dgelq2 - compute the LQ factorization of a general rectangular matrix using an unblocked algorithm
SUBROUTINE DGELQ2(M, N, A, LDA, TAU, WORK, INFO) INTEGER INFO, LDA, M, N DOUBLE PRECISION A(LDA,*), TAU(*), WORK(*) SUBROUTINE DGELQ2_64(M, N, A, LDA, TAU, WORK, INFO) INTEGER*8 INFO, LDA, M, N DOUBLE PRECISION A(LDA,*), TAU(*), WORK(*) F95 INTERFACE SUBROUTINE GELQ2(M, N, A, LDA, TAU, WORK, INFO) INTEGER :: M, N, LDA, INFO REAL(8), DIMENSION(:,:) :: A REAL(8), DIMENSION(:) :: TAU, WORK SUBROUTINE GELQ2_64(M, N, A, LDA, TAU, WORK, INFO) INTEGER(8) :: M, N, LDA, INFO REAL(8), DIMENSION(:,:) :: A REAL(8), DIMENSION(:) :: TAU, WORK C INTERFACE #include <sunperf.h> void dgelq2 (int m, int n, double *a, int lda, double *tau, int *info); void dgelq2_64 (long m, long n, double *a, long lda, double *tau, long *info);
Oracle Solaris Studio Performance Library dgelq2(3P) NAME dgelq2 - compute the LQ factorization of a general rectangular matrix using an unblocked algorithm SYNOPSIS SUBROUTINE DGELQ2(M, N, A, LDA, TAU, WORK, INFO) INTEGER INFO, LDA, M, N DOUBLE PRECISION A(LDA,*), TAU(*), WORK(*) SUBROUTINE DGELQ2_64(M, N, A, LDA, TAU, WORK, INFO) INTEGER*8 INFO, LDA, M, N DOUBLE PRECISION A(LDA,*), TAU(*), WORK(*) F95 INTERFACE SUBROUTINE GELQ2(M, N, A, LDA, TAU, WORK, INFO) INTEGER :: M, N, LDA, INFO REAL(8), DIMENSION(:,:) :: A REAL(8), DIMENSION(:) :: TAU, WORK SUBROUTINE GELQ2_64(M, N, A, LDA, TAU, WORK, INFO) INTEGER(8) :: M, N, LDA, INFO REAL(8), DIMENSION(:,:) :: A REAL(8), DIMENSION(:) :: TAU, WORK C INTERFACE #include <sunperf.h> void dgelq2 (int m, int n, double *a, int lda, double *tau, int *info); void dgelq2_64 (long m, long n, double *a, long lda, double *tau, long *info); PURPOSE dgelq2 computes an LQ factorization of a real m by n matrix A: A=L*Q. ARGUMENTS M (input) M is INTEGER The number of rows of the matrix A. M >= 0. N (input) N is INTEGER The number of columns of the matrix A. N >= 0. A (input/output) A is DOUBLE PRECISION array, dimension (LDA,N) On entry, the m by n matrix A. On exit, the elements on and below the diagonal of the array contain the m by min(m,n) lower trapezoidal matrix L (L is lower triangular if m <= n); the elements above the diagonal, with the array TAU, represent the orthogonal matrix Q as a product of elementary reflectors (see Further Details). LDA (input) LDA is INTEGER The leading dimension of the array A. LDA >= max(1,M). TAU (output) TAU is DOUBLE PRECISION array, dimension (min(M,N)) The scalar factors of the elementary reflectors (see Further Details). WORK (output) WORK is DOUBLE PRECISION array, dimension (M) INFO (output) INFO is INTEGER = 0: successful exit, < 0: if INFO = -i, the i-th argument had an illegal value. FURTHER DETAILS The matrix Q is represented as a product of elementary reflectors Q = H(k) . . . H(2) H(1), where k = min(m,n). Each H(i) has the form H(i) = I - tau * v * v**T where tau is a complex scalar, and v is a complex vector with v(1:i-1) = 0 and v(i) = 1; conjg(v(i+1:n)) is stored on exit in A(i,i+1:n), and tau in TAU(i). 7 Nov 2015 dgelq2(3P)