ZGELSS(l)								 )								 ZGELSS(l)

NAME

       ZGELSS - compute the minimum norm solution to a complex linear least squares problem

SYNOPSIS

       SUBROUTINE ZGELSS( M, N, NRHS, A, LDA, B, LDB, S, RCOND, RANK, WORK, LWORK, RWORK, INFO )

	   INTEGER	  INFO, LDA, LDB, LWORK, M, N, NRHS, RANK

	   DOUBLE	  PRECISION RCOND

	   DOUBLE	  PRECISION RWORK( * ), S( * )

	   COMPLEX*16	  A( LDA, * ), B( LDB, * ), WORK( * )

PURPOSE

       ZGELSS computes the minimum norm solution to a complex linear least squares problem: Minimize 2-norm(| b - A*x |).

       using the singular value decomposition (SVD) of A. A is an M-by-N matrix which may be rank-deficient.

       Several	right  hand side vectors b and solution vectors x can be handled in a single call; they are stored as the columns of the M-by-NRHS
       right hand side matrix B and the N-by-NRHS solution matrix X.

       The effective rank of A is determined by treating as zero those singular values which are less than RCOND times the largest singular value.

ARGUMENTS

       M       (input) INTEGER
	       The number of rows of the matrix A. M >= 0.

       N       (input) INTEGER
	       The number of columns of the matrix A. N >= 0.

       NRHS    (input) INTEGER
	       The number of right hand sides, i.e., the number of columns of the matrices B and X. NRHS >= 0.

       A       (input/output) COMPLEX*16 array, dimension (LDA,N)
	       On entry, the M-by-N matrix A.  On exit, the first min(m,n) rows of A are overwritten with its right singular vectors, stored  row-
	       wise.

       LDA     (input) INTEGER
	       The leading dimension of the array A. LDA >= max(1,M).

       B       (input/output) COMPLEX*16 array, dimension (LDB,NRHS)
	       On  entry,  the	M-by-NRHS  right hand side matrix B.  On exit, B is overwritten by the N-by-NRHS solution matrix X.  If m >= n and
	       RANK = n, the residual sum-of-squares for the solution in the i-th column is given by the sum of squares of elements n+1:m in  that
	       column.

       LDB     (input) INTEGER
	       The leading dimension of the array B.  LDB >= max(1,M,N).

       S       (output) DOUBLE PRECISION array, dimension (min(M,N))
	       The singular values of A in decreasing order.  The condition number of A in the 2-norm = S(1)/S(min(m,n)).

       RCOND   (input) DOUBLE PRECISION
	       RCOND is used to determine the effective rank of A.  Singular values S(i) <= RCOND*S(1) are treated as zero.  If RCOND < 0, machine
	       precision is used instead.

       RANK    (output) INTEGER
	       The effective rank of A, i.e., the number of singular values which are greater than RCOND*S(1).

       WORK    (workspace/output) COMPLEX*16 array, dimension (LWORK)
	       On exit, if INFO = 0, WORK(1) returns the optimal LWORK.

       LWORK   (input) INTEGER
	       The dimension of the array WORK. LWORK >= 1, and also: LWORK >=	2*min(M,N) + max(M,N,NRHS) For good performance, LWORK should gen-
	       erally be larger.

	       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.

       RWORK   (workspace) DOUBLE PRECISION array, dimension (5*min(M,N))

       INFO    (output) INTEGER
	       = 0:  successful exit
	       < 0:  if INFO = -i, the i-th argument had an illegal value.
	       > 0:  the algorithm for computing the SVD failed to converge; if INFO = i, i off-diagonal elements of  an  intermediate	bidiagonal
	       form did not converge to zero.

LAPACK version 3.0						   15 June 2000 							 ZGELSS(l)