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Improve RNG documentation.

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Issue #390.
This commit is contained in:
Matt Pharr
2012-10-03 08:33:43 -07:00
parent ec2e9b5e79
commit 360cc8044e
1 changed files with 8 additions and 1 deletions
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9
docs/ispc.rst
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@@ -3461,9 +3461,16 @@ library. State for the RNG is maintained in an instance of the
::
struct RNGState;
void seed_rng(varying RNGState * uniform state, int seed)
void seed_rng(varying RNGState * uniform state, varying int seed)
void seed_rng(uniform RNGState * uniform state, uniform int seed)
Note that if the same ``varying`` seed value is used for all of the program
instances (e.g. ``RNGState state; seed_rng(&state, 1);``), then all of the
program instances in the gang will see the same sequence of pseudo-random
numbers. If this behavior isn't desred, you may want to add the
``programIndex`` value to the provided seed or otherwise ensure that the
seed has a unique value for each program instance.
After the RNG is seeded, the ``random()`` function can be used to get a
pseudo-random ``unsigned int32`` value and the ``frandom()`` function can
be used to get a pseudo-random ``float`` value.