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RNG seed change safer for large volumes; this is a long term solution

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This commit is contained in:
Peter Boyle
2024-02-07 00:56:39 +00:00
parent 91cf5ee312
commit 7019916294
4 changed files with 12 additions and 150 deletions
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10
Grid/lattice/Lattice_rng.h
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@ -152,6 +152,7 @@ public:
#ifdef RNG_FAST_DISCARD
static void Skip(RngEngine &eng,uint64_t site)
{
#if 0
/////////////////////////////////////////////////////////////////////////////////////
// Skip by 2^40 elements between successive lattice sites
// This goes by 10^12.
@ -162,9 +163,9 @@ public:
// tens of seconds per trajectory so this is clean in all reasonable cases,
// and margin of safety is orders of magnitude.
// We could hack Sitmo to skip in the higher order words of state if necessary
//
// Replace with 2^30 ; avoid problem on large volumes
//
//
// Replace with 2^30 ; avoid problem on large volumes
//
/////////////////////////////////////////////////////////////////////////////////////
// uint64_t skip = site+1; // Old init Skipped then drew. Checked compat with faster init
const int shift = 30;
@ -179,6 +180,9 @@ public:
assert((skip >> shift)==site); // check for overflow
eng.discard(skip);
#else
eng.discardhi(site);
#endif
// std::cout << " Engine " <<site << " state " <<eng<<std::endl;
}
#endif

6
Grid/sitmo_rng/sitmo_prng_engine.hpp
View File

@ -218,6 +218,10 @@ public:
// -------------------------------------------------
// misc
// -------------------------------------------------
void discardhi(uint64_t z) {
_s[3] += z;
encrypt_counter();
}
// req: 26.5.1.4 Random number engine requirements, p.908 table 117, row 9
// Advances e’s state ei to ei+z by any means equivalent to z
@ -387,4 +391,4 @@ private:
#undef MIXK
#undef MIX2
#endif
#endif