junrushao1994 commented on a change in pull request #8817:
URL: https://github.com/apache/tvm/pull/8817#discussion_r694983321
##########
File path: src/tir/schedule/concrete_schedule.cc
##########
@@ -208,6 +211,25 @@ Schedule ConcreteScheduleNode::Copy() const {
}
/******** Schedule: Schedule: Sampling ********/
+
+void ConcreteScheduleNode::Seed(support::LinearCongruentialEngine::TRandState
seed) {
+ support::LinearCongruentialEngine(&rand_state_).Seed(seed == -1 ?
std::random_device()() : seed);
+}
+support::LinearCongruentialEngine::TRandState ConcreteScheduleNode::ForkSeed()
{
+ // In order for reproducibility, we computer the new seed using RNG's random
state and a different
+ // set of parameters. Note that both 32767 and 1999999973 are prime numbers.
+ return (support::LinearCongruentialEngine(&rand_state_)() * 32767) %
1999999973;
+}
Review comment:
@tqchen I happened to implement a BSGS discrete logarithm this morning.
This is a simple but effective algorithm we use in high school competitive
programming:
https://gist.github.com/junrushao1994/d32f265f5b4815d4b346d6022e95f394.
I use this script to find out what the minimal number of trials is required
for a first repeat to happen given `num_threads` threads, and here is the
outcome when I set `num_threads=1000`.
```
k = 0, forked_seed = 1, repeat = 0
k = 1, forked_seed = 32767, repeat = 477805293
k = 2, forked_seed = 1073676289, repeat = 955610586
k = 3, forked_seed = 1151436593, repeat = 792763173
k = 4, forked_seed = 1123352159, repeat = 1465074278
k = 5, forked_seed = 880690861, repeat = 1324276493
k = 6, forked_seed = 1597831943, repeat = 1242547212
k = 7, forked_seed = 159983087, repeat = 1577951775
k = 8, forked_seed = 165882496, repeat = 12097717
k = 9, forked_seed = 1471819791, repeat = 670441922
k = 10, forked_seed = 1119742748, repeat = 130415288
k = 11, forked_seed = 611119031, repeat = 268696235
k = 12, forked_seed = 537559101, repeat = 53491731
k = 13, forked_seed = 199300256, repeat = 1422308282
k = 14, forked_seed = 471576507, repeat = 535435921
k = 15, forked_seed = 147613471, repeat = 482454183
k = 16, forked_seed = 850669543, repeat = 1171123831
k = 17, forked_seed = 1889291753, repeat = 1518153595
k = 18, forked_seed = 423706282, repeat = 325709943
k = 19, forked_seed = 1583929701, repeat = 1523336904
k = 20, forked_seed = 625213317, repeat = 2097645560
...
k = 990, forked_seed = 465632523, repeat = 1395274874
k = 991, forked_seed = 1381087097, repeat = 1524683345
k = 992, forked_seed = 81518328, repeat = 874365972
k = 993, forked_seed = 1111089621, repeat = 464689348
k = 994, forked_seed = 1074102788, repeat = 1779776079
k = 995, forked_seed = 1126529515, repeat = 113162479
k = 996, forked_seed = 993116317, repeat = 711897275
k = 997, forked_seed = 1442798429, repeat = 285912163
k = 998, forked_seed = 176761269, repeat = 918045815
k = 999, forked_seed = 1936579488, repeat = 43150205
min repeat: 1407035
```
In a word, in practice the repeat won't happen after 1407035 trials given
the `forked_seed` within 1000 threads.
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