DGEFA(3F)DGEFA(3F)NAMEDGEFA - DGEFA factors a double precision matrix by Gaussian
elimination.
DGEFA is usually called by DGECO, but it can be called directly with a
saving in time if RCOND is not needed. (Time for DGECO) = (1 +
9/N)*(Time for DGEFA) .
SYNOPSYS
SUBROUTINE DGEFA(A,LDA,N,IPVT,INFO)
DESCRIPTION
On Entry
A DOUBLE PRECISION(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 DGESL or DGEDI will divide by zero
if called. Use RCOND in DGECO 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 DAXPY,DSCAL,IDAMAX
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