BLASFEO API

The BLASFEO API in BLASFEO is always exported.

The BLASFEO API defines C structures for matrices and vectors. These structures are used to abstract from the actual memory layout of matrices and vectors.
As an example, in case the LA backend is given by the High-Performance version, the matrices are stored in a cache-optimized format, called panel-major matrix format.
Packing and unpacking routines are provided to convert to/from column/row-major matrix format and the BLASFEO matrix structure (similarly for vectors).

All BLASFEO linear algebra routines operate on the matrix (blasfeo_dmat and blasfeo_smat) and vector (blasfeo_dmat and blasfeo_smat) structures.

BLASFEO routine API can be obtained from standard BLAS and LAPACK API using the following rules:

• the routine name begins with blasfeo_
• the char options are hard-coded at the end of the routine name.
• all BLASFEO routines are non-destructive, and then they take one extra argument reserved for the output (e.g. the BLAS dgemm routine call C = C + A * B becomes D = C + A * B in BLASFEO); the C and D matrices can alias.
• in case of matrix operands, double *A, int lda is substituted with blasfeo_dmat *sA, int ai, int aj where sA is a pointer to a BLASFEO matrix structure, ai and aj are the row- and column-indexes of the work sub-matrix.
• in case of vector operands, double *x, int incx is substituted with blasfeo_dvec *sx, int xi where sx is a pointer to a BLASFEO vector structure, xi is the indexes of the work sub-vector; vector operands can not operate on rows or columns of matrices.
• in case of scalar operands (both integers and real), input scalar operands are passed by value and not by reference.

As an example, standard BLAS API of the routine dgemv

void dgemv_(char *ta, int *n, int *m, double *alpha, double *a, int *lda, double *x, int *incx, double *beta, double *y, int *incy);

translates in the BLASFEO API routines

void blasfeo_dgemv_n(int n, int m, double alpha, struct blasfeo_dmat *sA, int ai, int aj, struct blasfeo_dvec *sx, int xi, double beta, struct blasfeo_dvec *sy, int yi, struct blasfeo_dvec *sz, int zi);

or

void blasfeo_dgemv_t(int n, int m, double alpha, struct blasfeo_dmat *sA, int ai, int aj, struct blasfeo_dvec *sx, int xi, double beta, struct blasfeo_dvec *sy, int yi, struct blasfeo_dvec *sz, int zi);

depending on the value of ta.