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Update seed_rng() in stdlib to take a varying seed.

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Previously, we were trying to take a uniform seed and then shuffle that
around to initialize the state for each of the program instances.  This
was becoming increasingly untenable and brittle.

Now a varying seed is expected and used.
This commit is contained in:
Matt Pharr
2012-05-30 10:35:41 -07:00
parent 5cb53f52c3
commit 8fd9b84a80
6 changed files with 11 additions and 58 deletions
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59
stdlib.ispc
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@@ -4026,60 +4026,13 @@ static inline uniform float frandom(uniform RNGState * uniform state)
return floatbits(0x3F800000 | irand)-1.0f;
}
static inline uniform unsigned int __seed4(varying RNGState * uniform state,
uniform int start,
uniform unsigned int seed) {
uniform unsigned int c1 = 0xf0f0f0f0;
uniform unsigned int c2 = 0x0f0f0f0f;
state->z1 = insert(state->z1, start + 0, seed);
state->z1 = insert(state->z1, start + 1, seed ^ c1);
state->z1 = insert(state->z1, start + 2, (seed << 3) ^ c1);
state->z1 = insert(state->z1, start + 3, (seed << 2) ^ c2);
seed += 131;
state->z2 = insert(state->z2, start + 0, seed);
state->z2 = insert(state->z2, start + 1, seed ^ c1);
state->z2 = insert(state->z2, start + 2, (seed << 3) ^ c1);
state->z2 = insert(state->z2, start + 3, (seed << 2) ^ c2);
seed ^= extract(state->z2, 2);
state->z3 = insert(state->z3, start + 0, seed);
state->z3 = insert(state->z3, start + 1, seed ^ c1);
state->z3 = insert(state->z3, start + 2, (seed << 3) ^ c1);
state->z3 = insert(state->z3, start + 3, (seed << 2) ^ c2);
seed <<= 4;
seed += 3;
seed ^= extract(state->z1, 3);
state->z4 = insert(state->z4, start + 0, seed);
state->z4 = insert(state->z4, start + 1, seed ^ c1);
state->z4 = insert(state->z4, start + 2, (seed << 3) ^ c1);
state->z4 = insert(state->z4, start + 3, (seed << 2) ^ c2);
return seed;
}
static inline void seed_rng(varying RNGState * uniform state,
uniform unsigned int seed) {
if (programCount == 1) {
state->z1 = seed;
state->z2 = seed ^ 0xbeeff00d;
state->z3 = ((seed & 0xffff) << 16) | (seed >> 16);
state->z4 = (((seed & 0xff) << 24) | ((seed & 0xff00) << 8) |
((seed & 0xff0000) >> 8) | (seed & 0xff000000) >> 24);
}
else {
seed = __seed4(state, 0, seed);
if (programCount == 8)
__seed4(state, 4, seed ^ 0xbeeff00d);
if (programCount == 16) {
__seed4(state, 4, seed ^ 0xbeeff00d);
__seed4(state, 8, ((seed & 0xffff) << 16) | (seed >> 16));
__seed4(state, 12, (((seed & 0xff) << 24) | ((seed & 0xff00) << 8) |
((seed & 0xff0000) >> 8) | (seed & 0xff000000) >> 24));
}
}
unsigned int seed) {
state->z1 = seed;
state->z2 = seed ^ 0xbeeff00d;
state->z3 = ((seed & 0xffff) << 16) | (seed >> 16);
state->z4 = (((seed & 0xff) << 24) | ((seed & 0xff00) << 8) |
((seed & 0xff0000) >> 8) | (seed & 0xff000000) >> 24);
}
static inline void seed_rng(uniform RNGState * uniform state,