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https://github.com/shopspring/decimal.git
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refactoring div test. benchmarks for old Div vs. New Div
This commit is contained in:
Roland Averkamp
parent
696232de64
commit
5c1d2008f5
1 changed files with 130 additions and 34 deletions
164
decimal_test.go
164
decimal_test.go
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@ -4,6 +4,7 @@ import (
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"encoding/json"
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"encoding/xml"
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"math"
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"math/big"
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"strconv"
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"strings"
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"testing"
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@ -742,46 +743,29 @@ func TestDecimal_QuoRem(t *testing.T) {
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}
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}
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func TestDecimal_QuoRem2(t *testing.T) {
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type DivTestCase struct {
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d Decimal
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d2 Decimal
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prec int32
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}
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func createDivTestCases() []DivTestCase {
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res := make([]DivTestCase, 0)
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var n int32 = 5
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a := []int{1, 2, 3, 6, 7, 10, 100, 14, 5, 400, 0}
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for s := -1; s < 2; s = s + 2 {
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for s2 := -1; s2 < 2; s2 = s2 + 2 {
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for e1 := -n; e1 < n; e1++ {
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for e2 := -n; e2 < n; e2++ {
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a := []int{1, 2, 3, 6, 7, 10, 100, 14, 5, 400, 0, 1000000, 1000000 + 1, 1000000 - 1}
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for s := -1; s < 2; s = s + 2 { // 2
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for s2 := -1; s2 < 2; s2 = s2 + 2 { // 2
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for e1 := -n; e1 <= n; e1++ { // 2n+1
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for e2 := -n; e2 <= n; e2++ { // 2n+1
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var prec int32
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for prec = -n; prec < n; prec++ {
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for _, v1 := range a {
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for _, v2 := range a {
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if v2 == 0 {
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continue
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}
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for prec = -n; prec <= n; prec++ { // 2n+1
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for _, v1 := range a { // 11
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for _, v2 := range a { // 11, even if 0 is skipped
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sign1 := New(int64(s), 0)
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sign2 := New(int64(s2), 0)
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d := sign1.Mul(New(int64(v1), int32(e1)))
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d2 := sign2.Mul(New(int64(v2), int32(e2)))
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q, r := d.QuoRem(d2, prec)
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// rule 1: d = d2*q +r
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if !d.Equals(d2.Mul(q).Add(r)) {
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t.Errorf("not fitting, d=%v, d2=%v, prec=%d, q=%v, r=%v",
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d, d2, prec, q, r)
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}
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// rule 2: q is integral multiple of 10^(-prec)
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if !q.Equals(q.Truncate(prec)) {
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t.Errorf("quotient wrong precision, d=%v, d2=%v, prec=%d, q=%v, r=%v",
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d, d2, prec, q, r)
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}
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// rule 3: abs(r)<abs(d) * 10^(-prec)
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if r.Abs().Cmp(d2.Abs().Mul(New(1, -prec))) >= 0 {
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t.Errorf("remainder too large, d=%v, d2=%v, prec=%d, q=%v, r=%v",
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d, d2, prec, q, r)
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}
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// rule 4: r and d have the same sign
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if r.value.Sign()*d.value.Sign() < 0 {
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t.Errorf("signum of divisor and rest do not match, "+
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"d=%v, d2=%v, prec=%d, q=%v, r=%v",
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d, d2, prec, q, r)
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}
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res = append(res, DivTestCase{d, d2, prec})
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}
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}
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}
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@ -789,6 +773,96 @@ func TestDecimal_QuoRem2(t *testing.T) {
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}
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}
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}
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return res
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}
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func TestDecimal_QuoRem2(t *testing.T) {
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for _, tc := range createDivTestCases() {
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d := tc.d
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if sign(tc.d2) == 0 {
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continue
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}
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d2 := tc.d2
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prec := tc.prec
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q, r := d.QuoRem(d2, prec)
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// rule 1: d = d2*q +r
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if !d.Equals(d2.Mul(q).Add(r)) {
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t.Errorf("not fitting, d=%v, d2=%v, prec=%d, q=%v, r=%v",
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d, d2, prec, q, r)
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}
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// rule 2: q is integral multiple of 10^(-prec)
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if !q.Equals(q.Truncate(prec)) {
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t.Errorf("quotient wrong precision, d=%v, d2=%v, prec=%d, q=%v, r=%v",
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d, d2, prec, q, r)
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}
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// rule 3: abs(r)<abs(d) * 10^(-prec)
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if r.Abs().Cmp(d2.Abs().Mul(New(1, -prec))) >= 0 {
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t.Errorf("remainder too large, d=%v, d2=%v, prec=%d, q=%v, r=%v",
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d, d2, prec, q, r)
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}
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// rule 4: r and d have the same sign
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if r.value.Sign()*d.value.Sign() < 0 {
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t.Errorf("signum of divisor and rest do not match, "+
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"d=%v, d2=%v, prec=%d, q=%v, r=%v",
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d, d2, prec, q, r)
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}
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}
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}
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// this is the old Div method from decimal
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// Div returns d / d2. If it doesn't divide exactly, the result will have
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// DivisionPrecision digits after the decimal point.
