Generates the real orthogonal matrix Q determined by ?sptrd.
lapack_int LAPACKE_sopgtr (int matrix_layout, char uplo, lapack_int n, const float* ap, const float* tau, float* q, lapack_int ldq);
lapack_int LAPACKE_dopgtr (int matrix_layout, char uplo, lapack_int n, const double* ap, const double* tau, double* q, lapack_int ldq);
The routine explicitly generates the n-by-n orthogonal matrix Q formed by sptrd when reducing a packed real symmetric matrix A to tridiagonal form: A = Q*T*QT. Use this routine after a call to ?sptrd.
Specifies whether matrix storage layout is row major (LAPACK_ROW_MAJOR) or column major (LAPACK_COL_MAJOR).
Must be 'U' or 'L'. Use the same uplo as supplied to ?sptrd.
The order of the matrix Q (n≥ 0).
- ap, tau
Arrays ap and tau, as returned by ?sptrd.
The size of ap must be at least max(1, n(n+1)/2).
The size of tau must be at least max(1, n-1).
The leading dimension of the output array q; at least max(1, n).
Array, size (size max(1, ldq*n)) .
Contains the computed matrix Q.
This function returns a value info.
If info=0, the execution is successful.
If info = -i, the i-th parameter had an illegal value.
The computed matrix Q differs from an exactly orthogonal matrix by a matrix E such that ||E||2 = O(ε), where ε is the machine precision.
The approximate number of floating-point operations is (4/3)n3.
The complex counterpart of this routine is upgtr.