Using FLENS-LAPACK as CXXLAPACK Font-End

FLENS-LAPACK not only provides a generic implementation for a set of certain LAPACK functions. It also serves as a high-level interface for CXXLAPACK. In this respect it follows the ideas introduced on the previous pages.

Generic or External LAPACK: How to select?

Consider a LAPACK function like xGETRF. In FLENS-LAPACK we provide its functionality through the routine lapack::trf. Using macros you can control whether it calls a generic implementation or an external LAPACK implementation:

By default and if possible FLENS-LAPACK will always call the generic implementation of a LAPACK routine.
If the USE_CXXLAPACK macro is defined and no generic implementation is available then the external implementation gets called. This happens through the CXXLAPCK layer.
If the ALWAYS_USE_CXXLAPACK macro is defined then all FLENS-LAPACK routines will delegate functionality to the external LAPACK implementation. If you define this macro then the USE_CXXLAPACK gets automatically defined (see lapack-header).

You can be even more selective. For each function call you can explicitly specify whether the generic or external function gets called:

lapack::generic::trf_impl is the generic implementation of lapack::trf and
lapack::external::trf_impl is a high-level interface for cxxlapack::getrf.