diff options
Diffstat (limited to '')
| -rw-r--r-- | src/math/rand/rng.go | 252 |
1 files changed, 252 insertions, 0 deletions
diff --git a/src/math/rand/rng.go b/src/math/rand/rng.go new file mode 100644 index 0000000..f305df1 --- /dev/null +++ b/src/math/rand/rng.go @@ -0,0 +1,252 @@ +// Copyright 2009 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package rand + +/* + * Uniform distribution + * + * algorithm by + * DP Mitchell and JA Reeds + */ + +const ( + rngLen = 607 + rngTap = 273 + rngMax = 1 << 63 + rngMask = rngMax - 1 + int32max = (1 << 31) - 1 +) + +var ( + // rngCooked used for seeding. See gen_cooked.go for details. + rngCooked [rngLen]int64 = [...]int64{ + -4181792142133755926, -4576982950128230565, 1395769623340756751, 5333664234075297259, + -6347679516498800754, 9033628115061424579, 7143218595135194537, 4812947590706362721, + 7937252194349799378, 5307299880338848416, 8209348851763925077, -7107630437535961764, + 4593015457530856296, 8140875735541888011, -5903942795589686782, -603556388664454774, + -7496297993371156308, 113108499721038619, 4569519971459345583, -4160538177779461077, + -6835753265595711384, -6507240692498089696, 6559392774825876886, 7650093201692370310, + 7684323884043752161, -8965504200858744418, -2629915517445760644, 271327514973697897, + -6433985589514657524, 1065192797246149621, 3344507881999356393, -4763574095074709175, + 7465081662728599889, 1014950805555097187, -4773931307508785033, -5742262670416273165, + 2418672789110888383, 5796562887576294778, 4484266064449540171, 3738982361971787048, + -4699774852342421385, 10530508058128498, 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= 0 + rng.feed = rngLen - rngTap + + seed = seed % int32max + if seed < 0 { + seed += int32max + } + if seed == 0 { + seed = 89482311 + } + + x := int32(seed) + for i := -20; i < rngLen; i++ { + x = seedrand(x) + if i >= 0 { + var u int64 + u = int64(x) << 40 + x = seedrand(x) + u ^= int64(x) << 20 + x = seedrand(x) + u ^= int64(x) + u ^= rngCooked[i] + rng.vec[i] = u + } + } +} + +// Int63 returns a non-negative pseudo-random 63-bit integer as an int64. +func (rng *rngSource) Int63() int64 { + return int64(rng.Uint64() & rngMask) +} + +// Uint64 returns a non-negative pseudo-random 64-bit integer as an uint64. +func (rng *rngSource) Uint64() uint64 { + rng.tap-- + if rng.tap < 0 { + rng.tap += rngLen + } + + rng.feed-- + if rng.feed < 0 { + rng.feed += rngLen + } + + x := rng.vec[rng.feed] + rng.vec[rng.tap] + rng.vec[rng.feed] = x + return uint64(x) +} |