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extern "C" {
int dsyev_(char *jobz, char *uplo,
int *n, double *a, int *lda,
double *w, double *work, int *lwork,
int *info);
}
void softassign::eigenvectorOfN(double *N, float* q){
static float q_pre[4]; // previous result
int dimN = 4;
double w[4]; // eigenvalues
double *work = new double; // workspace
int info;
int lwork = -1;
dsyev_((char*)"V", (char*)"U",
&dimN, N, &dimN,
w, work, &lwork, &info);
if(info != 0){
fprintf(stderr, "info = %d\n", info);
exit(1);
}
lwork = (int)work[0];
delete work;
work = new double [lwork];
dsyev_((char*)"V", (char*)"U",
&dimN, N, &dimN,
w, work, &lwork, &info);
delete [] work;
if(info != 0){
fprintf(stderr, "computing eigenvector FAIL! info = %d\n", info);
//exit(1);
// if fail, put back the previous result
for(int i=0; i<4; i++){
q[i] = q_pre[i];
}
}else{
// last column of N is the eigenvector of the largest eigenvalue
// and N is stored column-major
for(int i=0; i<4; i++){
q[i] = N[4*3 + i];
q_pre[i] = q[i];
}
}
} |
