Re: [PATCH 1/2] Improve lgammaf range for very small cases

[Corinna Vinschen <vinschen@redhat.com>]

Hi Andoni,

On Feb  9 17:28, Andoni Arregi wrote:
> The original cut for small arguments at |x|<2**-70 (copied from the
> double version) produces that when computing nadj we get a subnormal
> number for t*x and thus, the division of pi/subnormal will be INF and
> the logarithm of it too, which is wrong as a result for lgammaf in this
> range.
> The proposed new limit seems to be safe and has been tested to
> produce accurate results.
> (Courtesy of Andreas Jung, ESA)
> ---
>  newlib/libm/math/erf_lgamma.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/newlib/libm/math/erf_lgamma.c
> b/newlib/libm/math/erf_lgamma.c

This is broken.  It should be on one line, so apparently your
mailer broke it via autowrapping lines.

> index f88f63092..84d02159b 100644
> --- a/newlib/libm/math/erf_lgamma.c
> +++ b/newlib/libm/math/erf_lgamma.c
> @@ -168,7 +168,7 @@ static float zero=  0.0000000000e+00;
>  	       *signgamp = -1;
>  	   return one/(x-x);
>  	}
> -	if(ix<0x1c800000) {	/* |x|<2**-70, return -log(|x|) */
> +	if(ix<0x30800000) {	/* |x|<2**-30, return -log(|x|) */
>  	   if(hx<0) {
>  	       *signgamp = -1;
>  	       return -__ieee754_logf(-x);
> -- 
> 2.35.1

But even if I fix this manually, your patch doesn't apply, neither with
`git am', nor with `patch -p1'.  I have to admit that I don't understand
why...

Another question, would you mind to send patch series with a cover letter,
please?


Thanks,
Corinna