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util_test.go
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util_test.go
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// Copyright 2012, Kevin Ko <kevin@faveset.com>. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package rabin
import (
"testing"
)
import (
Crand "crypto/rand"
"fmt"
"math"
"math/big"
"math/rand"
)
func Test_CalcPrimes(t *testing.T) {
cmp := func(a, b []int) bool {
if len(a) != len(b) {
return false
}
for ii, v := range a {
if v != b[ii] {
return false
}
}
return true
}
if !cmp(CalcPrimes(2), []int{2}) {
t.Error("2")
}
if !cmp(CalcPrimes(11), []int{2, 3, 5, 7, 11}) {
t.Error("11")
}
}
func Test_IsPowerOfTwo(t *testing.T) {
if !IsPowerOfTwo(2) {
t.Error("2")
}
if IsPowerOfTwo(3) {
t.Error("3")
}
if !IsPowerOfTwo(4) {
t.Error("4")
}
if IsPowerOfTwo(5) {
t.Error("5")
}
}
func Test_MakeRandom(t *testing.T) {
// Seed the source with a strongly random seed (crypto/rand).
maxSeed := big.NewInt(math.MaxInt64)
seed, err := Crand.Int(Crand.Reader, maxSeed)
if err != nil {
panic(err)
}
source := rand.NewSource(seed.Int64())
randGen := rand.New(source)
// This is a crude test. There are 2^60 possible degree 61 polynomials.
// The probability that we draw 5 identical ones in sequence
// uniformly at random is (1/2^60)^4 = 1/2^64, which should never
// happen.
degree := 61
p := MakeRandom(randGen, degree)
if p.degree != 61 {
t.Error("wrong degree")
}
numDuplicates := 0
for ii := 0; ii < 4; ii++ {
cmp := MakeRandom(randGen, degree)
if p.Cmp(cmp) == 0 {
numDuplicates++
}
}
if numDuplicates >= 4 {
t.Error("improbable match")
}
}
func Test_FindIrreducible(t *testing.T) {
// NOTE: this is very crude.
p := FindIrreducible(32)
if p.degree != 32 {
t.Error("p.degree != 32")
}
if !p.Irreducible() {
t.Error("p not irreducible")
}
p = FindIrreducible(64)
if !p.Irreducible() {
t.Error("p not irreducible")
}
}
func Test_IrreducibleUint64(t *testing.T) {
p := FindIrreducible(64)
deg, coeffs := p.Uint64()
cmp := NewPolynomialFromUint64(deg, coeffs)
if p.Cmp(cmp) != 0 {
t.Error("equality failed")
}
}
func Test_PowerTable(t *testing.T) {
p := NewPolynomialFromUint64(kIrreduciblePolyDegree, kIrreduciblePolyCoeffs)
// Offset by a little bit to test forwarding.
pt := makePowerTable(70)
for ii := 0; ii < len(pt); ii++ {
coeffs := new(big.Int)
coeffs.SetBit(coeffs, 70+ii, 1)
powerPoly := NewPolynomialFromBigInt(coeffs)
powerPoly.Mod(powerPoly, p)
_, cmpCoeffs := powerPoly.Uint64()
if cmpCoeffs != pt[ii] {
t.Error(fmt.Sprintf("mismatch term %d (0x%x, 0x%x)",
ii, cmpCoeffs, pt[ii]))
}
}
}
func Test_MakeTables32(t *testing.T) {
p := NewPolynomialFromUint64(kIrreduciblePolyDegree, kIrreduciblePolyCoeffs)
cmp := MakeRabinTables32FromPoly(p)
tables := makeRabinTables32Raw()
for ii := 0; ii < 4; ii++ {
for jj := 0; jj < 256; jj++ {
vCmp := cmp[ii][jj]
v := tables[ii][jj]
if vCmp != v {
t.Error(fmt.Sprintf("[%d][%d]: 0x%x != 0x%x", ii, jj, v, vCmp))
}
}
}
}
func Test_RabinRollingTables32(t *testing.T) {
p := NewPolynomialFromUint64(kIrreduciblePolyDegree, kIrreduciblePolyCoeffs)
checkCoeffs := func(cmp uint64, power int, b byte) {
coeffs := big.NewInt(int64(b))
coeffs.Lsh(coeffs, uint(power))
powerPoly := NewPolynomialFromBigInt(coeffs)
powerPoly.Mod(powerPoly, p)
_, cmpCoeffs := powerPoly.Uint64()
if cmpCoeffs != cmp {
t.Error(fmt.Sprintf("mismatch term (0x%x, 0x%x)",
cmpCoeffs, cmp))
}
}
basePower := 128 * 8
tables := makeRabinRollingTables32(128)
for ii := 0; ii < 256; ii++ {
checkCoeffs(tables.t8m0[ii], basePower, byte(ii))
checkCoeffs(tables.t8m8[ii], basePower+8, byte(ii))
checkCoeffs(tables.t8m16[ii], basePower+16, byte(ii))
checkCoeffs(tables.t8m24[ii], basePower+24, byte(ii))
}
}
func Test_MakeTables64(t *testing.T) {
p := NewPolynomialFromUint64(kIrreduciblePolyDegree, kIrreduciblePolyCoeffs)
cmp := MakeRabinTables64FromPoly(p)
tables := makeRabinTables64Raw()
for ii := 0; ii < 8; ii++ {
for jj := 0; jj < 256; jj++ {
vCmp := cmp[ii][jj]
v := tables[ii][jj]
if vCmp != v {
t.Error(fmt.Sprintf("[%d][%d]: 0x%x != 0x%x", ii, jj, v, vCmp))
}
}
}
}
func Benchmark_MakeTables32(b *testing.B) {
for ii := 0; ii < b.N; ii++ {
makeRabinTables32()
}
}
func Benchmark_MakeTables32Naive(b *testing.B) {
p := NewPolynomialFromUint64(kIrreduciblePolyDegree, kIrreduciblePolyCoeffs)
for ii := 0; ii < b.N; ii++ {
MakeRabinTables32FromPoly(p)
}
}