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Allow 1 ULP of error in exp, ln, log10 and power GDA tests #152

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Allow 1 ULP of error in exp, ln, log10 and power GDA tests #152

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e65a659
Allow 1 ULP of error in GDA tests
rdingwall May 23, 2020
9ed91b6
Merge branch 'master' into gda_dectest_allow_1ulp_error
rdingwall Aug 7, 2021
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50 changes: 42 additions & 8 deletions dectest/test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@ import (
"os"
"reflect"
"strconv"
"strings"
"testing"

"github.com/ericlagergren/decimal"
Expand Down Expand Up @@ -277,15 +278,15 @@ got : %v
func check(t *testing.T, z, r *decimal.Big, c *Case, flags decimal.Condition) {
helper(t)()
if !equal(z, r) {
str := fmt.Sprintf(`%s
wanted: %q (%s:%d)
got : %q (%s:%d)
`,
s := []string{
c.ShortString(10000),
r, flags, -r.Scale(),
z, z.Context.Conditions, -z.Scale(),
)
t.Log(str)
fmt.Sprintf("wanted: %q (%s:%d)", r, flags, -r.Scale()),
fmt.Sprintf("got : %q (%s:%d)", z, z.Context.Conditions, -z.Scale()),
}
if isInexact(z) && allow1ULPError[c.Op] && equalWithin1ULP(z, r) {
s = append(s, "passed within 1 ULP")
}
t.Log(strings.Join(s, "\n"), "\n")
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I refactored this string builder from one fmt.Sprintf() into strings.Join() to preserve test output (but have the ability to insert the optional ULP line in the middle)

}
}

Expand Down Expand Up @@ -321,6 +322,35 @@ func equal(x, y *decimal.Big) bool {
return cmp && scl && prec
}

func equalWithin1ULP(x, y *decimal.Big) bool {
if !x.IsFinite() || !y.IsFinite() {
return false
}
formX, negX, coeffX, expX := x.Decompose(make([]byte, 2<<3))
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Off hand (I haven’t tested it yet, or had my coffee :-), I’m not sure if this is accurate. [123, -2] and [1234, -3] should compare equal within 1 ULP, but would fail here since their exponents differ.

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@ericlagergren ericlagergren Aug 7, 2021 •
edited
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Hey @rdingwall, apparently I had added this comment (one year ago!) but never actually clicked “submit” on the review. Sorry for that. I only noticed when I got the email that you’d rebased!

formY, negY, coeffY, expY := y.Decompose(make([]byte, 2<<3))
if formX != formY || negX != negY || expX != expY {
return false
}
l := len(coeffX)
if len(coeffY) != l {
return false
}
for i := 0; i < l-1; i++ {
if coeffX[i] != coeffY[i] {
return false
}
}
d := coeffX[l-1] - coeffY[l-1]
return d == 0x01 || d == 0xff
}

var allow1ULPError = map[Op]bool{
Exp: true,
Ln: true,
Log10: true,
Power: true,
}

// helper returns testing.T.Helper, if it exists.
func helper(v interface{}) func() {
if fn, ok := v.(interface {
Expand All @@ -345,3 +375,7 @@ func convertConditions(c Condition) (decimal.Condition, bool) {
}
return r, true
}

func isInexact(x *decimal.Big) bool {
return x.Context.Conditions&decimal.Inexact == decimal.Inexact
}