CUNGQL(3)

okay bestie, welcome to the cungql.f(3) page from the Library Functions Manual — yes, the one and only ✨

💅 NAME 💅

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/cungql.f

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✨ SYNOPSIS ✨

Functions/Subroutines — the icon itself:

subroutine CUNGQL (m, n, k, a, lda, tau, work, lwork, info)
    CUNGQL

The CUNGQL girlie is here to generate your complex matrix Q, no cap 💫

🎀 Function/Subroutine Documentation 🎀

subroutine CUNGQL (integer m, integer n, integer k, complex, dimension( lda,
* ) a, integer lda, complex, dimension( * ) tau, complex, dimension( * )
work, integer lwork, integer info)
    CUNGQL

🎯 Purpose 🎯

okay so listen: CUNGQL generates an M-by-N complex matrix Q with orthonormal columns. It’s defined as the last N columns of a product of K elementary reflectors of order M:

Q  =  H(k) . . . H(2) H(1)

as returned by CGEQLF. periodt 💅

🌸 Parameters 🌸

• M — M is INTEGER. It’s the number of rows of the matrix Q. Requirement: M >= 0.
• N — N is INTEGER. It’s the number of columns of the matrix Q. Requirement: M >= N >= 0.
• K — K is INTEGER. It’s the number of elementary reflectors whose product defines the matrix Q. Requirement: N >= K >= 0.
• A — A is COMPLEX array, dimension (LDA,N). On entry, the (n-k+i)-th column must contain the vector which defines the elementary reflector H(i), for i = 1,2,...,k, as returned by CGEQLF in the last k columns of its array argument A. On exit, it’s the M-by-N matrix Q. glow-up complete ✨
• LDA — LDA is INTEGER. The first dimension of the array A. Requirement: LDA >= max(1,M).
• TAU — TAU is COMPLEX array, dimension (K). TAU(i) must contain the scalar factor of the elementary reflector H(i), as returned by CGEQLF.
• WORK — WORK is COMPLEX array, dimension (MAX(1,LWORK)). On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
• LWORK — LWORK is INTEGER. The dimension of the array WORK. Requirement: LWORK >= max(1,N). For optimum performance, LWORK >= N*NB, where NB is the optimal blocksize.

🫶 special case alert: if LWORK = -1, then a workspace query is assumed; the routine only calculates the optimal size of the WORK array, returns this value as the first entry of the WORK array, and no error message related to LWORK is issued by XERBLA.

• INFO — INFO is INTEGER. = 0: successful exit. < 0: if INFO = -i, the i-th argument has an illegal value.

💖 Author 💖

• Univ. of Tennessee
• Univ. of California Berkeley
• Univ. of Colorado Denver
• NAG Ltd.

Definition at line 127 of file cungql.f.

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🌈 Author 🌈

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