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

[Corinna Vinschen <vinschen@redhat.com>]

On Feb 11 12:16, 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
> 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
> 

Thanks, pushed.

However, there's still something wrong with your patch file.  In all
lines with spaces following tabs, your patch is missing exactly one
space.  Please check this locally.


Thanks,
Corinna