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  • 2022.1
  • 12/20/2021
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SSYEVX Example Program in C

/******************************************************************************* * 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. * ******************************************************************************** */ /* SSYEVX Example. ============== Program computes the smallest eigenvalues and the corresponding eigenvectors of a real symmetric matrix A: 6.29 -0.39 0.61 1.18 -0.08 -0.39 7.19 0.81 1.19 -0.08 0.61 0.81 5.48 -3.13 0.22 1.18 1.19 -3.13 3.79 -0.26 -0.08 -0.08 0.22 -0.26 0.83 Description. ============ The routine computes selected eigenvalues and, optionally, eigenvectors of an n-by-n real symmetric matrix A. The eigenvector v(j) of A satisfies A*v(j) = lambda(j)*v(j) where lambda(j) is its eigenvalue. The computed eigenvectors are orthonormal. Eigenvalues and eigenvectors can be selected by specifying either a range of values or a range of indices for the desired eigenvalues. Example Program Results. ======================== SSYEVX Example Program Results The total number of eigenvalues found: 3 Selected eigenvalues 0.71 0.82 6.58 Selected eigenvectors (stored columnwise) 0.22 0.09 -0.95 0.21 0.08 -0.04 -0.52 -0.22 -0.29 -0.73 -0.21 -0.09 -0.32 0.94 0.01 */ #include <stdlib.h> #include <stdio.h> /* SSYEVX prototype */ extern void ssyevx( char* jobz, char* range, char* uplo, int* n, float* a, int* lda, float* vl, float* vu, int* il, int* iu, float* abstol, int* m, float* w, float* z, int* ldz, float* work, int* lwork, int* iwork, int* ifail, int* info ); /* Auxiliary routines prototypes */ extern void print_matrix( char* desc, int m, int n, float* a, int lda ); /* Parameters */ #define N 5 #define NSELECT 3 #define LDA N #define LDZ N /* Main program */ int main() { /* Locals */ int n = N, il, iu, m, lda = LDA, ldz = LDZ, info, lwork; float abstol, vl, vu; float wkopt; float* work; /* Local arrays */ /* iwork dimension should be at least 5*n */ int iwork[5*N], ifail[N]; float w[N], z[LDZ*NSELECT]; float a[LDA*N] = { 6.29f, 0.00f, 0.00f, 0.00f, 0.00f, -0.39f, 7.19f, 0.00f, 0.00f, 0.00f, 0.61f, 0.81f, 5.48f, 0.00f, 0.00f, 1.18f, 1.19f, -3.13f, 3.79f, 0.00f, -0.08f, -0.08f, 0.22f, -0.26f, 0.83f }; /* Executable statements */ printf( " SSYEVX Example Program Results\n" ); /* Negative abstol means using the default value */ abstol = -1.0; /* Set il, iu to compute NSELECT smallest eigenvalues */ il = 1; iu = NSELECT; /* Query and allocate the optimal workspace */ lwork = -1; ssyevx( "Vectors", "Indices", "Upper", &n, a, &lda, &vl, &vu, &il, &iu, &abstol, &m, w, z, &ldz, &wkopt, &lwork, iwork, ifail, &info ); lwork = (int)wkopt; work = (float*)malloc( lwork*sizeof(float) ); /* Solve eigenproblem */ ssyevx( "Vectors", "Indices", "Upper", &n, a, &lda, &vl, &vu, &il, &iu, &abstol, &m, w, z, &ldz, work, &lwork, iwork, ifail, &info ); /* Check for convergence */ if( info > 0 ) { printf( "The algorithm failed to compute eigenvalues.\n" ); exit( 1 ); } /* Print the number of eigenvalues found */ printf( "\n The total number of eigenvalues found:%2i\n", m ); /* Print eigenvalues */ print_matrix( "Selected eigenvalues", 1, m, w, 1 ); /* Print eigenvectors */ print_matrix( "Selected eigenvectors (stored columnwise)", n, m, z, ldz ); /* Free workspace */ free( (void*)work ); exit( 0 ); } /* End of SSYEVX Example */ /* Auxiliary routine: printing a matrix */ void print_matrix( char* desc, int m, int n, float* a, int lda ) { 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" ); } }

Product and Performance Information

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