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  • 2022.1
  • 12/20/2021
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SSYEV 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. * ******************************************************************************** */ /* SSYEV Example. ============== Program computes all eigenvalues and eigenvectors of a real symmetric matrix A: 1.96 -6.49 -0.47 -7.20 -0.65 -6.49 3.80 -6.39 1.50 -6.34 -0.47 -6.39 4.17 -1.51 2.67 -7.20 1.50 -1.51 5.70 1.80 -0.65 -6.34 2.67 1.80 -7.10 Description. ============ The routine computes all 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. Example Program Results. ======================== SSYEV Example Program Results Eigenvalues -11.07 -6.23 0.86 8.87 16.09 Eigenvectors (stored columnwise) -0.30 -0.61 0.40 -0.37 0.49 -0.51 -0.29 -0.41 -0.36 -0.61 -0.08 -0.38 -0.66 0.50 0.40 0.00 -0.45 0.46 0.62 -0.46 -0.80 0.45 0.17 0.31 0.16 */ #include <stdlib.h> #include <stdio.h> /* SSYEV prototype */ extern void ssyev( char* jobz, char* uplo, int* n, float* a, int* lda, float* w, float* work, int* lwork, int* info ); /* Auxiliary routines prototypes */ extern void print_matrix( char* desc, int m, int n, float* a, int lda ); /* Parameters */ #define N 5 #define LDA N /* Main program */ int main() { /* Locals */ int n = N, lda = LDA, info, lwork; float wkopt; float* work; /* Local arrays */ float w[N]; float a[LDA*N] = { 1.96f, 0.00f, 0.00f, 0.00f, 0.00f, -6.49f, 3.80f, 0.00f, 0.00f, 0.00f, -0.47f, -6.39f, 4.17f, 0.00f, 0.00f, -7.20f, 1.50f, -1.51f, 5.70f, 0.00f, -0.65f, -6.34f, 2.67f, 1.80f, -7.10f }; /* Executable statements */ printf( " SSYEV Example Program Results\n" ); /* Query and allocate the optimal workspace */ lwork = -1; ssyev( "Vectors", "Upper", &n, a, &lda, w, &wkopt, &lwork, &info ); lwork = (int)wkopt; work = (float*)malloc( lwork*sizeof(float) ); /* Solve eigenproblem */ ssyev( "Vectors", "Upper", &n, a, &lda, w, work, &lwork, &info ); /* Check for convergence */ if( info > 0 ) { printf( "The algorithm failed to compute eigenvalues.\n" ); exit( 1 ); } /* Print eigenvalues */ print_matrix( "Eigenvalues", 1, n, w, 1 ); /* Print eigenvectors */ print_matrix( "Eigenvectors (stored columnwise)", n, n, a, lda ); /* Free workspace */ free( (void*)work ); exit( 0 ); } /* End of SSYEV 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" ); } }

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