According to upstream this program needs lots of RAM and thus for i386/amd64 the compiler flag -m64 is needed. Unfortunately this is not supported on all architectures. So on some (like mips, mipsel, kfreebsd-i386, hurd-i386, armel, armhf), that have no 64-bit mode implemented, only a 32bit version is built. Apart from the number of data that can be processed, this has no influence on the results.