Hello Peter !
Every day is a day to learn something new !
Thank you for reply !
Indeed using this option I'm getting identical outputs.
With the modifications I did to GLPK 4.65 (one of then to allow
eliminate "xassert" defining "-DNDEBUG") https://github.com/mingodad/GLPK
====
CFLAGS="-g -O3 -march=native -ffp-contract=off -DWITH_SPLAYTREE -DNDEBUG
-flto" ./configure
====
Cheers !
On 17/7/20 18:04, Peter Cawley wrote:
Perhaps you are looking for -ffp-contract=off. With the
default -ffp-contract=fast, GCC will make use of FMA instructions if
the -march architecture supports them. FMA instructions are usually
more accurate than separate multiply then add, but do not give bitwise
identical results to a multiply followed by an add (because FMA has no
rounding step between the multiply and the add).
On Fri, Jul 17, 2020 at 4:34 PM Domingo Alvarez Duarte
<[email protected] <mailto:[email protected]>> wrote:
Hello !
Doing tests with GLPK I noticed that if I compile it with
"-march=native
-g -O2" on a computer with an "i7" processor the solution for several
files change, the objective function result remain the same but other
values varies from model to model.
Example dist.mod:
====
6 rlim[w96] NU 3 0 3 -11283.2 #
only -O2
====
6 rlim[w96] NU 3 0 3 -11283.1 #
-O2 -march=native
====
Example mfasp.mod:
====
1 r[1,2] 9 1 # only -O2
2 r[2,3] 2 1
====
1 r[1,2] 1 1 # -O2
-march=native
2 r[2,3] 10 1
====
Cheers !
