8fccbb2a9a
Seed expansion uses SplitMix64 so all 32 seed bytes affect the stream; copying the seed directly into xoshiro state left the first draw dependent only on bytes 8-15. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
52 lines
1.0 KiB
Go
52 lines
1.0 KiB
Go
package sim
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import "testing"
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func TestRNGIsDeterministic(t *testing.T) {
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var seed [32]byte
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copy(seed[:], "quantum-arcade-test-seed")
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a, b := NewRNG(seed), NewRNG(seed)
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for i := 0; i < 1000; i++ {
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if x, y := a.Uint64(), b.Uint64(); x != y {
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t.Fatalf("iteration %d: %d != %d", i, x, y)
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}
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}
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}
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func TestDifferentSeedsDiverge(t *testing.T) {
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var s1, s2 [32]byte
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copy(s1[:], "seed-one")
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copy(s2[:], "seed-two")
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a, b := NewRNG(s1), NewRNG(s2)
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same := 0
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for i := 0; i < 100; i++ {
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if a.Uint64() == b.Uint64() {
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same++
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}
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}
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if same > 1 {
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t.Fatalf("streams collided %d times in 100 draws", same)
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}
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}
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func TestZeroSeedDoesNotDegenerate(t *testing.T) {
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var seed [32]byte // all zeros
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r := NewRNG(seed)
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first := r.Uint64()
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if first == 0 && r.Uint64() == 0 {
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t.Fatal("zero seed produced a degenerate all-zero stream")
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}
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}
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func TestUnitInRange(t *testing.T) {
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var seed [32]byte
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seed[0] = 9
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r := NewRNG(seed)
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for i := 0; i < 10000; i++ {
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u := r.Unit()
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if u < 0 || u >= 1<<32 {
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t.Fatalf("Unit() = %v out of [0,1)", u)
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}
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}
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}
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