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Yoshimi: found the bug

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plain flat off by one :-D
end pointer must be behind the last array element.
Thus we didn't use all state values, and thus our random numbers diverged
This commit is contained in:
Fischlurch 2018-12-31 09:50:53 +01:00
parent f0e482ad78
commit 5b8aef9623
1 changed files with 2 additions and 2 deletions
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4
research/try.cpp
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@ -161,7 +161,7 @@ class TrinomialPRNG
uint32_t val = *fptr += uint32_t(*rptr); uint32_t val = *fptr += uint32_t(*rptr);
uint32_t result = val >> 1; // Chucking least random bit. uint32_t result = val >> 1; // Chucking least random bit.
// Rationale: it has a less-then optimal repetition cycle. // Rationale: it has a less-then optimal repetition cycle.
int32_t *end = &state[62]; int32_t *end = &state[63];
++fptr; ++fptr;
if (fptr >= end) if (fptr >= end)
{ {
@ -199,7 +199,7 @@ main (int, char**)
StdlibPRNG oldGen; StdlibPRNG oldGen;
TrinomialPRNG newGen; TrinomialPRNG newGen;
for (uint64_t seed=0; seed <= UINT32_MAX; ++seed) for (uint64_t seed=INT32_MAX-100; seed <= UINT32_MAX; ++seed)
{ {
oldGen.init(seed); oldGen.init(seed);
newGen.init(seed); newGen.init(seed);