I recently tried to use the LAPACKE interface, but ran into an issue that I would like to have your opinion.

It appears my program fails to compile when I include "lapacke.h" because of some interaction with variables or functions named as the single letter "I". I could reproduce the problem in one of the LAPACKE example file (see below), by adding a dummy (global) function as:

void I(){ return; };

giving the compilation error:

example_DGESV_rowmajor.c:83:6: error: expected identifier or ‘(’ before ‘__extension__’

I tried to have a look at the header file lapacke.h, e.g. for preprecessor definitions of I, but could not locate a potential source for this problem...

Many thanks for your help!

____________________________ example_DGESV_rowmajor.c ____________________________

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/*

LAPACKE_dgesv Example.

======================

The program computes the solution to the system of linear

equations with a square matrix A and multiple

right-hand sides B, where A is the coefficient matrix:

6.80 -6.05 -0.45 8.32 -9.67

-2.11 -3.30 2.58 2.71 -5.14

5.66 5.36 -2.70 4.35 -7.26

5.97 -4.44 0.27 -7.17 6.08

8.23 1.08 9.04 2.14 -6.87

and B is the right-hand side matrix:

4.02 -1.56 9.81

6.19 4.00 -4.09

-8.22 -8.67 -4.57

-7.57 1.75 -8.61

-3.03 2.86 8.99

Description.

============

The routine solves for X the system of linear equations A*X = B,

where A is an n-by-n matrix, the columns of matrix B are individual

right-hand sides, and the columns of X are the corresponding

solutions.

The LU decomposition with partial pivoting and row interchanges is

used to factor A as A = P*L*U, where P is a permutation matrix, L

is unit lower triangular, and U is upper triangular. The factored

form of A is then used to solve the system of equations A*X = B.

Example Program Results.

========================

LAPACKE_dgesv (row-major, high-level) Example Program Results

Solution

-0.80 -0.39 0.96

-0.70 -0.55 0.22

0.59 0.84 1.90

1.32 -0.10 5.36

0.57 0.11 4.04

Details of LU factorization

8.23 1.08 9.04 2.14 -6.87

0.83 -6.94 -7.92 6.55 -3.99

0.69 -0.67 -14.18 7.24 -5.19

0.73 0.75 0.02 -13.82 14.19

-0.26 0.44 -0.59 -0.34 -3.43

Pivot indices

5 5 3 4 5

*/

#include <stdlib.h>

#include <stdio.h>

#include "lapacke.h"

/* Auxiliary routines prototypes */

extern void print_matrix( char* desc, lapack_int m, lapack_int n, double* a, lapack_int lda );

extern void print_int_vector( char* desc, lapack_int n, lapack_int* a );

void I(){ return; };

/* Parameters */

#define N 5

#define NRHS 3

#define LDA N

#define LDB NRHS

/* Main program */

int main() {

/* Locals */

lapack_int n = N, nrhs = NRHS, lda = LDA, ldb = LDB, info;

/* Local arrays */

lapack_int ipiv[N];

double a[LDA*N] = {

6.80, -6.05, -0.45, 8.32, -9.67,

-2.11, -3.30, 2.58, 2.71, -5.14,

5.66, 5.36, -2.70, 4.35, -7.26,

5.97, -4.44, 0.27, -7.17, 6.08,

8.23, 1.08, 9.04, 2.14, -6.87

};

double b[LDB*N] = {

4.02, -1.56, 9.81,

6.19, 4.00, -4.09,

-8.22, -8.67, -4.57,

-7.57, 1.75, -8.61,

-3.03, 2.86, 8.99

};

/* Print Entry Matrix */

print_matrix( "Entry Matrix A", n, n, a, lda );

/* Print Right Rand Side */

print_matrix( "Right Rand Side", n, nrhs, b, ldb );

printf( "\n" );

/* Executable statements */

printf( "LAPACKE_dgesv (row-major, high-level) Example Program Results\n" );

/* Solve the equations A*X = B */

info = LAPACKE_dgesv( LAPACK_ROW_MAJOR, n, nrhs, a, lda, ipiv,

b, ldb );

/* Check for the exact singularity */

if( info > 0 ) {

printf( "The diagonal element of the triangular factor of A,\n" );

printf( "U(%i,%i) is zero, so that A is singular;\n", info, info );

printf( "the solution could not be computed.\n" );

exit( 1 );

}

/* Print solution */

print_matrix( "Solution", n, nrhs, b, ldb );

/* Print details of LU factorization */

print_matrix( "Details of LU factorization", n, n, a, lda );

/* Print pivot indices */

print_int_vector( "Pivot indices", n, ipiv );

exit( 0 );

} /* End of LAPACKE_dgesv Example */

/* Auxiliary routine: printing a matrix */

void print_matrix( char* desc, lapack_int m, lapack_int n, double* a, lapack_int lda ) {

lapack_int i, j;

printf( "\n %s\n", desc );

for( i = 0; i < m; i++ ) {

for( j = 0; j < n; j++ ) printf( " %6.2f", a[i*lda+j] );

printf( "\n" );

}

}

/* Auxiliary routine: printing a vector of integers */

void print_int_vector( char* desc, lapack_int n, lapack_int* a ) {

lapack_int j;

printf( "\n %s\n", desc );

for( j = 0; j < n; j++ ) printf( " %6i", a[j] );

printf( "\n" );

}