| // Copyright 2026 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 rewritegeneric |
| |
| import "testing" |
| |
| func TestModularMultiplicativeInverse(t *testing.T) { |
| t.Parallel() |
| |
| // We've got 63 bits of phase space for the Multiplier |
| // Needless to say this is too much to bruteforce here. |
| // I've randomly picked a range of 1<<24 because it runs in 0.03s on my machine which isn't too slow. |
| // We test both sides of the wrapping point (0 and math.MaxUint64) since we need to test something and it's a usual place to have bugs. |
| const halfRange = 1 << 23 |
| for i := -int64(halfRange) - 1; i < halfRange; i += 2 { // odd only, a bit after to a bit before the wrapping point |
| mmi := modularMultiplicativeInverse(uint64(i)) |
| |
| if uint64(i)*mmi != 1 { |
| t.Errorf("%d * modularMultiplicativeInverse(%d) != 1; modularMultiplicativeInverse(%d) == %d", i, i, i, mmi) |
| } |
| } |
| } |