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func (d Decimal) DivOld(d2 Decimal, prec int) Decimal {
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// NOTE(vadim): division is hard, use Rat to do it
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ratNum := d.Rat()
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ratDenom := d2.Rat()
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quoRat := big.NewRat(0, 1).Quo(ratNum, ratDenom)
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// HACK(vadim): converting from Rat to Decimal inefficiently for now
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ret, err := NewFromString(quoRat.FloatString(prec))
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if err != nil {
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panic(err) // this should never happen
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}
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return ret
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}
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func Benchmark_DivideOriginal(b *testing.B) {
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tcs := createDivTestCases()
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b.ResetTimer()
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for i := 0; i < b.N; i++ {
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for _, tc := range tcs {
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d := tc.d
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if sign(tc.d2) == 0 {
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continue
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}
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d2 := tc.d2
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prec := tc.prec
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a := d.DivOld(d2, int(prec))
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if sign(a) > 2 {
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panic("dummy panic")
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}
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}
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}
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}
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func Benchmark_DivideNew(b *testing.B) {
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tcs := createDivTestCases()
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b.ResetTimer()
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for i := 0; i < b.N; i++ {
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for _, tc := range tcs {
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d := tc.d
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if sign(tc.d2) == 0 {
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continue
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}
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d2 := tc.d2
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prec := tc.prec
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a := d.DivRound(d2, prec)
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if sign(a) > 2 {
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panic("dummy panic")
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}
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}
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}
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}
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func sign(d Decimal) int {
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@ -845,6 +919,28 @@ func TestDecimal_DivRound(t *testing.T) {
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}
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}
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func TestDecimal_DivRound2(t *testing.T) {
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for _, tc := range createDivTestCases() {
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d := tc.d
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if sign(tc.d2) == 0 {
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continue
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}
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d2 := tc.d2
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prec := tc.prec
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q := d.DivRound(d2, prec)
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if sign(q)*sign(d)*sign(d2) < 0 {
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t.Errorf("sign of quotient wrong, got: %v/%v is about %v", d, d2, q)
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}
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x := q.Mul(d2).Abs().Sub(d.Abs()).Mul(New(2, 0))
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if x.Cmp(d2.Abs().Mul(New(1, -prec))) > 0 {
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t.Errorf("wrong rounding, got: %v/%v prec=%d is about %v", d, d2, prec, q)
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}
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if x.Cmp(d2.Abs().Mul(New(-1, -prec))) <= 0 {
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t.Errorf("wrong rounding, got: %v/%v prec=%d is about %v", d, d2, prec, q)
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}
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}
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}
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func TestDecimal_Overflow(t *testing.T) {
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if !didPanic(func() { New(1, math.MinInt32).Mul(New(1, math.MinInt32)) }) {
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t.Fatalf("should have gotten an overflow panic")
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