-------- Original Message -------- Subject: Re: Handling of floating point numbers changed from GMP 4.1.4 to GMP 4.2.1 Date: Thu, 13 Sep 2007 14:42:12 +0200 From: Paul Zimmermann Paul.Zimmermann@loria.fr To: Roberto Bagnara bagnara@cs.unipr.it CC: Vincent.Lefevre@ens-lyon.fr, tg@swox.com
Roberto,
I tried your program on a Pentium 4, under Linux, with gmp-4.1.4, gmp-4.2.1, and gmp-4.2.2, for all 4 rounding modes, compiled like this:
mermoz% g++ -I/users/spaces/logiciels/gmp-4.1.4/p4/include bagnara.c /users/spaces/logiciels/gmp-4.1.4/p4/lib/libgmpxx.a /users/spaces/logiciels/gmp-4.1.4/p4/lib/libgmp.a -lm
I get 121.83249999999999602 in all cases, except with gmp-4.1.4 and FE_UPWARD, where I get 121.83250000000001023, which is wrong, since it is larger than 137171200400403985/1125899906842624, whereas the documentation says that mpq_get_d rounds towards zero.
Thus I confirm there was a problem in 4.1.4, and it is now fixed, i.e., mpq_get_d does not depend any more on the processor rounding mode, and returns the correct result (at least for that example, and on my machine).
Paul