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.help dmat Jun99 "Slalib Package"
.nf
SUBROUTINE slDMAT (N, A, Y, D, JF, IW)
- - - - -
D M A T
- - - - -
Matrix inversion & solution of simultaneous equations
(double precision)
For the set of n simultaneous equations in n unknowns:
A.Y = X
where:
A is a non-singular N x N matrix
Y is the vector of N unknowns
X is the known vector
DMATRX computes:
the inverse of matrix A
the determinant of matrix A
the vector of N unknowns
Arguments:
symbol type dimension before after
N i no. of unknowns unchanged
A d (N,N) matrix inverse
Y d (N) vector solution
D d - determinant
* JF i - singularity flag
IW i (N) - workspace
* JF is the singularity flag. If the matrix is non-singular,
JF=0 is returned. If the matrix is singular, JF=-1 & D=0D0 are
returned. In the latter case, the contents of array A on return
are undefined.
Algorithm:
Gaussian elimination with partial pivoting.
Speed:
Very fast.
Accuracy:
Fairly accurate - errors 1 to 4 times those of routines optimized
for accuracy.
P.T.Wallace Starlink 7 February 1995
Copyright (C) 1995 Rutherford Appleton Laboratory
Copyright (C) 1995 Association of Universities for Research in Astronomy Inc.
.fi
.endhelp
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