MUMPS interface function
dmumps - call to MUMPS
Calling Sequence
- [id]=dmumps (id [,mat])
Input Parameters
-
mat
: sparse matrix which has to be provided as the second argument of
dmumps if id.JOB is strictly larger than 0.
-
id.SYM
: controls the matrix type (symmetric positive
definite, symmetric indefinite or unsymmetric) and it has do be
initialized by the user before the initialization phase of MUMPS
(see id.JOB). Its value is set to 0 after the call of initmumps.
-
id.JOB
: defines the action that will be realized by
MUMPS: initialize, analyze and/or factorize and/or solve and
release MUMPS internal C/Fortran data. It has to be set by the user before
any call to MUMPS (except after a call to initmumps, which sets
its value to -1).
-
id.ICNTL and id.CNTL
: define control parameters that can be
set after the initialization call (id.JOB = -1). See Section ``Control parameters''
of the MUMPS user's guide
for more details.
If the user does not modify an entry in id.ICNTL then MUMPS
uses the default parameter. For example, if the user wants to
use the AMD ordering, he/she should set id.ICNTL(7) = 0.
Note that the following
parameters are inhibited because they are automatically set
within the interface: id.ICNTL(19) which controls the Schur
complement option and id.ICNTL(20) which controls the
format of the right-hand side.
Note that parameters id.ICNTL(1:4) may not work properly
depending on your compiler and your environment. In case of
problem, we recommand to swith printing off by setting
id.ICNL(1:4)=-1.
-
id.PERM_IN
: corresponds to the given ordering option
(see Section ``Input and output parameters''
of the MUMPS user's guide
for more details). Note that this permutation is only accessed if
the parameter id.ICNTL(7) is set to 1.
-
id.COLSCA and id.ROWSCA
: are optional scaling arrays (see Section
``Input and output parameters''
of the MUMPS user's guide
for more details)
-
id.RHS
: defines the right-hand side. The parameter id.ICNTL(20) related to its format (sparse or dense) is automatically set within the interface. Note that id.RHS is not modified (as in MUMPS), the solution is returned in id.SOL.
-
id.VAR_SCHUR
: corresponds to the list of variables
that appear in the Schur complement matrix (see Section
``Input and output parameters''
of the MUMPS user's guide
for more details).
-
id.REDRHS
(input parameter only if id.VAR_SCHUR was provided during the factorization and
if ICNTL(26)=2 on entry to the solve phase): partial
solution on the variables corresponding to the Schur complement. It is provided
by the user and normally results from both the Schur complement and the reduced right-hand
side that were returned by MUMPS in a previous call. When ICNTL(26)=2, MUMPS uses this information
to build the solution id.SOL on the complete problem.
See Section ``Schur complement''
of the MUMPS user's guide
for more details.
Output Parameters
-
id.SCHUR
: if id.VAR_SCHUR is provided of size SIZE_SCHUR, then
id.SCHUR corresponds to a dense array of size
(SIZE_SCHUR,SIZE_SCHUR) that holds the Schur
complement matrix (see Section
``Input and output parameters''
of the MUMPS user's guide
for more details). The user does not have to initialize it.
-
id.REDRHS
(output parameter only if ICNTL(26)=1 and id.VAR_SCHUR was defined): Reduced right-hand side (or
condensed right-hand side on the variables associated to the Schur complement). It
is computed by MUMPS during the solve stage if ICNTL(26)=1. It can then be used
outside MUMPS, together with the Schur complement, to build a solution on the interface.
See Section ``Schur complement''
of the MUMPS user's guide
for more details.
-
id.INFOG and id.RINFOG
: information parameters
(see Section ``Information parameters''
of the MUMPS user's guide
).
-
id.SYM_PERM
: corresponds to a symmetric permutation
of the variables
(see discussion regarding ICNTL(7) in Section
``Control parameters''
of the MUMPS user's guide
). This permutation is computed during the analysis and is
followed by the numerical factorization except when numerical
pivoting occurs.
-
id.UNS_PERM
: column permutation (if any) on exit from the analysis
phase of MUMPS
(see discussion regarding ICNTL(6) in Section
``Control parameters''
of the MUMPS user's guide
).
-
id.SOL
: dense vector or matrix containing the solution after MUMPS
solution phase. Also contains the nullspace in case of
null space computation, or entries of the inverse, in case of
computation of inverse entries.
Internal Parameters
-
-
id.INST: (MUMPS reserved component) MUMPS internal parameter.
-
id.TYPE: (MUMPS reserved component) defines the arithmetic
(complex or double precision).
Description
The function dmumps solves systems of
linear equations of the form Ax = b where A is square sparse matrix and b
is a dense or sparse vector or matrix. The solver MUMPS is used and
we refer the user to the MUMPS User's Guide for full details.
Before the first call to dmumps, a call to initmumps must have been done:
[id]=initmumps();
Examples
// this is a small linear system
// whose solution is [1;2;3;4;5]
A = sparse( [ 2 3 4 0 0;
3 0 -3 0 6;
0 -1 1 2 0;
0 0 2 0 0;
0 4 0 0 1] );
b = [20 ; 24; 9; 6; 13];
// initialization of the MUMPS structure (here job=-1)
id=initmumps();
[id]=dmumps(id);
id.RHS=b;
// call to MUMPS for the resolution
id.JOB=6;
[id]=dmumps(id,A);
x=id.SOL
norm(A*x-b)
// Destruction of the MUMPS instance
id.JOB=-2;
[id]=dmumps(id);
See also the examples provided in the directory "examples" that
comes with the distribution of this interface.
See Also
initmumps, zmumps,
References
http://graal.ens-lyon.fr/MUMPS/
http://www.enseeiht.fr/apo/MUMPS/