[Bug libstdc++/89979] subtract_with_carry_engine incorrect carry flag
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89979 --- Comment #4 from Christoph Conrads --- > LLVM's libc++ does not go into the 0 loop but still does not do a good job: The subtract-with-carry PRNG is a simple PRNG, it has a very long period whose length can be proved with elementary number theory but the randomness properties of an SWC on its own are bad which is why you have to discard a lot of values. For reference, std::ranlux48 uses about 11 out of 389 values and you can detect (self-advertisement: it discards much less variates if you you use my parameters: b=32, s=2, r=13, see https://github.com/boostorg/random/issues/57). Here are the random values are drawing 100 times: 114294 141465 4294632814 252684 106646 4294497449 475286 Here are the random values after drawing 1000 times: 3844519667 4029384828 773557245 3005408692 1891078342 2314767096 2602358454 After drawing 2000 times: 671901017 3735908022 2276383719 2942324048 2197640583 3544339665 2823890385
[Bug libstdc++/89979] subtract_with_carry_engine incorrect carry flag
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89979 --- Comment #3 from Andrew Pinski --- LLVM's libc++ does not go into the 0 loop but still does not do a good job: 4294967295 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 4294967295 1 0 0 0 0 0 4294967295 4294967295 1 0 0 0 0 4294967295 4294967295 4294967295 1 0 0 0 4294967295 4294967295 4294967295 4294967294 0 0 0 4294967295 4294967295 4294967295 4294967294 4294967295 0 0 4294967295 4294967295 4294967295 4294967294 4294967295 4294967295 0 4294967295 4294967295 4294967295 4294967294 4294967295 4294967295 4294967294 0 4294967295 4294967295 4294967294 4294967295 4294967295 4294967294 0 0 4294967295 4294967294 4294967295 4294967295 4294967294 0 0 0 4294967294 4294967295 4294967295 4294967294 0 0 4294967295 1 While libstdc++ does seems to get into a loop: 4294967295 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 2 0 0 0 0 0 0 0 0 3 0 0 0 0 0 0 0 0 4 0 0 0 0 0 0 0 0 5 0 0 0 0 0 0 0 0 6 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 2 0 0 0 0 0 0 0 0 3 0 0 0 0 0 0 0 0 4
[Bug libstdc++/89979] subtract_with_carry_engine incorrect carry flag
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89979 Jonathan Wakely changed: What|Removed |Added Status|UNCONFIRMED |NEW Last reconfirmed||2019-04-05 Ever confirmed|0 |1 --- Comment #2 from Jonathan Wakely --- (In reply to Christoph Conrads from comment #1) > There is no attachment with the preprocessed code demonstrating the problem > because the this code is 1.2 MB large. That's OK in this case as you code doesn't depend on anything except standard library headers.
[Bug libstdc++/89979] subtract_with_carry_engine incorrect carry flag
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89979 --- Comment #1 from Christoph Conrads --- There is no attachment with the preprocessed code demonstrating the problem because the this code is 1.2 MB large.
