[Webkit-unassigned] [Bug 157805] REGRESSION(r192855): Math.random() always produces the same first 7 decimal points the first two invocations

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=157805

--- Comment #5 from Joseph Pecoraro <joepeck at webkit.org> ---
(In reply to comment #3)
> Probably too many zeroes in the initial seed, since our seed API is 32 bit.
> You can probably fix this by:
> 
>         uint64_t seed64 = seed;
>         m_low = (seed64 << 32) | seed64;
>         m_high = (seed64 << 32) | seed64;
> 

After this the first 4 digits stayed nearly identical:

    >>> Math.random()
    0.41647092963078913
    >>> Math.random()
    0.41646612834590113

    >>> Math.random()
    0.47840231815551537
    >>> Math.random()
    0.47839187513838377

How about we just advance once after setting the seed?

    m_low = seed;
    m_high = seed;
    advance();

Do you see any disadvantages to this?

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