7 ms·

But it has such a cool name! Sure mrg32k3a has a smaller state, runs faster and has a quick skip ahead function but L'Ecuyer just didn't put enough effort into

But it has such a cool name! Sure mrg32k3a has a smaller state, runs faster and has a quick skip ahead function but L'Ecuyer just didn't put enough effort into the marketing.

Asooka 6y ago
Hm, "Mister G"?
ajross 6y ago
Had to look it up to check, but it's not marketing. That function is part of a family that requires double precision floating point. So "runs faster" is a bit spun relative to a 32 bit integer function. Sure it does, on your desktop CPU.
- josephg 6y ago
  My new phone is faster than my current desktop CPU. Faster everywhere except in embedded applications is still pretty compelling!
  - ajross 6y ago
    But your thermostat is not, and it probably needs a PRNG too.
    - quiescant_dodo 6y ago
      I'm honestly curious why any non-smart thermostat would need a PRNG. Can you give examples why it would be needed? I'm assuming my thermostat is a input-output machine where the input is detected ambient temperature (computed internal to the device) and the output is either RUN_FURNACE or DO_NOT_RUN_FURNACE.
      - garmaine 6y ago
        Many boring, everyday algorithms employ random choice or blinded inputs to prevent worst case execution.
        alanbernstein 6y ago
        Though I'm sure that's true, a simple thermostat can be built without any electronic components at all, using only the simplest of analog mechanisms, so it's hard to see how it's relevant.
        317070 6y ago
        Well, these days they are actually often connected to the internet. That on its own requires prngs.
        carlmr 6y ago
        I think the point was that if they're fast enough to connect to the internet they will be fast enough to calculate PRNGs. If they're not connected to the internet, they don't need them.
        raverbashing 6y ago
        So it needs a PRNG, but not a cryptographically secure one
        deleted 6y ago
        [deleted]
    - sdenton4 6y ago
      Luckily, if it's anything like MY thermostat, the detected temperature is itself a PRNG.
      - antonvs 6y ago
        The idea of a thermostat using its own detected temperature as a random input to help set the temperature would be horrifying, if I weren't already convinced that that's how mine works.
      - GuB-42 6y ago
        It is actually a true RNG. Thermal noise, or whatever is messing up with your thermostat can be used as a source of entropy by hardware RNGs.
- pkhuong 6y ago
  mrg32k3a uses double float for integer arithmetic because it was designed (like poly1305) back when computers were mostly 32 bit, and C compilers didn't reliably expose 64 bit operations. It's easy to implement with 32-bit integer arithmetic in assembly, and trivial in C with 64-bit integers.
loeg 6y ago
PCG is the way to go. Small state requirements, very fast, good distribution: https://www.pcg-random.org/index.html https://www.pcg-random.org/index.html
- SeanLuke 6y ago
  PCG has had no peer review of its author's claims at all, and some of those claims are dubious. PRNGs are serious things and require serious deliberation.
  - loeg 6y ago
    That’s not true? BigCrush and PractRand results have been (trivially) reproduced, performance is also easy to verify. What claims are dubious? Everything about PCG strikes me as serious and deliberate.
  - derbOac 6y ago
    That's not technically true. The history of the peer review process is outlined here: https://www.pcg-random.org/posts/history-of-the-pcg-paper.html https://www.pcg-random.org/posts/history-of-the-pcg-paper.ht... I'm confused about why the author didn't just resubmit it elsewhere, but to me PCG as an example raises a lot of questions about the value of peer review today, and about how it is conducted (not that I think it does or doesn't have value, but it raises a lot of questions about it). At least from the author's perspective it seems the concerns were about presentation rather than substance. Speaking from personal experience, peer review can be quixotic and I put little weight on it not appearing in a peer-reviewed journal, as opposed to any specific criticisms that might have been raised in a review (given the attention to PCG at this point, if there were serious criticisms of it it seems a failing on the part of the journal not to address these).
    - nsajko 6y ago
      > That's not technically true. So your argument is that rejection from peer-review counts as peer-review? > I'm confused about why the author didn't just resubmit it elsewhere [...] concerns were about presentation rather than substance As far as I understand, the PCG paper is double the size it should be to get accepted by a serious journal. It contains a lot of unnecessary explanations of basic facts, making it unnecessarily tiresome to read for an expert. Presentation matters, because it stands between you and the substance, and you have to be able to get to the substance as fast as possible to review the paper. > [...] (given the attention to PCG at this point, if there were serious criticisms of it it seems a failing on the part of the journal not to address these). Well, the paper was rejected before it could come to that point...
throwaway_pdp09 6y ago
Great comment. In a world overrun by marketeers, polluted by image over substance, someone calls for more and on HN of all places.
- permo-w 6y ago
  I think the comment is meant to be joke expressing the exact concerns you are raising

But it has such a cool name! Sure mrg32k3a has a smaller state, runs faster and has a quick skip ahead function but L'Ecuyer just didn't put enough effort into the marketing.

