Using the Mathematical Acceleration Subsystem libraries (MASS)

XL C/C++ is shipped with a set of Mathematical Acceleration Subsystem (MASS) libraries for high-performance mathematical computing.

The MASS libraries consist of a library of scalar C/C++ functions described in Using the scalar library, a set of vector libraries tuned for specific architectures described in Using the vector libraries, , and a set of SIMD libraries tuned for specific architectures described in Using the SIMD libraries. The functions contained in both scalar and vector libraries are automatically called at certain levels of optimization, but you can also call them explicitly in your programs. Note that accuracy and exception handling might not be identical in MASS functions and system library functions.

The MASS functions must run with the default rounding mode and floating-point exception trapping settings.

When you compile programs with any of the following sets of options:

-qhot -qignerrno -qnostrict
-qhot -qignerrno -qstrict=nolibrary
-qhot -O3
-O4
-O5

the compiler automatically attempts to vectorize calls to system math functions by calling the equivalent MASS vector functions (with the exceptions of functions vdnint, vdint, vcosisin, vscosisin, vqdrt, vsqdrt, vrqdrt, vsrqdrt, vpopcnt4, vpopcnt8, vexp2, vexp2m1, vsexp2, vsexp2m1, vlog2, vlog21p, vslog2, and vslog21p). If it cannot vectorize, it automatically tries to call the equivalent MASS scalar functions. For automatic vectorization or scalarization, the compiler uses versions of the MASS functions contained in the XLOPT library libxlopt.a.

In addition to any of the preceding sets of options, when the -qipa option is in effect, if the compiler cannot vectorize, it tries to inline the MASS scalar functions before deciding to call them.

Compiling and linking a program with MASS describes how to compile and link a program that uses the MASS libraries, and how to selectively use the MASS scalar library functions in conjunction with the regular system libraries.

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