible. Otherwise the leakage current in the CPU will consume more energy than can be saved by underclocking. It may be counterintuitive but fast code consumes the least energy.
    - loup-vaillant 11y ago
      I insist: speed and energy savings are correlated to a point. To. A. Point. Some instructions in your CPU may be faster, but slower alternative often consume less total energy (even taking everything into account —there have been experiments and power measurements). Even if it means your CPU is up a bit longer. Then there are considerations that save energy, but don't matter for speed at all, such as the width of integer operations: no need to go 32 bits wide or 64 bits wide, when no value exceeds 127. Also, I'm not sure about current leakage exceeding the benefits of underclocking. Those benefits are massive. Lowering the frequency also means you can lower the voltage. In the talks I have seen, halving the speed of a core (and lowering the voltage accordingly) makes it dissipate about a fourth the power. Half the energy, considering everything takes twice the time. This of course ignores leakage, but I doubt it would counter such a strong effect. Besides, with a phone running a number of background processes, I wonder how much power saving time you can get. Not to mention, the potential costs of switching in and out of CPU saving mode.

chriswarbo 11y ago

> There's always an incremental benefit to optimization, and with enough users, it's irresponsible to waste collective years of people's time by leaving performance on the table. I could just as easily claim that skilled developer's time is a precious resource, and it's irresponsible to waste it squeezing out performance when so much software still remains unwritten.

bostik 11y ago
There's another side to that, as well. Developers' time is expensive, and the time it takes to get feedback from code runs adds up when you have lots of developers. Especially if the roundtrip times are short enough not to allow switching between tasks, but long enough to cause constant "wall time waits". I'd be more than willing to have couple of extremely skilled developers profile and optimise the common code so that the feedback loop becomes shorter for everyone. That way more of the yet-unwritten software might just be tackled. My old boss once had me spend more than a week packaging and streamlining our access VPN configurations. When I asked him about it some time later, he explained that even though I was away from billable projects for that time, it would have cost a whole lot more overall to have all our developers and managers massage their setups every time something changed. Large figures are sums of lots of small figures...