CGEFA(3)

SYNOPSIS
SUBROUTINE CGEFA (A, LDA, N, IPVT, INFO)

NAME
cgefa - Factor a matrix using Gaussian elimination.

LIBRARY
SLATEC (LINPACK)

CATEGORY
D2C1

TYPE
COMPLEX (SGEFA-S, DGEFA-D, CGEFA-C)

KEYWORDS
GENERAL MATRIX, LINEAR ALGEBRA, LINPACK, MATRIX FACTORIZATION

AUTHOR
Moler, C. B., (U. of New Mexico)

DESCRIPTION
CGEFA factors a complex matrix by Gaussian elimination. CGEFA is usually called by CGECO, but it can be called directly with a saving in time if RCOND is not needed. (Time for CGECO) = (1 + 9/N)*(Time for CGEFA) . On Entry A COMPLEX(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 CGESL or CGEDI will divide by zero if called. Use RCOND in CGECO for a reliable indication of singularity.

REFERENCES
J. J. Dongarra, J. R. Bunch, C. B. Moler, and G. W. Stewart, LINPACK Users' Guide, SIAM, 1979.

ROUTINES CALLED
CAXPY, CSCAL, ICAMAX

REVISION HISTORY (YYMMDD)
780814 DATE WRITTEN
890831 Modified array declarations. (WRB)
890831 REVISION DATE from Version 3.2
891214 Prologue converted to Version 4.0 format. (BAB)
900326 Removed duplicate information from DESCRIPTION section. (WRB)
920501 Reformatted the REFERENCES section. (WRB)