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| author | Jason Evans <jasone@canonware.com> | 2012-05-12 00:48:33 (GMT) |
|---|---|---|
| committer | Jason Evans <jasone@canonware.com> | 2012-05-12 00:48:33 (GMT) |
| commit | fc9b1dbf69f59d7ecfc4ac68da9847e017e1d046 (patch) | |
| tree | 7f843c7c51cd5df5d3be1ca48f504325f0536c0d /include/jemalloc/internal/prng.h | |
| parent | fc1bb70e5f0d9a58b39efa39cc549b5af5104760 (diff) | |
| parent | cbb71caceb1e53d0fd21284ce298885327c211b4 (diff) | |
| download | jemalloc-3.0.0.zip jemalloc-3.0.0.tar.gz jemalloc-3.0.0.tar.bz2 | |
Merge branch 'dev'3.0.0
Conflicts:
ChangeLog
include/jemalloc/internal/chunk.h
src/chunk.c
src/huge.c
src/jemalloc.c
test/rallocm.c
Diffstat (limited to 'include/jemalloc/internal/prng.h')
| -rw-r--r-- | include/jemalloc/internal/prng.h | 60 |
1 files changed, 60 insertions, 0 deletions
diff --git a/include/jemalloc/internal/prng.h b/include/jemalloc/internal/prng.h new file mode 100644 index 0000000..83a5462 --- /dev/null +++ b/include/jemalloc/internal/prng.h @@ -0,0 +1,60 @@ +/******************************************************************************/ +#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 */ +/******************************************************************************/ |
