func TestSqrt(t *testing.T) {
tests := []struct {
prec uint
in float64
}{
{16, 0},
{16, 1},
{16, 4},
{16, 10000},
{16, 2},
{64, 2},
{256, 2},
{1024, 1.5},
}
for _, test := range tests {
x := new(big.Float).SetPrec(test.prec)
x.SetFloat64(test.in)
var got, got2, diff big.Float
pslq := New(test.prec)
pslq.Sqrt(x, &got)
got2.SetPrec(test.prec).Mul(&got, &got)
diff.Sub(&got2, x)
if diff.MinPrec() > 1 {
t.Errorf("sqrt(%f) prec %d wrong got %.20f square %.20f expecting %f diff %g minprec %d", test.in, test.prec, &got, &got2, x, &diff, diff.MinPrec())
}
}
}
func (p *exporter) float(x *Mpflt) {
// extract sign (there is no -0)
f := &x.Val
sign := f.Sign()
if sign == 0 {
// x == 0
p.int(0)
return
}
// x != 0
// extract exponent such that 0.5 <= m < 1.0
var m big.Float
exp := f.MantExp(&m)
// extract mantissa as *big.Int
// - set exponent large enough so mant satisfies mant.IsInt()
// - get *big.Int from mant
m.SetMantExp(&m, int(m.MinPrec()))
mant, acc := m.Int(nil)
if acc != big.Exact {
Fatalf("exporter: internal error")
}
p.int(sign)
p.int(exp)
p.string(string(mant.Bytes()))
}
func (p *exporter) float(x constant.Value) {
if x.Kind() != constant.Float {
log.Fatalf("gcimporter: unexpected constant %v, want float", x)
}
// extract sign (there is no -0)
sign := constant.Sign(x)
if sign == 0 {
// x == 0
p.int(0)
return
}
// x != 0
var f big.Float
if v, exact := constant.Float64Val(x); exact {
// float64
f.SetFloat64(v)
} else if num, denom := constant.Num(x), constant.Denom(x); num.Kind() == constant.Int {
// TODO(gri): add big.Rat accessor to constant.Value.
r := valueToRat(num)
f.SetRat(r.Quo(r, valueToRat(denom)))
} else {
// Value too large to represent as a fraction => inaccessible.
// TODO(gri): add big.Float accessor to constant.Value.
f.SetFloat64(math.MaxFloat64) // FIXME
}
// extract exponent such that 0.5 <= m < 1.0
var m big.Float
exp := f.MantExp(&m)
// extract mantissa as *big.Int
// - set exponent large enough so mant satisfies mant.IsInt()
// - get *big.Int from mant
m.SetMantExp(&m, int(m.MinPrec()))
mant, acc := m.Int(nil)
if acc != big.Exact {
log.Fatalf("gcimporter: internal error")
}
p.int(sign)
p.int(exp)
p.string(string(mant.Bytes()))
}
func emitBig(b *big.Float) string {
digits := bits2digits(b.MinPrec())
return b.Text('e', int(digits))
}