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precision of 64 vs 32 bit gfortran compilers; with additional details


Sorry I did not give enough details in the first email. I was thinking it would be an easy answer like real variable default for the 32 bit gfortran is 4 bytes and 8 bytes for the 64 bit gfortran. 

I have included original email below along with more details. I appreciate all the quick replies and excellent advice I have gotten from the group.

Thanks, Mike 



original message:

I am running a nonlinear finite element problem on both a 32 bit Intel Centrino 
Duo and an AMD64 3200 machine. The identical problem cannot reach convergence on 
the 32 bit machine but converges on the 64 bit machine. Does the 64 bit gfortran 
have greater precision in floating point and integer numbers?



additional details:

My version of gfortran:

[root@localhost ~]# gfortran -v
Using built-in specs.
Target: x86_64-redhat-linux
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man --infodir=/usr/share/info --enable-shared --enable-threads=posix --enable-checking=release --with-system-zlib --enable-__cxa_atexit --disable-libunwind-exceptions --enable-libgcj-multifile --enable-languages=c,c++,objc,obj-c++,java,fortran,ada --enable-java-awt=gtk --disable-dssi --enable-plugin --with-java-home=/usr/lib/jvm/java-1.4.2-gcj-1.4.2.0/jre --with-cpu=generic --host=x86_64-redhat-linux
Thread model: posix
gcc version 4.1.1 20070105 (Red Hat 4.1.1-51)

I am using the same version and OS on the 32 bit machine.




compiler options used for both compilers can be seen in the attached make file. The only difference in the make files is where it searches for libX11.so:   LIBS = /usr/lib64/libX11.so







Thanks, Mike

Attachment: nike3d_gfortran.mak
Description: Binary data


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