// 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, -589538253572429690, 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-6344160503358350167, 5896236396443472108, -758328221503023383, -1894351639983151068, -307900319840287220, -6278469401177312761, -2171292963361310674, 8382142935188824023, 9103922860780351547, 4152330101494654406, } ) type rngSource struct { tap int // index into vec feed int // index into vec vec [rngLen]int64 // current feedback register } // seed rng x[n+1] = 48271 * x[n] mod (2**31 - 1) func seedrand(x int32) int32 { const ( A = 48271 Q = 44488 R = 3399 ) hi := x / Q lo := x % Q x = A*lo - R*hi if x < 0 { x += int32max } return x } // Seed uses the provided seed value to initialize the generator to a deterministic state. func (rng *rngSource) Seed(seed int64) { rng.tap = 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 a 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) }