On 2018-11-19 15:26:00 +0100, Richard Biener wrote: > On Mon, 19 Nov 2018, Vincent Lefevre wrote: > > AFAIK, GCC already changes the exponent range to the binary64 one > > (the lack of subnormals is not an issue, because in case of underflow, > > GCC ignores the computations done with MPFR). > > GCC does ignore results in case of overflow or underflow but it > doesn't currently limit mpfrs exponent range. Or rather most > languages don't - I do see mpfr_set_e{min,max} calls being > done in the Fortran frontend only, but only temporarily and > seemingly only to call mpfr_subnormalize.
Thanks for the clarification. FYI, mpfr_subnormalize was added for gfortran. > > But for its internal computations, I assume that mpc extends the > > exponent range (if it didn't you would have the same kind of problem, > > but much more often). Here it seems that the issue is that the maximum > > supported exponent range is not large enough for the chosen algorithm > > (which may not be the right one for this kind of input). > > It happens that limiting the range makes the CPOW computation fast. Yes, because for some functions, underflow or overflow can be detected before the actual computation. -- Vincent Lefèvre <vinc...@vinc17.net> - Web: <https://www.vinc17.net/> 100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/> Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon) _______________________________________________ gmp-bugs mailing list gmp-bugs@gmplib.org https://gmplib.org/mailman/listinfo/gmp-bugs