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Re: [PATCH] Fix cos computation for multiple precision fallback (bz #20357)
On 18/07/2016 12:59, Siddhesh Poyarekar wrote:
> On Mon, Jul 18, 2016 at 09:47:43AM -0500, Paul E. Murphy wrote:
>>> diff --git a/sysdeps/ieee754/dbl-64/s_sin.c b/sysdeps/ieee754/dbl-64/s_sin.c
>>> index ca2532f..7c9a079 100644
>>> --- a/sysdeps/ieee754/dbl-64/s_sin.c
>>> +++ b/sysdeps/ieee754/dbl-64/s_sin.c
>>> @@ -803,7 +803,7 @@ sloww (double x, double dx, double orig, int k)
>>> a = t - y;
>>> da = ((t - a) - y) + da;
>>>
>>> - if (n == 2 || n == 1)
>>> + if (n & 2)
>>
>> That looks ok. I had to do double check the unification. It wasn't
>> immediately obvious this was correct.
>
> Yeah, the n == 1 check in csloww had thrown me off the last time - it
> is because the input to csloww was always in quadrant 0 or 1 (0.855469
> <|x| <2.426265) and hence the check for n == 2 is unnecessary in that
> context. Rotating that by pi/2 for sin is consistent with the n & 2
> check.
>
>>> @@ -817,7 +817,7 @@ sloww (double x, double dx, double orig, int k)
>>> if (w[0] == w[0] + cor)
>>> return (a > 0) ? w[0] : -w[0];
>>>
>>> - return (n & 1) ? __mpcos (orig, 0, true) : __mpsin (orig, 0, true);
>>> + return k ? __mpcos (orig, 0, true) : __mpsin (orig, 0, true);
>>
>> OK, that fix looks fairly obvious after reviewing commit
>> b300455644e2945da05eb49d12d3a037f1408be1.
>
> Thanks. Adhemerval, do you want to take another look at this or is it
> OK if I commit it?
LGTM!