Visible to Intel only — GUID: GUID-C176AF71-9A01-4940-A445-8327C8C7AD34
Visible to Intel only — GUID: GUID-C176AF71-9A01-4940-A445-8327C8C7AD34
?ungtr
Generates the complex unitary matrix Q determined by ?hetrd.
Syntax
lapack_int LAPACKE_cungtr (int matrix_layout, char uplo, lapack_int n, lapack_complex_float* a, lapack_int lda, const lapack_complex_float* tau);
lapack_int LAPACKE_zungtr (int matrix_layout, char uplo, lapack_int n, lapack_complex_double* a, lapack_int lda, const lapack_complex_double* tau);
Include Files
- mkl.h
Description
The routine explicitly generates the n-by-n unitary matrix Q formed by ?hetrd when reducing a complex Hermitian matrix A to tridiagonal form: A = Q*T*QH. Use this routine after a call to ?hetrd.
Input Parameters
- matrix_layout
-
Specifies whether matrix storage layout is row major (LAPACK_ROW_MAJOR) or column major (LAPACK_COL_MAJOR).
- uplo
-
Must be 'U' or 'L'.
Use the same uplo as supplied to ?hetrd.
- n
-
The order of the matrix Q (n≥ 0).
- a, tau
-
Arrays:
a (size max(1, lda*n)) is the array a as returned by ?hetrd.
tau is the array tau as returned by ?hetrd.
The dimension of tau must be at least max(1, n-1).
- lda
-
The leading dimension of a; at least max(1, n).
Output Parameters
- a
-
Overwritten by the unitary matrix Q.
Return Values
This function returns a value info.
If info=0, the execution is successful.
If info = -i, the i-th parameter had an illegal value.
Application Notes
The computed matrix Q differs from an exactly unitary 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 (16/3)n3.
The real counterpart of this routine is orgtr.