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save squiggle_more tweaks

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NunoSempere 2024-01-13 00:50:27 +01:00
parent eb1c592610
commit 3bb2804ccf
1 changed files with 21 additions and 4 deletions
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squiggle_more.c
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@ -60,13 +60,13 @@ void sampler_parallel(double (*sampler)(uint64_t* seed), double* results, int n_
} }
int i; int i;
#pragma omp parallel private(i, quotient) #pragma omp parallel private(i)
{ {
#pragma omp for #pragma omp for
for (i = 0; i < n_threads; i++) { for (i = 0; i < n_threads; i++) {
int quotient = n_samples / n_threads;
int lower_bound_inclusive = i * quotient; int lower_bound_inclusive = i * quotient;
int upper_bound_not_inclusive = ((i + 1) * quotient); // note the < in the for loop below, int upper_bound_not_inclusive = ((i + 1) * quotient); // note the < in the for loop below,
for (int j = lower_bound_inclusive; j < upper_bound_not_inclusive; j++) { for (int j = lower_bound_inclusive; j < upper_bound_not_inclusive; j++) {
results[j] = sampler(&(cache_box[i].seed)); results[j] = sampler(&(cache_box[i].seed));
// In principle, these results[j] could also result in two threads competing for the same cache line. // In principle, these results[j] could also result in two threads competing for the same cache line.
@ -75,6 +75,23 @@ void sampler_parallel(double (*sampler)(uint64_t* seed), double* results, int n_
// b) trying to unroll loops actually makes the code slower // b) trying to unroll loops actually makes the code slower
// c) 8 results[j] are 8 doubles, which fit a cache line. If n_samples/n_threads // c) 8 results[j] are 8 doubles, which fit a cache line. If n_samples/n_threads
} }
// Failed loop unrolling
/*
for (int j = lower_bound_inclusive; j < 4*(upper_bound_not_inclusive/4); j++) {
results[j+0] = sampler(&(cache_box[i].seed));
results[j+1] = sampler(&(cache_box[i].seed));
results[j+2] = sampler(&(cache_box[i].seed));
results[j+3] = sampler(&(cache_box[i].seed));
// In principle, these results[j] could also result in two threads competing for the same cache line.
// In practice, though,
// a) this would happen infrequently
// b) trying to unroll loops actually makes the code slower
// c) 8 results[j] are 8 doubles, which fit a cache line. If n_samples/n_threads
}
for (int j = 4*(upper_bound_not_inclusive/4); j < upper_bound_not_inclusive; j++) {
results[j] = sampler(&(cache_box[i].seed));
}
*/
} }
} }
for (int j = divisor_multiple; j < n_samples; j++) { for (int j = divisor_multiple; j < n_samples; j++) {
@ -92,7 +109,7 @@ typedef struct ci_t {
double high; double high;
} ci; } ci;
static void swp(int i, int j, double xs[]) inline static void swp(int i, int j, double xs[])
{ {
double tmp = xs[i]; double tmp = xs[i];
xs[i] = xs[j]; xs[i] = xs[j];