NX Nastran DMAP Programmer's Guide - Kxcad.net

1030
FBS
Matrix forward/backward substitution
8. Parallel processing in this module (Method 1A only) is selected with the
NASTRAN statement keyword PARALLEL (or SYSTEM (107)). To force parallel
processing, also specify NASTRAN FBSOPT = -2, SPARSE = 0.
9. For the sparse method the B matrix must be in machine precision. See Remarks
under the “DECOMP” on page 882 module description.
10. See the NX Nastran Numerical Methods User’s Guide for further details on the
FBS module and related topics.
Examples:
1. Solve [A] [X] = [B] where [A] could be either symmetric or unsymmetric.
DECOMP A/LD,U, $
FBS LD,U,B/X/ $
MATPRN X// $
2. Solve [A] [X] = [B] assuming [A] is symmetric (form = 6 in matrix trailer).
DECOMP A/LD,, $
FBS LD,,B/X/ $
MATPRN X// $
3. Solve [LD] [X] = [C] where [LD] is the lower triangular factor obtained in Example
2.
FBS LD,,C/X///1 $ FORWARD PASS ONLY
4. Solve [LD] T [X] = [C] where [LD] is the lower triangular factor obtained in
Example 2.
FBS LD,,C/X///-1 $ BACKWARD PASS ONLY
5. Given that [M] and [K] are symmetric and [M] is also positive definite, find
[[LD] T ] -1 [K] [LD] T , where [M] = [LD] [LD] T .
DECOMP M/LD,,//1 $ CHOLESKY
FBS LD,,K/Y///1 $ FWD.ONLY,Y AN INTERMEDIATE RESULT
FBS LD,,Y/J/2//1 $ FWD.ONLY, LEFT-HAND