Random number generator is unbelievably bad.

[whesse]

The Dart VM pseudorandom number generator is very very bad. It generates
approximately one pseudorandom bit per call. The bits of consecutive random numbers are almost all the same, just shifted. We should copy the V8 random number generator, or some other one that works better. Here is the output of printing consecutive random numbers, in binary, followed by the code that does so:

                 100100000000011
     100100000000010010000000001
     110110000000001001000000000
     111111000000000100100000000
      11111100000000010010000000
     101011110000000001001000000
     110001111000000000100011111
      11000111100000000010001111
       1100011110000000001000111
        110001111000000000100011
         11000111100000000010001
          1100011110000000001000
           110001111000000000100
            11000111100000000010
             1100011110000000001
              110001111000000000
     100100000011000111100000000
      10010000001100011110000000
       1001000000110001111000000
     100000100000011000111011111
      10000010000001100011101111
       1000001000000110001110111
        100000100000011000111011
         10000010000001100011101
          1000001000000110001110
           100000100000011000111
            10000010000001100011
             1000001000000110001
              100000100000011000
     100100000010000010000001100
     110110000001000001000000110
     111111000000100000100000011
     111011100000010000010000001
      11101110000001000001000000
       1110111000000100000100000
        111011100000010000010000
     100111101110000001000001000
     110111110111000000100000011
      11011111011100000010000001
       1101111101110000001000000
        110111110111000000100000
         11011111011100000010000

void main() {
  for (var i=0 ; i < 100 ; ++i) {
    var binary = (Math.random() * 0x8000000).toInt().toRadixString(2);
    while (binary.length < 32) {
      binary = " " + binary;
    }
    print(binary);
  }
}

[iposva-google]

Set owner to @iposva-google.

[DartBot]

This comment was originally written by [email protected]

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Added Triaged label.

[iposva-google]

Added Accepted label.

[DartBot]

This comment was originally written by [email protected]

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The V8 PNG is pretty good - I worked on it recently. I would recommend it. The question of how to seed Isolates, so they aren't predictable, and how to replay with a predictable seed, for testing, should also be addressed.

[DartBot]

This comment was originally written by [email protected]

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Issue #771 has been merged into this issue.

[DartBot]

This comment was originally written by [email protected]

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Issue #245 has been merged into this issue.

[floitschG]

Issue #1983 might be another duplicate.

[whesse]

Issue #1983 has been merged into this issue.

[DartBot]

This comment was originally written by [email protected]

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@whess ... seeding the built-in random number generator should not be allowed... this ends up reducing flexibility of implementation. Code needing deterministic numbers for testing should accept a random number generator as an input. This dependency injection will allow you to get a deterministic sequence without locking the language implementation into a given PRNG.

[sethladd]

FYI this came up on the mailing list again today: https://groups.google.com/a/dartlang.org/group/misc/browse_thread/thread/b872ef7b23c03237#

[jmesserly]

upping to high pri ... this breaks just about every app that tries to do simulation ... physics, games, etc :)

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Removed Priority-Medium label.
Added Priority-High label.

[dgrove]

Issue #2805 has been merged into this issue.

[iposva-google]

Sorry, I should have marked this as started as of about a week ago. We had been evaluating different approaches and I expect to have something ready in about a week.

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Added Started label.

[DartBot]

This comment was originally written by [email protected]

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This just happened to me in the hackathon.

[sigmundch]

Added Isolates label.

[DartBot]

This comment was originally written by [email protected]

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Any progress? First thing I tried in Dart was random and .. well.. not so much.

[floitschG]

Ivan uploaded a CL for review: https://chromiumcodereview.appspot.com/10389150/
I expect it to land next week.

[whesse]

Issue #3463 has been merged into this issue.

[DartBot]

This comment was originally written by [email protected]

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I have a Mersenne twister implementation, if it would help anyone. (Copyright restrictions mean that I can contribute it to Dart easily but would require additional time to submit elsewhere.) I still need to do some testing on it to make sure it's compliant -- I was able to find a test sequence for the 64-bit variant but not for the 32-bit variant.