Developer Reference for Intel® oneAPI Math Kernel Library - C

Developer Reference

  • 2021.1
  • 12/04/2020
  • Public Content
Contents

C Interface Conventions for LAPACK Routines

The C interfaces are implemented for most of the
Intel® oneAPI Math Kernel Library
 LAPACK driver and computational routines.

NaN checking in LAPACKE

NaN checking can affect the performance of an application. By default, it is ON.
See the Support Functions section for details on the methods and options to turn NaN check off or back on with LAPACKE:.

Function Prototypes

Intel® oneAPI Math Kernel Library
 supports four distinct floating-point precisions. Each corresponding prototype looks similar, usually differing only in the data type. C interface LAPACK function names follow the form
<?><name>
, where
<?>
 is:
  • LAPACKE_s
     for float
  • LAPACKE_d
     for double
  • LAPACKE_c
     for lapack_complex_float
  • LAPACKE_z
     for lapack_complex_double
A specific example follows. To solve a system of linear equations with a packed Cholesky-factored Hermitian positive-definite matrix with complex precision, use the following:
lapack_int LAPACKE_
c
pptrs
(int
matrix_layout
, char
uplo
, lapack_int
n
, lapack_int
nrhs
, const
lapack_complex_float
*
ap
,
lapack_complex_float
*
b
, lapack_int
ldb
);

Workspace Arrays

In contrast to the Fortran interface, the LAPACK C interface omits workspace parameters because workspace is allocated during runtime and released upon completion of the function operation.
If you prefer to allocate workspace arrays yourself, the LAPACK C interface provides alternate interfaces with
work
 parameters. The name of the alternate interface is the same as the LAPACK C interface with
_work
 appended. For example, the syntax for the singular value decomposition of a real bidiagonal matrix is:
Fortran:
call sbdsdc ( uplo, compq, n, d, e, u, ldu, vt, ldvt, q, iq,
work
,
iwork
, info )
C LAPACK interface:
lapack_int LAPACKE_sbdsdc ( int matrix_layout, char uplo, char compq, lapack_int n, float* d, float* e, float* u, lapack_int ldu, float* vt, lapack_int ldvt, float* q, lapack_int* iq );
Alternate C LAPACK interface with
work
 parameters:
lapack_int LAPACKE_sbdsdc_work( int matrix_layout, char uplo, char compq, lapack_int n, float* d, float* e, float* u, lapack_int ldu, float* vt, lapack_int ldvt, float* q, lapack_int* iq, float*
work
, lapack_int*
iwork
 );
See the
install_dir
/include/mkl_lapacke.h
 file for the full list of alternative C LAPACK interfaces.
The
Intel® oneAPI Math Kernel Library
 Fortran-specific documentation contains details about workspace arrays.

Mapping Fortran Data Types against C Data Types

Fortran Data Types vs. C Data Types
FORTRAN
C
INTEGER
lapack_int
LOGICAL
lapack_logical
REAL
float
DOUBLE PRECISION
double
COMPLEX
lapack_complex_float
COMPLEX*16
/
DOUBLE COMPLEX
lapack_complex_double
CHARACTER
char

C Type Definitions

You can find type definitions specific to
Intel® oneAPI Math Kernel Library
 such as
MKL_INT
,
MKL_Complex8
, and
MKL_Complex16
 in
install_dir
/mkl_types.h
.
C types 
#ifndef lapack_int
#define lapack_int MKL_INT
#endif

#ifndef lapack_logical
#define lapack_logical lapack_int
#endif
Complex Type Definitions
Complex type for single precision: 
#ifndef lapack_complex_float
#define lapack_complex_float   MKL_Complex8
#endif
Complex type for double precision: 
#ifndef lapack_complex_double
#define lapack_complex_double   MKL_Complex16
#endif
Matrix Layout Definitions 
#define LAPACK_ROW_MAJOR  101
#define LAPACK_COL_MAJOR  102
See
Matrix Layout for LAPACK Routines
 above for an explanation of row-major order and column-major order storage.
Error Code Definitions 
#define LAPACK_WORK_MEMORY_ERROR       -1010  /* Failed to allocate memory  
                                            for a working array */
#define LAPACK_TRANSPOSE_MEMORY_ERROR  -1011  /* Failed to allocate memory 
                                            for transposed matrix */

Product and Performance Information

1

Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex.