| /******************************************************************************/ |
| #ifdef JEMALLOC_H_TYPES |
| |
| /* |
| * Simple linear congruential pseudo-random number generator: |
| * |
| * prng(y) = (a*x + c) % m |
| * |
| * where the following constants ensure maximal period: |
| * |
| * a == Odd number (relatively prime to 2^n), and (a-1) is a multiple of 4. |
| * c == Odd number (relatively prime to 2^n). |
| * m == 2^32 |
| * |
| * See Knuth's TAOCP 3rd Ed., Vol. 2, pg. 17 for details on these constraints. |
| * |
| * This choice of m has the disadvantage that the quality of the bits is |
| * proportional to bit position. For example, the lowest bit has a cycle of 2, |
| * the next has a cycle of 4, etc. For this reason, we prefer to use the upper |
| * bits. |
| */ |
| |
| #define PRNG_A_32 UINT32_C(1103515241) |
| #define PRNG_C_32 UINT32_C(12347) |
| |
| #define PRNG_A_64 UINT64_C(6364136223846793005) |
| #define PRNG_C_64 UINT64_C(1442695040888963407) |
| |
| #endif /* JEMALLOC_H_TYPES */ |
| /******************************************************************************/ |
| #ifdef JEMALLOC_H_STRUCTS |
| |
| #endif /* JEMALLOC_H_STRUCTS */ |
| /******************************************************************************/ |
| #ifdef JEMALLOC_H_EXTERNS |
| |
| #endif /* JEMALLOC_H_EXTERNS */ |
| /******************************************************************************/ |
| #ifdef JEMALLOC_H_INLINES |
| |
| #ifndef JEMALLOC_ENABLE_INLINE |
| uint32_t prng_state_next_u32(uint32_t state); |
| uint64_t prng_state_next_u64(uint64_t state); |
| size_t prng_state_next_zu(size_t state); |
| |
| uint32_t prng_lg_range_u32(uint32_t *state, unsigned lg_range, |
| bool atomic); |
| uint64_t prng_lg_range_u64(uint64_t *state, unsigned lg_range); |
| size_t prng_lg_range_zu(size_t *state, unsigned lg_range, bool atomic); |
| |
| uint32_t prng_range_u32(uint32_t *state, uint32_t range, bool atomic); |
| uint64_t prng_range_u64(uint64_t *state, uint64_t range); |
| size_t prng_range_zu(size_t *state, size_t range, bool atomic); |
| #endif |
| |
| #if (defined(JEMALLOC_ENABLE_INLINE) || defined(JEMALLOC_PRNG_C_)) |
| JEMALLOC_ALWAYS_INLINE uint32_t |
| prng_state_next_u32(uint32_t state) |
| { |
| |
| return ((state * PRNG_A_32) + PRNG_C_32); |
| } |
| |
| JEMALLOC_ALWAYS_INLINE uint64_t |
| prng_state_next_u64(uint64_t state) |
| { |
| |
| return ((state * PRNG_A_64) + PRNG_C_64); |
| } |
| |
| JEMALLOC_ALWAYS_INLINE size_t |
| prng_state_next_zu(size_t state) |
| { |
| |
| #if LG_SIZEOF_PTR == 2 |
| return ((state * PRNG_A_32) + PRNG_C_32); |
| #elif LG_SIZEOF_PTR == 3 |
| return ((state * PRNG_A_64) + PRNG_C_64); |
| #else |
| #error Unsupported pointer size |
| #endif |
| } |
| |
| JEMALLOC_ALWAYS_INLINE uint32_t |
| prng_lg_range_u32(uint32_t *state, unsigned lg_range, bool atomic) |
| { |
| uint32_t ret, state1; |
| |
| assert(lg_range > 0); |
| assert(lg_range <= 32); |
| |
| if (atomic) { |
| uint32_t state0; |
| |
| do { |
| state0 = atomic_read_u32(state); |
| state1 = prng_state_next_u32(state0); |
| } while (atomic_cas_u32(state, state0, state1)); |
| } else { |
| state1 = prng_state_next_u32(*state); |
| *state = state1; |
| } |
| ret = state1 >> (32 - lg_range); |
| |
| return (ret); |
| } |
| |
| /* 64-bit atomic operations cannot be supported on all relevant platforms. */ |
| JEMALLOC_ALWAYS_INLINE uint64_t |
| prng_lg_range_u64(uint64_t *state, unsigned lg_range) |
| { |
| uint64_t ret, state1; |
| |
| assert(lg_range > 0); |
| assert(lg_range <= 64); |
| |
| state1 = prng_state_next_u64(*state); |
| *state = state1; |
| ret = state1 >> (64 - lg_range); |
| |
| return (ret); |
| } |
| |
| JEMALLOC_ALWAYS_INLINE size_t |
| prng_lg_range_zu(size_t *state, unsigned lg_range, bool atomic) |
| { |
| size_t ret, state1; |
| |
| assert(lg_range > 0); |
| assert(lg_range <= ZU(1) << (3 + LG_SIZEOF_PTR)); |
| |
| if (atomic) { |
| size_t state0; |
| |
| do { |
| state0 = atomic_read_zu(state); |
| state1 = prng_state_next_zu(state0); |
| } while (atomic_cas_zu(state, state0, state1)); |
| } else { |
| state1 = prng_state_next_zu(*state); |
| *state = state1; |
| } |
| ret = state1 >> ((ZU(1) << (3 + LG_SIZEOF_PTR)) - lg_range); |
| |
| return (ret); |
| } |
| |
| JEMALLOC_ALWAYS_INLINE uint32_t |
| prng_range_u32(uint32_t *state, uint32_t range, bool atomic) |
| { |
| uint32_t ret; |
| unsigned lg_range; |
| |
| assert(range > 1); |
| |
| /* Compute the ceiling of lg(range). */ |
| lg_range = ffs_u32(pow2_ceil_u32(range)) - 1; |
| |
| /* Generate a result in [0..range) via repeated trial. */ |
| do { |
| ret = prng_lg_range_u32(state, lg_range, atomic); |
| } while (ret >= range); |
| |
| return (ret); |
| } |
| |
| JEMALLOC_ALWAYS_INLINE uint64_t |
| prng_range_u64(uint64_t *state, uint64_t range) |
| { |
| uint64_t ret; |
| unsigned lg_range; |
| |
| assert(range > 1); |
| |
| /* Compute the ceiling of lg(range). */ |
| lg_range = ffs_u64(pow2_ceil_u64(range)) - 1; |
| |
| /* Generate a result in [0..range) via repeated trial. */ |
| do { |
| ret = prng_lg_range_u64(state, lg_range); |
| } while (ret >= range); |
| |
| return (ret); |
| } |
| |
| JEMALLOC_ALWAYS_INLINE size_t |
| prng_range_zu(size_t *state, size_t range, bool atomic) |
| { |
| size_t ret; |
| unsigned lg_range; |
| |
| assert(range > 1); |
| |
| /* Compute the ceiling of lg(range). */ |
| lg_range = ffs_u64(pow2_ceil_u64(range)) - 1; |
| |
| /* Generate a result in [0..range) via repeated trial. */ |
| do { |
| ret = prng_lg_range_zu(state, lg_range, atomic); |
| } while (ret >= range); |
| |
| return (ret); |
| } |
| #endif |
| |
| #endif /* JEMALLOC_H_INLINES */ |
| /******************************************************************************/ |