Visible to Intel only — GUID: GUID-817EC1F1-D0D4-4383-8D91-0F02B3606AEA
LAPACKE_sgels Example Program in C for Column Major Data Layout
/*******************************************************************************
* Copyright (C) 2009-2015 Intel Corporation. All Rights Reserved.
* The information and material ("Material") provided below is owned by Intel
* Corporation or its suppliers or licensors, and title to such Material remains
* with Intel Corporation or its suppliers or licensors. The Material contains
* proprietary information of Intel or its suppliers and licensors. The Material
* is protected by worldwide copyright laws and treaty provisions. No part of
* the Material may be copied, reproduced, published, uploaded, posted,
* transmitted, or distributed in any way without Intel's prior express written
* permission. No license under any patent, copyright or other intellectual
* property rights in the Material is granted to or conferred upon you, either
* expressly, by implication, inducement, estoppel or otherwise. Any license
* under such intellectual property rights must be express and approved by Intel
* in writing.
*
********************************************************************************
*/
/*
LAPACKE_sgels Example.
======================
Program computes the least squares solution to the overdetermined linear
system A*X = B with full rank matrix A using QR factorization,
where A is the coefficient matrix:
1.44 -7.84 -4.39 4.53
-9.96 -0.28 -3.24 3.83
-7.55 3.24 6.27 -6.64
8.34 8.09 5.28 2.06
7.08 2.52 0.74 -2.47
-5.45 -5.70 -1.19 4.70
and B is the right-hand side matrix:
8.58 9.35
8.26 -4.43
8.48 -0.70
-5.28 -0.26
5.72 -7.36
8.93 -2.52
Description.
============
The routine solves overdetermined or underdetermined real linear systems
involving an m-by-n matrix A, or its transpose, using a QR or LQ
factorization of A. It is assumed that A has full rank.
Several right hand side vectors b and solution vectors x can be handled
in a single call; they are stored as the columns of the m-by-nrhs right
hand side matrix B and the n-by-nrhs solution matrix X.
Example Program Results.
========================
LAPACKE_sgels (column-major, high-level) Example Program Results
Solution
-0.45 0.25
-0.85 -0.90
0.71 0.63
0.13 0.14
Residual sum of squares for the solution
195.36 107.06
Details of QR factorization
-17.54 -4.76 -1.96 0.42
-0.52 12.40 7.88 -5.84
-0.40 -0.14 -5.75 4.11
0.44 -0.66 -0.20 -7.78
0.37 -0.26 -0.17 -0.15
-0.29 0.46 0.41 0.24
*/
#include <stdlib.h>
#include <stdio.h>
#include "mkl_lapacke.h"
/* Auxiliary routines prototypes */
extern void print_matrix( char* desc, MKL_INT m, MKL_INT n, float* a, MKL_INT lda );
extern void print_vector_norm( char* desc, MKL_INT m, MKL_INT n, float* a, MKL_INT lda );
/* Parameters */
#define M 6
#define N 4
#define NRHS 2
#define LDA M
#define LDB M
/* Main program */
int main() {
/* Locals */
MKL_INT m = M, n = N, nrhs = NRHS, lda = LDA, ldb = LDB, info;
/* Local arrays */
float a[LDA*N] = {
1.44f, -9.96f, -7.55f, 8.34f, 7.08f, -5.45f,
-7.84f, -0.28f, 3.24f, 8.09f, 2.52f, -5.70f,
-4.39f, -3.24f, 6.27f, 5.28f, 0.74f, -1.19f,
4.53f, 3.83f, -6.64f, 2.06f, -2.47f, 4.70f
};
float b[LDB*NRHS] = {
8.58f, 8.26f, 8.48f, -5.28f, 5.72f, 8.93f,
9.35f, -4.43f, -0.70f, -0.26f, -7.36f, -2.52f
};
/* Executable statements */
printf( "LAPACKE_sgels (column-major, high-level) Example Program Results\n" );
/* Solve the equations A*X = B */
info = LAPACKE_sgels( LAPACK_COL_MAJOR, 'N', m, n, nrhs, a, lda,
b, ldb );
/* Check for the full rank */
if( info > 0 ) {
printf( "The diagonal element %i of the triangular factor ", info );
printf( "of A is zero, so that A does not have full rank;\n" );
printf( "the least squares solution could not be computed.\n" );
exit( 1 );
}
/* Print least squares solution */
print_matrix( "Least squares solution", n, nrhs, b, ldb );
/* Print residual sum of squares for the solution */
print_vector_norm( "Residual sum of squares for the solution", m-n, nrhs,
&b[n], ldb );
/* Print details of QR factorization */
print_matrix( "Details of QR factorization", m, n, a, lda );
exit( 0 );
} /* End of LAPACKE_sgels Example */
/* Auxiliary routine: printing a matrix */
void print_matrix( char* desc, MKL_INT m, MKL_INT n, float* a, MKL_INT lda ) {
MKL_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+j*lda] );
printf( "\n" );
}
}
/* Auxiliary routine: printing norms of matrix columns */
void print_vector_norm( char* desc, MKL_INT m, MKL_INT n, float* a, MKL_INT lda ) {
MKL_INT i, j;
float norm;
printf( "\n %s\n", desc );
for( j = 0; j < n; j++ ) {
norm = 0.0;
for( i = 0; i < m; i++ ) norm += a[i+j*lda] * a[i+j*lda];
printf( " %6.2f", norm );
}
printf( "\n" );
}
Parent topic: SGELS Example