To duplicate the double-precision results of programs on systems with different floating-point architectures (without multiply-add instructions), specify the nomaf suboption of the -qfloat option. This suboption prevents the compiler from generating any multiply-add operations. This results in decreased accuracy and performance but provides strict conformance to the IEEE standard for double-precision arithmetic.
To duplicate the results of programs where the default size of REAL items is different from that on systems running XL Fortran, use the -qrealsize option (page -qrealsize Option) to change the default REAL size when compiling with XL Fortran.
If the system whose results you want to duplicate preserves full double precision for default real constants that are assigned to DOUBLE PRECISION variables, use the -qdpc or -qrealsize option.
If results consistent with other systems are important to you, include norsqrt and nofold in the settings for the -qfloat option. If you specify the option -O3, include -qstrict too.