Generalities
===========

A NUME_DDLsert to define the numbering of the unknowns (and equations) of a linear system. We recall that the unknowns of such a system are components carried by nodes from MAILLAGE (or late nodes from LIGREL).

The matrices that we want to describe are square, sparse, symmetric or not.

When a matrix is non-symmetric, its sparse structure is symmetric.

The numbering of the unknowns of a system is similar to that of the components of a CHAM_NO. Moreover, SD NUME_EQUA described in this document is the one referenced by SD CHAM_NO [D4.06.05 - Field Data Structure].

SD NUME_DDLcontient also describes the arrays for storing values of assembled matrices [:external:ref:`D4.06.10 - Structure de Données sd_matr_asse <D4.06.10 - Structure de Données sd_matr_asse>`]. We call STOCKAGEcette part of the data structure.

Dependency relationships between these objects can be represented by:


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.. _RefImage_100000000000021A0000024DE467716FDB93F559.png:

**Figure** 1-a **: Links of NUME_DDL, NUME_EQUA**, and **STOCKAGE to other data structures**