func TestPowIntegers(t *testing.T) {
for _, test := range []struct {
z, w string
want string
}{
{"2", "5", "32"},
{"2", "10", "1024"},
{"2", "64", "18446744073709551616"},
{"2", "-5", "0.03125"},
{"2", "-10", "0.0009765625"},
{"2", "-64", "5.42101086242752217003726400434970855712890625e-20"},
{"1.5", "8", "25.62890625"},
} {
for _, prec := range []uint{24, 53, 64, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000} {
want := new(big.Float).SetPrec(prec)
want.Parse(test.want, 10)
z := new(big.Float).SetPrec(prec)
z.Parse(test.z, 10)
w := new(big.Float).SetPrec(prec)
w.Parse(test.w, 10)
x := bigfloat.Pow(z, w)
if x.Cmp(want) != 0 {
t.Errorf("prec = %d, Pow(%v, %v) =\ngot %g;\nwant %g", prec, test.z, test.w, x, want)
}
}
}
}
func TestPow(t *testing.T) {
for _, test := range []struct {
z, w string
want string
}{
{"1.5", "1.5", "1.8371173070873835736479630560294185439744606104925025963245194254382202830929862699048945748284801761139459509199606418436441490948783180062193379634279589146216845606457574284357225789531838276676109830092400181402243325144092030253566067045309391758849310432709781082027026621306513787250611923558785098172755465204952231278685708006003328040156619"},
{"2", "1.5", "2.8284271247461900976033774484193961571393437507538961463533594759814649569242140777007750686552831454700276924618245940498496721117014744252882429941998716628264453318550111855115999010023055641211429402191199432119405490691937240294570348372817783972191046584609686174286429016795252072559905028159793745067930926636176592812412305167047901094915006"},
{"1.5", "-1.5", "0.54433105395181735515495201660130919821465499570148225076282057050021341721273667256441320735658671884857657805035870869441308121329727940925017421138606190062864727722837257138836224561575817116077362459533037574525165407834346756306862420874990790396590549430251203206006004803871151962224035329063066957548905082088747351936846542240009860859723315"},
{"2", "-1.5", "0.35355339059327376220042218105242451964241796884423701829416993449768311961552675971259688358191039318375346155772807425623120901396268430316103037427498395785330566648187639818894998762528819551514286752738999290149256863364921550368212935466022229965238808230762107717858036270994065090699881285199742181334913658295220741015515381458809876368643757"},
} {
for _, prec := range []uint{24, 53, 64, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000} {
want := new(big.Float).SetPrec(prec)
want.Parse(test.want, 10)
z := new(big.Float).SetPrec(prec)
z.Parse(test.z, 10)
w := new(big.Float).SetPrec(prec)
w.Parse(test.w, 10)
x := bigfloat.Pow(z, w)
if x.Cmp(want) != 0 {
t.Errorf("prec = %d, Pow(%v, %v) =\ngot %g;\nwant %g", prec, test.z, test.w, x, want)
}
}
}
}
func BenchmarkPow(b *testing.B) {
z := big.NewFloat(2).SetPrec(1e5)
w := big.NewFloat(1.5).SetPrec(1e5)
_ = bigfloat.Pow(z, w) // fill pi cache before benchmarking
for _, prec := range []uint{1e2, 1e3, 1e4, 1e5} {
z = big.NewFloat(2).SetPrec(prec)
w = big.NewFloat(1.5).SetPrec(prec)
b.Run(fmt.Sprintf("%v", prec), func(b *testing.B) {
b.ReportAllocs()
for n := 0; n < b.N; n++ {
bigfloat.Pow(z, w)
}
})
}
}
func TestPowSpecialValues(t *testing.T) {
for _, f := range []struct {
z, w float64
}{
{2, +0.0},
{2, -0.0},
{4.2, 1.0},
{math.Inf(+1), 2.0},
} {
z := big.NewFloat(f.z).SetPrec(53)
w := big.NewFloat(f.w).SetPrec(53)
x64, acc := bigfloat.Pow(z, w).Float64()
want := math.Pow(f.z, f.w)
if x64 != want || acc != big.Exact {
t.Errorf("Pow(%g, %g) =\n got %g (%s);\nwant %g (Exact)", f.z, f.w, x64, acc, want)
}
}
}
func testPowFloat64(scale float64, nTests int, t *testing.T) {
for i := 0; i < nTests; i++ {
r1 := math.Abs(rand.Float64() * scale) // base always > 0
r2 := rand.Float64() * scale
z := big.NewFloat(r1).SetPrec(53)
w := big.NewFloat(r2).SetPrec(53)
x64, acc := bigfloat.Pow(z, w).Float64()
want := math.Pow(r1, r2)
// Unfortunately, the Go math.Pow function is not completely
// accurate, so it doesn't make sense to require 100%
// compatibility with it, since it happens that math.Pow
// returns a result with the last bit off (same as math.Log).
//
// Just require a relative error smaller than 1e-14.
if math.Abs(x64-want)/want > 1e-14 || acc != big.Exact {
t.Errorf("Pow(%g, %g) =\n got %g (%s);\nwant %g (Exact)", z, w, x64, acc, want)
}
}
}