From 0eaee4abb1d99f6165769a8ad2bfbf818860f40b Mon Sep 17 00:00:00 2001 From: Janne Blomqvist Date: Thu, 5 Sep 2019 09:59:55 +0300 Subject: [PATCH] Improve PRNG jumping when using threads Currently, when a new thread needs to use the RANDOM_NUMBER intrinsic, the per-thread PRNG state is initialized by copying the master state and then jumping forwards N*2**128 entries in the stream so that the PRNG streams for different threads don't alias each other, where N is the number of threads that have so far initialized the PRNG. With this patch the master state itself is jumped forwards once each time a new thread initializes the PRNG, thus obviating the need to jump through all the N-1 previous streams. Effectively turning an O(N) algorithm into an O(1) one. Regtested on x86_64-pc-linux-gnu. libgfortran/ChangeLog: 2019-09-05 Janne Blomqvist * intrinsics/random.c (master_init): Replace with master_state.init. (njumps): Remove variable. (master_state): Make instance of struct prng_state. (init_rand_state): When jumping, update the master_state once instead of keeping track of how many jumps need to be done. (SZU64): Modify to handle new master_state. (SZ): Likewise. (random_seed_i4): Likewise. (random_seed_i8): Likewise. From-SVN: r275397 --- libgfortran/ChangeLog | 13 ++++++++++ libgfortran/intrinsics/random.c | 46 ++++++++++++++------------------- 2 files changed, 32 insertions(+), 27 deletions(-) diff --git a/libgfortran/ChangeLog b/libgfortran/ChangeLog index 23a4c579351..8833c304967 100644 --- a/libgfortran/ChangeLog +++ b/libgfortran/ChangeLog @@ -1,3 +1,16 @@ +2019-09-05 Janne Blomqvist + + * intrinsics/random.c (master_init): Replace with + master_state.init. + (njumps): Remove variable. + (master_state): Make instance of struct prng_state. + (init_rand_state): When jumping, update the master_state once + instead of keeping track of how many jumps need to be done. + (SZU64): Modify to handle new master_state. + (SZ): Likewise. + (random_seed_i4): Likewise. + (random_seed_i8): Likewise. + 2019-08-17 Janne Blomqvist PR fortran/68401 diff --git a/libgfortran/intrinsics/random.c b/libgfortran/intrinsics/random.c index dd2c46e7ef5..bdad208bd98 100644 --- a/libgfortran/intrinsics/random.c +++ b/libgfortran/intrinsics/random.c @@ -194,13 +194,10 @@ typedef struct prng_state; -/* master_init, njumps, and master_state are the only variables - protected by random_lock. */ -static bool master_init; -static unsigned njumps; /* How many times we have jumped. */ -static uint64_t master_state[] = { - 0xad63fa1ed3b55f36ULL, 0xd94473e78978b497ULL, 0xbc60592a98172477ULL, - 0xa3de7c6e81265301ULL +/* master_state is the only variable protected by random_lock. */ +static prng_state master_state = { .init = false, .s = { + 0xad63fa1ed3b55f36ULL, 0xd94473e78978b497ULL, 0xbc60592a98172477ULL, + 0xa3de7c6e81265301ULL } }; @@ -353,24 +350,21 @@ init_rand_state (prng_state* rs, const bool locked) { if (!locked) __gthread_mutex_lock (&random_lock); - if (!master_init) + if (!master_state.init) { uint64_t os_seed; getosrandom (&os_seed, sizeof (os_seed)); - for (uint64_t i = 0; i < sizeof (master_state) / sizeof (uint64_t); i++) + for (uint64_t i = 0; i < sizeof (master_state.s) / sizeof (uint64_t); i++) { os_seed = splitmix64 (os_seed); - master_state[i] = os_seed; + master_state.s[i] = os_seed; } - njumps = 0; - master_init = true; + master_state.init = true; } - memcpy (&rs->s, master_state, sizeof (master_state)); - unsigned n = njumps++; + memcpy (&rs->s, master_state.s, sizeof (master_state.s)); + jump (&master_state); if (!locked) __gthread_mutex_unlock (&random_lock); - for (unsigned i = 0; i < n; i++) - jump (rs); rs->init = true; } @@ -727,7 +721,7 @@ arandom_r16 (gfc_array_r16 *x) /* Number of elements in master_state array. */ -#define SZU64 (sizeof (master_state) / sizeof (uint64_t)) +#define SZU64 (sizeof (master_state.s) / sizeof (uint64_t)) /* Keys for scrambling the seed in order to avoid poor seeds. */ @@ -757,7 +751,7 @@ void random_seed_i4 (GFC_INTEGER_4 *size, gfc_array_i4 *put, gfc_array_i4 *get) { uint64_t seed[SZU64]; -#define SZ (sizeof (master_state) / sizeof (GFC_INTEGER_4)) +#define SZ (sizeof (master_state.s) / sizeof (GFC_INTEGER_4)) /* Check that we only have one argument present. */ if ((size ? 1 : 0) + (put ? 1 : 0) + (get ? 1 : 0) > 1) @@ -800,7 +794,7 @@ random_seed_i4 (GFC_INTEGER_4 *size, gfc_array_i4 *put, gfc_array_i4 *get) a processor-dependent value to the seed." */ if (size == NULL && put == NULL && get == NULL) { - master_init = false; + master_state.init = false; init_rand_state (rs, true); } @@ -822,9 +816,8 @@ random_seed_i4 (GFC_INTEGER_4 *size, gfc_array_i4 *put, gfc_array_i4 *get) /* We put it after scrambling the bytes, to paper around users who provide seeds with quality only in the lower or upper part. */ - scramble_seed (master_state, seed); - njumps = 0; - master_init = true; + scramble_seed (master_state.s, seed); + master_state.init = true; init_rand_state (rs, true); } @@ -844,7 +837,7 @@ random_seed_i8 (GFC_INTEGER_8 *size, gfc_array_i8 *put, gfc_array_i8 *get) if ((size ? 1 : 0) + (put ? 1 : 0) + (get ? 1 : 0) > 1) runtime_error ("RANDOM_SEED should have at most one argument present."); -#define SZ (sizeof (master_state) / sizeof (GFC_INTEGER_8)) +#define SZ (sizeof (master_state.s) / sizeof (GFC_INTEGER_8)) if (size != NULL) *size = SZ; @@ -881,7 +874,7 @@ random_seed_i8 (GFC_INTEGER_8 *size, gfc_array_i8 *put, gfc_array_i8 *get) a processor-dependent value to the seed." */ if (size == NULL && put == NULL && get == NULL) { - master_init = false; + master_state.init = false; init_rand_state (rs, true); } @@ -900,9 +893,8 @@ random_seed_i8 (GFC_INTEGER_8 *size, gfc_array_i8 *put, gfc_array_i8 *get) memcpy (&seed[i], &(put->base_addr[i * GFC_DESCRIPTOR_STRIDE(put,0)]), sizeof (GFC_UINTEGER_8)); - scramble_seed (master_state, seed); - njumps = 0; - master_init = true; + scramble_seed (master_state.s, seed); + master_state.init = true; init_rand_state (rs, true); } -- 2.30.2