check out this thread, I think I got it from here…but not sure (mine is v2.19 for windows)…CalculiX i8 and mingw - #7 by jbr

anyway 64GB of ram should be enough for about 2 Million equations (dofs) according to the manual, so keep it in mind.

from the installation guide http://www.dhondt.de/ccx_2.20.README.INSTALL :

USING CALCULIX with 8 byte per integer

This may be necessary for really big models. Right now, there is a file

Makefile_i8 showing you how it works. The integers in the FORTRAN files must

be compiled with the option -fdefault-integer-8 (for the GNU compiler). This

tells the compiler to consider all integers in the FORTRAN files as

8-byte integers. For the C-files, the flag -DLONGLONG must be added to the

CFLAGS. Right now, the CalculiX distribution assumes that you also generate

a integer*8 version of ARPACK (use the above FORTRAN flag) and an
integer*8 version of PARDISO (of course only if you use any if these, i.e.

if you have the flags -DPARDISO and -DARPACK in your Makefile). The

SPOOLES distribution, however, is assumed to be an integer

*4, since it*

is not known that an integer8 version of SPOOLES has already been made.

is not known that an integer