SGEFA(3F)							     SGEFA(3F)

NAME    [Toc]    [Back]

     SGEFA   - SGEFA factors a real matrix by Gaussian elimination.

     SGEFA is usually called by	SGECO, but it can be called directly with a
     saving in time if	RCOND  is not needed.  (Time for SGECO)	= (1 +
     9/N)*(Time	for SGEFA) .

SYNOPSYS    [Toc]    [Back]

      SUBROUTINE SGEFA(A,LDA,N,IPVT,INFO)

DESCRIPTION    [Toc]    [Back]

     On	Entry

     A REAL(LDA, N)
	the matrix to be factored.

     LDA INTEGER
	the leading dimension of the array  A .

     N INTEGER
	the order of the matrix	 A .  On Return

     A an upper	triangular matrix and the multipliers
	which were used	to obtain it.
	The factorization can be written  A = L*U , where
	L  is a	product	of permutation and unit	lower
	triangular matrices and	 U  is upper triangular.

     IPVT INTEGER(N)
	an integer vector of pivot indices.

     INFO INTEGER
	= 0  normal value.
	= K  if	 U(K,K)	.EQ. 0.0 .  This is not	an error
	condition for this subroutine, but it does
	indicate that SGESL or SGEDI will divide by zero
	if called.  Use	 RCOND	in SGECO for a reliable
	indication of singularity.  LINPACK.  This version dated 08/14/78 .
     Cleve Moler, University of	New Mexico, Argonne National Lab.  Subroutines
     and Functions BLAS	SAXPY,SSCAL,ISAMAX


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