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// Copyright 2010 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 runtime_test

import (
        "math"
        "math/rand"
        . "runtime"
        "testing"
)

// turn uint64 op into float64 op
func fop(f func(x, y uint64) uint64) func(x, y float64) float64 {
        return func(x, y float64) float64 {
                bx := math.Float64bits(x)
                by := math.Float64bits(y)
                return math.Float64frombits(f(bx, by))
        }
}

func add(x, y float64) float64 { return x + y }
func sub(x, y float64) float64 { return x - y }
func mul(x, y float64) float64 { return x * y }
func div(x, y float64) float64 { return x / y }

func TestFloat64(t *testing.T) {
        base := []float64{
                0,
                math.Copysign(0, -1),
                -1,
                1,
                math.NaN(),
                math.Inf(+1),
                math.Inf(-1),
                0.1,
                1.5,
                1.9999999999999998,     // all 1s mantissa
                1.3333333333333333,     // 1.010101010101...
                1.1428571428571428,     // 1.001001001001...
                1.112536929253601e-308, // first normal
                2,
                4,
                8,
                16,
                32,
                64,
                128,
                256,
                3,
                12,
                1234,
                123456,
                -0.1,
                -1.5,
                -1.9999999999999998,
                -1.3333333333333333,
                -1.1428571428571428,
                -2,
                -3,
                1e-200,
                1e-300,
                1e-310,
                5e-324,
                1e-105,
                1e-305,
                1e+200,
                1e+306,
                1e+307,
                1e+308,
        }
        all := make([]float64, 200)
        copy(all, base)
        for i := len(base); i < len(all); i++ {
                all[i] = rand.NormFloat64()
        }

        test(t, "+", add, fop(Fadd64), all)
        test(t, "-", sub, fop(Fsub64), all)
        if GOARCH != "386" { // 386 is not precise!
                test(t, "*", mul, fop(Fmul64), all)
                test(t, "/", div, fop(Fdiv64), all)
        }
}

// 64 -hw-> 32 -hw-> 64
func trunc32(f float64) float64 {
        return float64(float32(f))
}

// 64 -sw->32 -hw-> 64
func to32sw(f float64) float64 {
        return float64(math.Float32frombits(F64to32(math.Float64bits(f))))
}

// 64 -hw->32 -sw-> 64
func to64sw(f float64) float64 {
        return math.Float64frombits(F32to64(math.Float32bits(float32(f))))
}

// float64 -hw-> int64 -hw-> float64
func hwint64(f float64) float64 {
        return float64(int64(f))
}

// float64 -hw-> int32 -hw-> float64
func hwint32(f float64) float64 {
        return float64(int32(f))
}

// float64 -sw-> int64 -hw-> float64
func toint64sw(f float64) float64 {
        i, ok := F64toint(math.Float64bits(f))
        if !ok {
                // There's no right answer for out of range.
                // Match the hardware to pass the test.
                i = int64(f)
        }
        return float64(i)
}

// float64 -hw-> int64 -sw-> float64
func fromint64sw(f float64) float64 {
        return math.Float64frombits(Fintto64(int64(f)))
}

var nerr int

func err(t *testing.T, format string, args ...interface{}) {
        t.Errorf(format, args...)

        // cut errors off after a while.
        // otherwise we spend all our time
        // allocating memory to hold the
        // formatted output.
        if nerr++; nerr >= 10 {
                t.Fatal("too many errors")
        }
}

func test(t *testing.T, op string, hw, sw func(float64, float64) float64, all []float64) {
        for _, f := range all {
                for _, g := range all {
                        h := hw(f, g)
                        s := sw(f, g)
                        if !same(h, s) {
                                err(t, "%g %s %g = sw %g, hw %g\n", f, op, g, s, h)
                        }
                        testu(t, "to32", trunc32, to32sw, h)
                        testu(t, "to64", trunc32, to64sw, h)
                        testu(t, "toint64", hwint64, toint64sw, h)
                        testu(t, "fromint64", hwint64, fromint64sw, h)
                        testcmp(t, f, h)
                        testcmp(t, h, f)
                        testcmp(t, g, h)
                        testcmp(t, h, g)
                }
        }
}

func testu(t *testing.T, op string, hw, sw func(float64) float64, v float64) {
        h := hw(v)
        s := sw(v)
        if !same(h, s) {
                err(t, "%s %g = sw %g, hw %g\n", op, v, s, h)
        }
}

func hwcmp(f, g float64) (cmp int, isnan bool) {
        switch {
        case f < g:
                return -1, false
        case f > g:
                return +1, false
        case f == g:
                return 0, false
        }
        return 0, true // must be NaN
}

func testcmp(t *testing.T, f, g float64) {
        hcmp, hisnan := hwcmp(f, g)
        scmp, sisnan := Fcmp64(math.Float64bits(f), math.Float64bits(g))
        if hcmp != scmp || hisnan != sisnan {
                err(t, "cmp(%g, %g) = sw %v, %v, hw %v, %v\n", f, g, scmp, sisnan, hcmp, hisnan)
        }
}

func same(f, g float64) bool {
        if math.IsNaN(f) && math.IsNaN(g) {
                return true
        }
        if math.Copysign(1, f) != math.Copysign(1, g) {
                return false
        }
        return f == g
}