| /******************************************************************************/ |
| #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. |
| * |
| * Macro parameters: |
| * uint32_t r : Result. |
| * unsigned lg_range : (0..32], number of least significant bits to return. |
| * uint32_t state : Seed value. |
| * const uint32_t a, c : See above discussion. |
| */ |
| #define prng32(r, lg_range, state, a, c) do { \ |
| assert((lg_range) > 0); \ |
| assert((lg_range) <= 32); \ |
| \ |
| r = (state * (a)) + (c); \ |
| state = r; \ |
| r >>= (32 - (lg_range)); \ |
| } while (false) |
| |
| /* Same as prng32(), but 64 bits of pseudo-randomness, using uint64_t. */ |
| #define prng64(r, lg_range, state, a, c) do { \ |
| assert((lg_range) > 0); \ |
| assert((lg_range) <= 64); \ |
| \ |
| r = (state * (a)) + (c); \ |
| state = r; \ |
| r >>= (64 - (lg_range)); \ |
| } while (false) |
| |
| #endif /* JEMALLOC_H_TYPES */ |
| /******************************************************************************/ |
| #ifdef JEMALLOC_H_STRUCTS |
| |
| #endif /* JEMALLOC_H_STRUCTS */ |
| /******************************************************************************/ |
| #ifdef JEMALLOC_H_EXTERNS |
| |
| #endif /* JEMALLOC_H_EXTERNS */ |
| /******************************************************************************/ |
| #ifdef JEMALLOC_H_INLINES |
| |
| #endif /* JEMALLOC_H_INLINES */ |
| /******************************************************************************/ |