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 // Copyright 2017 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 import ( "math/big" "math/rand" "testing" ) var bigMaxUint64 = big.NewInt(0).SetUint64(maxUint64) func bigInt(xHi, xLo uint64) *big.Int { b := big.NewInt(0).SetUint64(xHi) b.Lsh(b, 64) b.Or(b, big.NewInt(0).SetUint64(xLo)) return b } func splitBigInt(b *big.Int) (outHi, outLo uint64) { outHi = big.NewInt(0).Rsh(b, 64).Uint64() outLo = big.NewInt(0).And(b, bigMaxUint64).Uint64() return } func bigMulMod128bits(xHi, xLo, yHi, yLo uint64) (outHi, outLo uint64) { bigX := bigInt(xHi, xLo) bigY := bigInt(yHi, yLo) return splitBigInt(bigX.Mul(bigX, bigY)) } func bigAddMod128bits(xHi, xLo, yHi, yLo uint64) (outHi, outLo uint64) { bigX := bigInt(xHi, xLo) bigY := bigInt(yHi, yLo) return splitBigInt(bigX.Add(bigX, bigY)) } type arithTest struct { xHi, xLo uint64 } const ( iLo = increment & maxUint64 iHi = (increment >> 64) & maxUint64 ) var arithTests = []arithTest{ {0, 0}, {0, 1}, {1, 0}, {0, maxUint64}, {maxUint64, 0}, {maxUint64, maxUint64}, // Randomly generated 64-bit integers. {3757956613005209672, 17983933746665545631}, {511324141977587414, 5626651684620191081}, {1534313104606153588, 2415006486399353367}, {6873586429837825902, 13854394671140464137}, {6617134480561088940, 18421520694158684312}, } func TestPCGAdd(t *testing.T) { for i, test := range arithTests { p := &PCGSource{ low: test.xLo, high: test.xHi, } p.add() expectHi, expectLo := bigAddMod128bits(test.xHi, test.xLo, iHi, iLo) if p.low != expectLo || p.high != expectHi { t.Errorf("%d: got hi=%d lo=%d; expect hi=%d lo=%d", i, p.high, p.low, expectHi, expectLo) } } } const ( mLo = multiplier & maxUint64 mHi = (multiplier >> 64) & maxUint64 ) func TestPCGMultiply(t *testing.T) { for i, test := range arithTests { p := &PCGSource{ low: test.xLo, high: test.xHi, } p.multiply() expectHi, expectLo := bigMulMod128bits(test.xHi, test.xLo, mHi, mLo) if p.low != expectLo || p.high != expectHi { t.Errorf("%d: got hi=%d lo=%d; expect hi=%d lo=%d", i, p.high, p.low, expectHi, expectLo) } } } func TestPCGMultiplyLong(t *testing.T) { if testing.Short() { return } for i := 0; i < 1e6; i++ { low := rand.Uint64() high := rand.Uint64() p := &PCGSource{ low: low, high: high, } p.multiply() expectHi, expectLo := bigMulMod128bits(high, low, mHi, mLo) if p.low != expectLo || p.high != expectHi { t.Fatalf("%d: (%d,%d): got hi=%d lo=%d; expect hi=%d lo=%d", i, high, low, p.high, p.low, expectHi, expectLo) } } } func BenchmarkPCGMultiply(b *testing.B) { low := rand.Uint64() high := rand.Uint64() p := &PCGSource{ low: low, high: high, } for i := 0; i < b.N; i++ { p.multiply() } }