◆ zungtr()

Generates a transform matrix from a complex Hermitian matrix to tridiagonal form

Purpose: This routine generates a complex unitary matrix Q which is defined as the product of n - 1 elementary reflectors of order n, as returned by zhetrd.
If uplo = 'U', Q = H(n-1) . . . H(2) H(1).

If uplo = 'L', Q = H(1) H(2) . . . H(n-1).

Parameters

[in]	uplo	= 'U': Upper triangle of a[][] contains elementary reflectors from zhetrd. = 'L': Lower triangle of a[][] contains elementary reflectors from zhetrd.
[in]	n	Order of the matrix Q. (n >= 0) (If n = 0, returns without computation)
[in]	lda	Leading dimension of the two dimensional array a[][]. (lda >= max(1, n))
[in,out]	a[][]	Array a[la][lda] (la >= n) [in] The vectors which define the elementary reflectors, as returned by zhetrd. [out] The n x n unitary matrix Q.
[in]	tau[]	Array tau[ltau] (ltau >= n - 1) tau[i] must contain the scalar factor of the elementary reflector H(i), as returned by zhetrd.
[out]	work[]	Array work[lwork] Work array. On exit, if info = 0, work[0] returns the optimal lwork.
[in]	lwork	The size of work[]. (lwork >= max(1, n-1)) For optimum performance lwork >= (n-1)*nb, where nb is the optimal blocksize. If lwork = -1, then a workspace query is assumed. The routine only calculates the optimal size of the work[] array, and returns the value in work[0].
[out]	info	= 0: Successful exit. = -1: The argument uplo had an illegal value. (uplo != 'U' nor 'L') = -2: The argument n had an illegal value. (n < 0) = -3: The argument lda had an illegal value. (lda < max(1, n)) = -7: The argument lwork had an illegal value. (lwork too small)