dualfroz
351ba05ff4
The a-real / b-non-real branch of Quo divided the real numerator by each component of b independently, which is not complex division: (1+0i)/(1+i) returned 1+1i instead of 0.5-0.5i, (1+0i)/i returned +Inf+1i, and (0+0i)/i divided 0/0 and panicked. Use the full a*conj(b)/|b|^2 formula (the same one the general branch uses), which reduces correctly when a is real. Closes #577
40 lines
1.2 KiB
Go
40 lines
1.2 KiB
Go
package bignum
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import (
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"math/big"
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"testing"
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"github.com/stretchr/testify/require"
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)
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func TestComplexMultiplierQuo(t *testing.T) {
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const prec = 128
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newComplex := func(re, im float64) *Complex {
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return &Complex{
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new(big.Float).SetPrec(prec).SetFloat64(re),
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new(big.Float).SetPrec(prec).SetFloat64(im),
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}
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}
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f := func(v float64) *big.Float { return new(big.Float).SetPrec(prec).SetFloat64(v) }
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cm := NewComplexMultiplier()
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for _, tc := range []struct {
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name string
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a, b *Complex
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wantRe, wantIm float64
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}{
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// Real numerator, non-real denominator: the previously broken branch.
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{"1/(1+i)", newComplex(1, 0), newComplex(1, 1), 0.5, -0.5},
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{"1/i", newComplex(1, 0), newComplex(0, 1), 0, -1},
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{"0/i", newComplex(0, 0), newComplex(0, 1), 0, 0}, // must not panic
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// General complex division (regression guard for the other branch).
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{"(2+3i)/(1+i)", newComplex(2, 3), newComplex(1, 1), 2.5, 0.5},
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} {
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c := newComplex(0, 0)
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cm.Quo(tc.a, tc.b, c)
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require.Zerof(t, c[0].Cmp(f(tc.wantRe)), "%s real: got %v, want %v", tc.name, c[0], tc.wantRe)
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require.Zerof(t, c[1].Cmp(f(tc.wantIm)), "%s imag: got %v, want %v", tc.name, c[1], tc.wantIm)
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}
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}
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