This is an Ada 2012 package that provides an interface to dense linear algebra packages. Initially the focus is on BLAS, which has been covered except for routines working on banded matrices.

Other Ada interfaces to BLAS exist, but they tend to have limitations. Any Ada compiler that supports Interfaces.Fortran can compile an interface that calls the routines in BLAS, passing in Ada arrays with Convention => Fortran set or, with a little more work, mutating the operand order and the various TRANS parameters to allow Ada arrays with the default Convention to be used. Such an interface can do basic linear algebra operations, but it cannot operate on sub-slices or sub-blocks of vectors or matrices without making temporary copies.

The aim of this project is to develop a set of vector and matrix types in a tagged type hierarchy that encompasses both types that wrap 'concrete' in-memory arrays and types that provide a 'view' onto a slice or sub-block of one of the 'concrete' types. If A is an object of type Concrete_Real_Matrix, for example, then A.Row(2) will return a Real_Matrix_Vector object which can be used by any routine which requires a vector and will operate in-place on the second row of the matrix A. This requires some assumptions about ABI compatibility between Ada and Fortran on the platform in question, but in practice few problems are expected.

The Ada subprograms in LALG.Real_BLAS have the same names as in BLAS, but without the precision specifier s or d (which are unnecessary as LALG will have been instantiated for one precision or the other). Parameters relating to the size or stride of the inputs are not required, as the vector and matrix types will provide the correct values each time.

A set of unit tests has been provided. These do not test the BLAS library for correctness or accuracy. Instead they run limited checks against each routine in the Ada interface to make sure that the interfacing with the Fortran code is functional.

Two .gpr project files have been provided for those using GNAT/GPRBuild. There are two parameters - a mode parameters that can be set to debug or optimize and a blas parameter that can be set to system, netlib or openblas to select the BLAS library that you wish to link to. It may be necessary to change the 'Linker' settings in lalg_tests.gpr if your desired BLAS library is not in the expected place.

The package is provided under the ISC license:

Copyright (c) 2015 - 2022, James Humphry

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