From: Christian Couder <christian.couder@gmail.com>
Date: Fri, 12 Jun 2009 11:56:29 GMT
Subject: Re: [PATCH v3 0/3] automatically skip away from broken commits
Message-ID: <c07716ae0906120456j1a14af52n47c3a3542201aaf@mail.gmail.com>
In-Reply-To: <4A309083.9090907@zytor.com>

On Thu, Jun 11, 2009 at 7:05 AM, H. Peter Anvin<hpa@zytor.com> wrote:
>
> Urk, I managed to get myself completely confused -- I did the series
> approximation on the wrong side of inverting the function.  The correct
> power is actually 1.5 (over the range 0 to 1), a value > 1 is necessary
> to bias the PRNG toward the beginning (x = 0) of the list.

I started working on this, but I wonder if it's better to add a
#include <math.h> and link with -lm than to provide a custom sqrt
implementation. Too bad the best power is not 2.

To implement the PRNG, I guess that using something based on the
function given by "man 3 rand" should be ok:

int get_prn(int count) {
    count = count * 1103515245 + 12345;
    return((unsigned)(count/65536) % 32768);
}

where the "count" we pass is the count of elements in the list rather
than the static seed.

Best regards,
Christian.