Asooka 6y ago

Hm, "Mister G"?

ajross 6y ago

Had to look it up to check, but it's not marketing. That function is part of a family that requires double precision floating point. So "runs faster" is a bit spun relative to a 32 bit integer function. Sure it does, on your desktop CPU.

josephg 6y ago
My new phone is faster than my current desktop CPU. Faster everywhere except in embedded applications is still pretty compelling!
- ajross 6y ago
  But your thermostat is not, and it probably needs a PRNG too.
  - quiescant_dodo 6y ago
    I'm honestly curious why any non-smart thermostat would need a PRNG. Can you give examples why it would be needed? I'm assuming my thermostat is a input-output machine where the input is detected ambient temperature (computed internal to the device) and the output is either RUN_FURNACE or DO_NOT_RUN_FURNACE.
    - garmaine 6y ago
      Many boring, everyday algorithms employ random choice or blinded inputs to prevent worst case execution.
      - alanbernstein 6y ago
        Though I'm sure that's true, a simple thermostat can be built without any electronic components at all, using only the simplest of analog mechanisms, so it's hard to see how it's relevant.
        317070 6y ago
        Well, these days they are actually often connected to the internet. That on its own requires prngs.
        carlmr 6y ago
        I think the point was that if they're fast enough to connect to the internet they will be fast enough to calculate PRNGs. If they're not connected to the internet, they don't need them.
      - raverbashing 6y ago
        So it needs a PRNG, but not a cryptographically secure one
        deleted 6y ago
        [deleted]
  - sdenton4 6y ago
    Luckily, if it's anything like MY thermostat, the detected temperature is itself a PRNG.
    - antonvs 6y ago
      The idea of a thermostat using its own detected temperature as a random input to help set the temperature would be horrifying, if I weren't already convinced that that's how mine works.
    - GuB-42 6y ago
      It is actually a true RNG. Thermal noise, or whatever is messing up with your thermostat can be used as a source of entropy by hardware RNGs.
pkhuong 6y ago
mrg32k3a uses double float for integer arithmetic because it was designed (like poly1305) back when computers were mostly 32 bit, and C compilers didn't reliably expose 64 bit operations. It's easy to implement with 32-bit integer arithmetic in assembly, and trivial in C with 64-bit integers.

loeg 6y ago

PCG is the way to go. Small state requirements, very fast, good distribution: https://www.pcg-random.org/index.html https://www.pcg-random.org/index.html

SeanLuke 6y ago
PCG has had no peer review of its author's claims at all, and some of those claims are dubious. PRNGs are serious things and require serious deliberation.
- loeg 6y ago
  That’s not true? BigCrush and PractRand results have been (trivially) reproduced, performance is also easy to verify. What claims are dubious? Everything about PCG strikes me as serious and deliberate.
- derbOac 6y ago
  That's not technically true. The history of the peer review process is outlined here: https://www.pcg-random.org/posts/history-of-the-pcg-paper.html https://www.pcg-random.org/posts/history-of-the-pcg-paper.ht... I'm confused about why the author didn't just resubmit it elsewhere, but to me PCG as an example raises a lot of questions about the value of peer review today, and about how it is conducted (not that I think it does or doesn't have value, but it raises a lot of questions about it). At least from the author's perspective it seems the concerns were about presentation rather than substance. Speaking from personal experience, peer review can be quixotic and I put little weight on it not appearing in a peer-reviewed journal, as opposed to any specific criticisms that might have been raised in a review (given the attention to PCG at this point, if there were serious criticisms of it it seems a failing on the part of the journal not to address these).
  - nsajko 6y ago
    > That's not technically true. So your argument is that rejection from peer-review counts as peer-review? > I'm confused about why the author didn't just resubmit it elsewhere [...] concerns were about presentation rather than substance As far as I understand, the PCG paper is double the size it should be to get accepted by a serious journal. It contains a lot of unnecessary explanations of basic facts, making it unnecessarily tiresome to read for an expert. Presentation matters, because it stands between you and the substance, and you have to be able to get to the substance as fast as possible to review the paper. > [...] (given the attention to PCG at this point, if there were serious criticisms of it it seems a failing on the part of the journal not to address these). Well, the paper was rejected before it could come to that point...

throwaway_pdp09 6y ago

Great comment. In a world overrun by marketeers, polluted by image over substance, someone calls for more and on HN of all places.

permo-w 6y ago
I think the comment is meant to be joke expressing the exact concerns you are raising