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Port per-ray RNG seeding and SPLIT randstate fix from McCode #2808 (fixes #392) #394

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Merged
g5t merged 1 commit into from
Oct 18, 2026
Merged

Port per-ray RNG seeding and SPLIT randstate fix from McCode #2808 (fixes #392) #394

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4 changes: 3 additions & 1 deletion src/mccode_antlr/translators/c_header.py
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Original file line number Diff line number Diff line change
Expand Up @@ -164,8 +164,10 @@ def jump_line(instance, jump):
#endif
#if RNG_ALG == _RNG_ALG_MT // MT
#define randstate_t uint32_t
#define RANDSTATE_LEN 1
#elif RNG_ALG == _RNG_ALG_KISS // KISS
#define randstate_t uint64_t
#define RANDSTATE_LEN 7
#endif

#ifndef MC_NUSERVAR
Expand All @@ -186,7 +188,7 @@ def jump_line(instance, jump):
double _mctmp_a; /* temp a */
double _mctmp_b; /* temp b */
double _mctmp_c; /* temp c */
randstate_t randstate[7];
randstate_t randstate[RANDSTATE_LEN];
double t, p; /* time, event weight */
long long _uid; /* Unique event ID */
long _index; /* component index where to send this event */
Expand Down
24 changes: 13 additions & 11 deletions src/mccode_antlr/translators/c_raytrace.py
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Original file line number Diff line number Diff line change
Expand Up @@ -52,9 +52,14 @@ def cogen_raytrace(source, ok_to_skip):
# following https://github.com/McStasMcXtrace/McCode/commit/72cb740d465e2780b228bd937cf62429a96f64d5
' #pragma acc loop independent',
f' for (int SplitN_{comp.name}=0; SplitN_{comp.name} < SplitS_{comp.name}; SplitN_{comp.name}++) {{',
' randstate_t randbackup = *_particle->randstate;',
' randstate_t randbackup[RANDSTATE_LEN];',
f' for (int Split_{comp.name}_randstate_idx = 0; Split_{comp.name}_randstate_idx < RANDSTATE_LEN; Split_{comp.name}_randstate_idx++) {{',
f' randbackup[Split_{comp.name}_randstate_idx] = _particle->randstate[Split_{comp.name}_randstate_idx];',
' }',
f' *_particle=Split_{comp.name}_particle;',
' *_particle->randstate = randbackup;',
f' for (int Split_{comp.name}_randstate_idx = 0; Split_{comp.name}_randstate_idx < RANDSTATE_LEN; Split_{comp.name}_randstate_idx++) {{',
f' _particle->randstate[Split_{comp.name}_randstate_idx] = randbackup[Split_{comp.name}_randstate_idx];',
' }',
f' p /= SplitS_{comp.name} > 0 ? SplitS_{comp.name} : 1;',
'#endif'
])
Expand Down Expand Up @@ -214,17 +219,16 @@ def cogen_raytrace(source, ok_to_skip):
" for (unsigned long pidx=0 ; pidx < gpu_innerloop ; pidx++) {",
" _class_particle particleN = mcgenstate(); // initial particle",
" _class_particle* _particle = &particleN;",
" particleN._uid = pidx;",
" particleN._uid = cloop*gpu_innerloop + pidx;",
" #ifdef USE_MPI",
" particleN._uid += mpi_node_rank * ncount;",
" particleN._uid += mpi_node_rank * loops*gpu_innerloop;",
" #endif",
"",
" srandom(_hash((pidx+1)*(seed+1)));",
" srandom(_hash(_hash(seed) + cloop*gpu_innerloop + pidx));",
" particle_uservar_init(_particle);",
"",
" raytrace(_particle);",
" } /* inner for */",
" seed = seed+gpu_innerloop;",
" } /* CPU for */",
" /* if on GPU, printf has been globally nullified, re-enable here */",
" #ifdef OPENACC",
Expand Down Expand Up @@ -318,11 +322,11 @@ def cogen_funnel(source, ok_to_skip):
" // generate particle state, set loop index and seed",
" particles[pidx] = mcgenstate();",
" _class_particle* _particle = particles + pidx;",
" _particle->_uid = pidx;",
" _particle->_uid = cloop*gpu_innerloop + pidx;",
" #ifdef USE_MPI",
" _particle->_uid += mpi_node_rank * ncount;",
" _particle->_uid += mpi_node_rank * loops*gpu_innerloop;",
" #endif",
" srandom(_hash((pidx+1)*(seed+1))); // _particle->state usage built into srandom macro",
" srandom(_hash(_hash(seed) + cloop*gpu_innerloop + pidx)); // _particle->state usage built into srandom macro",
" particle_uservar_init(_particle);",
" }",
"",
Expand Down Expand Up @@ -416,8 +420,6 @@ def cogen_funnel(source, ok_to_skip):

lines.extend([
' }',
" // jump to next viable seed",
" seed = seed + gpu_innerloop;",
" } // outer loop / particle batches",
"",
" free(particles);",
Expand Down
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