Fix poor randomness properties of first call to Rand.next().
#2321
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jemc
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Nov 15, 2017
packages/random/xorshift.pony
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| _y = y xor x xor (y >> 18) xor (x >> 5) | ||
| _x = y | ||
| x = x xor (x << 23) | ||
| _y = x xor y xor (x >> 18) xor (y >> 5) |
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Sorry I'm a bit slow to review this - can you explain this part of the change?
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Oops, I commited this part by accident. I'm reverting it in the new squash.
The current implementations of XorOshiro128Plus and XorShift128Plus return the sum of input seed values for the first value, which is unsafe. Rather than telling people to discard the first value, skip past it in the actual implementation. This commit also fixes the documentation of current implementations for consistency with the Random trait. Resolves #2320
jemc
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Rand.next().
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Nov 16, 2017
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Thank you! |
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The current implementations of XorOshiro128Plus and XorShift128Plus return the sum of input seed values for the first value, which is unsafe. Rather than telling people to discard the first value, skip past it in the actual implementation.
This commit also fixes the documentation of current implementations for consistency with the Random trait.
Resolves #2320