Code_Aster ®
Version
8.2
Titrate:
Operator RESO_LDLT


Date:
31/01/06
Author (S):
J. Key PELLET
:
U4.55.02-I1 Page
: 1/4

Organization (S): EDF-R & D/AMA

Handbook of Utilization
U4.5- booklet: Methods of resolution
Document: U4.55.02

Operator RESO_LDLT

1 Goal

To solve a system of linear equations by a “direct” method.

The operator allows real or complex resolutions. The matrix must have been beforehand
factorized by command FACT_LDLT [U4.55.01].

In spite of its name, this command corresponds to the three established methods of “direct” resolution
in Aster: the resolution LDLT, the method multifrontale and method MUMPS. The effective choice of
method is done through command NUME_DDL [U4.61.11].

The resolution by combined gradient is done by command RESO_GRAD [U4.55.04].

Product a structure of data of the cham_no_ type *.
Handbook of Utilization
U4.5- booklet: Methods of resolution
HT-62/06/004/A

Code_Aster ®
Version
8.2
Titrate:
Operator RESO_LDLT


Date:
31/01/06
Author (S):
J. Key PELLET
:
U4.55.02-I1 Page
: 2/4

2 Syntax
U
[cham_no_ *]
=
RESO_LDLT







(reuse = U,








MATR_FACT
=
With,
/
[matr_asse_DEPL_R]
/
[matr_asse_DEPL_C]
/
[matr_asse_TEMP_R]
/
[matr_asse_TEMP_C]
/
[matr_asse_PRES_R]
/
[matr_asse_PRES_C]








CHAM_NO
=
B,
/
[cham_no_DEPL_R]
/
[cham_no_DEPL_C]
/
[cham_no_TEMP_R]
/
[cham_no_TEMP_C]
/
[cham_no_PRES_R]
/
[cham_no_PRES_C]







CHAM_CINE
= vcine,/[cham_no_DEPL_R]
/
[cham_no_TEMP_R]
/
[cham_no_PRES_C]







# if solvor MUMPS:







RESI_RELA
=/1.e-6, [DEFAUT]
/
eps
, [R]







TITER
= titr,
[l_K80]







INFO
=
/1, [DEFAUT]









/
2
,






)

if CHAM_NO:

[cham_no_DEPL_R] then [*]
- >
DEPL_R
[cham_no_DEPL_C]
DEPL_C
[cham_no_TEMP_R]
TEMP_R
[cham_no_TEMP_C]
TEMP_C
[cham_no_PRES_R]
PRES_R
[cham_no_PRES_C]
PRES_C
Handbook of Utilization
U4.5- booklet: Methods of resolution
HT-62/06/004/A

Code_Aster ®
Version
8.2
Titrate:
Operator RESO_LDLT


Date:
31/01/06
Author (S):
J. Key PELLET
:
U4.55.02-I1 Page
: 3/4

3 General information

This command makes it possible to solve the linear systems AX = B where A is a matrix
“factorized beforehand” by command FACT_LDLT [U4.51.01].

The resolution is possible for boundary conditions of DIRICHLET (boundary conditions
kinematics) dualized or eliminated [U2.01.02]. In this last case, if the loading X = X0
on the “edge” 0 was translated by a kinematic load (operator AFFE_CHAR_CINE [U4.44.03]
taking into account in the assembled matrix (operator ASSE_MATRICE [U4.61.22], the “value” of it
loading (X0), calculated by operator CALC_CHAR_CINE [U4.61.03] must be provided by the word
key CHAM_CINE.

4 Operands
4.1 Operand
MATR_FACT

MATR_FACT = A,

Name of the factorized matrix, concept produced by operator FACT_LDLT. This matrix can be
real or complex, symmetrical or not.

4.2 Operand
CHAM_NO

CHAM_NO = B
,

Name of the vector second member (in general obtained by command ASSE_VECTEUR).

4.3 Operand
CHAM_CINE


CHAM_CINE = vcine,

Name of the vector representing the “value” of the boundary conditions of the translated type “DIRICHLET”
in the form of kinematic loading (i.e. by use of one of the commands
AFFE_CHAR_CINE or AFFE_CHAR_CINE_F).

This cham_no comes from the execution of operator CALC_CHAR_CINE on the list of the char_cine
(loadings kinematics) associated assembled matrix A [U2.01.02].
4.4 Operand
RESI_RELA


RESI_RELA = 1.e-6 (defect)/eps
This key word is described in [U4.50.01]

4.5 Operand
TITER


TITER =
titr,

Titrate that one wants to give to the produced result [U4.03.01].

4.6 Operand
INFO


INFO =

1: no impression.
Handbook of Utilization
U4.5- booklet: Methods of resolution
HT-62/06/004/A

Code_Aster ®
Version
8.2
Titrate:
Operator RESO_LDLT


Date:
31/01/06
Author (S):
J. Key PELLET
:
U4.55.02-I1 Page
: 4/4

5 Examples

·
Constitution of the assembled matrices:

One calculated before the elementary terms Kel, Fel.



naked = NUME_DDL (MATR_RIGI = Kel)

Kass =
ASSE_MATRICE


(MATR_ELEM = Kel,
NUME_DDL = naked,)

Fass =
ASSE_VECTEUR


(MATR_ELEM = Fel,
NUME_DDL = naked,)

·
Factorization in place:



Kass

= FACT_LDLT
(reuse = Kass,
MATR_ASSE = Kass,

)

·
Out-place resolution:



Uass
= RESO_LDLT

(MATR_FACT = Kass, CHAM_NO = Fass,)

·
Resolution in place:

Fass =

RESO_LDLT
(reuse=Fass,
MATR_FACT=Kass, CHAM_NO=Fass,)

·
for the use of the loads kinematics (with elimination of the imposed degrees of freedom), to see
the example given in command AFFE_CHAR_CINE [U4.44.03].

Handbook of Utilization
U4.5- booklet: Methods of resolution
HT-62/06/004/A

Outline document