Mechanical APDL Basic Analysis Guide - Ansys

Chapter 5: Solution
The following table provides general guidelines you may find useful in selecting which solver to use for a
given problem. MDOF indicates million degrees of freedom.
Table 5.1 Solver Selection Guidelines
Solver
Sparse Direct
Solver
(direct elimination,shared-
memory parallel
solver)
Typical Applications
Ideal Model
Size
When robustness and solution 10,000 to
speed are required (nonlinear ana- 1,000,000
lysis); for linear analysis where iterat- DOFs (works
ive solvers are slow to converge well outside
(especially for ill-conditioned
matrices, such as poorly shaped
elements).
this range).
Memory Use
1 GB/MDOF
(optimal outof-core);
10
GB/MDOF (incore)
PCG Solver Reduces disk I/O requirement relat- 50,000 to 0.3 GB/MDOF
(iterative ive to sparse solver. Best for large 10,000,000+ w/MSAVE,ON;
solver) models with solid elements and fine DOFs
1 GB/MDOF
meshes. Most robust iterative solver
without
in ANSYS
MSAVE
JCG Solver
(iterative
solver)
ICCG Solver
(iterative
solver)
QMR Solver
(iterative
solver)
DPCG Solver
(distributed
solver)
DJCG Solver
(distributed
solver)
AMG Solver
(iterative
solver)
Best for single field problems -
(thermal, magnetics, acoustics, and
multiphysics). Uses a fast but simple
preconditioner with minimal
memory requirement. Not as robust
as PCG solver.
More sophisticated preconditioner
than JCG. Best for more difficult
problems where JCG fails, such as
unsymmetric thermal analyses.
High-frequency electromagnetics.
Same as PCG but runs on distributed
parallel systems.
Same as JCG but runs on distributed
parallel systems. Not as robust as
DPCG or PCG solver.
Good shared memory parallel performance.
Good preconditioner for
ill-conditioned problems where PCG
is slow.
50,000 to
10,000,000+
DOFs
50,000 to
1,000,000+
DOFs
50,000 to
1,000,000+
DOFs
50,000 to
100,000,000+
DOFs
50,000 to
10,000,000+
DOFs
50,000 to
1,000,000+
DOFs
0.5 GB/MDOF
1.5 GB/MDOF
1.5 GB/MDOF
1.5-2.0
GB/MDOF in
total*
0.5 GB/MDOF
1.5-3.0
GB/MDOF in
total*
Distributed Same as sparse solver but runs on 10,000 to 1.5 GB/MDOF
sparse direct distributed parallel systems. This is 5,000,000 on master
solver the default solver for distributed DOFs. Works machine, 1.0
parallel runs. well outside GB/MDOF on
this range. slave machines.
Uses
more total
98
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Disk
(I/O)
Use
10
GB/MDOF
0.5
GB/MDOF
0.5
GB/MDOF
0.5
GB/MDOF
0.5
GB/MDOF
0.5
GB/MDOF
0.5
GB/MDOF
0.5
GB/MDOF
10
GB/MDOF