.. _D4.01.02:

**d4.01.02** Some underground data structures
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**Summary:**

Some "underground" data structures are described here. These are the ones that can be accessed in the code without passing as an argument because their name is known a prima facie. This is only possible because these SDs are "unique" (a kind of global variable).

*Note:*

*To better understand the concepts mentioned in the* SD*subterranes related to parallelism and linear solvers, you can consult the documents:*


*D4.01.03 (*Distributed data structure and parallelism), *


*U2.08.06 (*Parallelism user manual), *


*U4.50.01 (Keyword* *SOLVEUR) .*




.. toctree::
    :hidden:

    self

.. toctree::
    :maxdepth: 2
    :numbered:

    Liste_des_SD_souterraines
    SD___MUMPS______
    SD___CALCUL_PARALLELE_