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1999-07-14 20:14:43 +00:00 · 1999-07-14 20:14:43 +00:00 · 3315c72481
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+This README file describes the parameters mechanism for controlling the
+linear solver underlying the finite element interface.
+
+In general, the parameters mechanism accepts a collection of strings
+in the style of the "argc" and "argv" parameters for C programs.
+
+The ISIS++ fei implementation currently accepts the following
+parameter-names, and corresponding values:
+
+parameter-name              value
+---------------------------------
+solver                      cg
+                            cgs
+                            bicgstab
+                            qmr
+                            gmres
+                            fgmres
+                            defgmres
+
+preconditioner              identity    (no preconditioning)
+                            diagonal    (point-wise diagonal scaling)
+                            polynomial  (neumann or least-squares polynomial)
+                            bj          (block-jacobi)
+
+rowScale                    true  (turns on row-wise scaling of the matrix)
+                            false (      off                              )
+
+colScale                    true  (turns on column-wise scaling of the matrix)
+                            false (      off                                 )
+
+
+When the FEI function iterateToSolve is called to launch the iterative
+solver, the user-supplied parameters are also passed on to the solver
+and preconditioner being used. The valid values vary to some extent
+from one solver to another, but all ISIS++ solvers accept the
+parameters:
+
+maxIterations          (value should be some integer)
+tolerance              (some floating-point number, like 1.e-10)
+
+Parameters to particular preconditioners and solvers in ISIS++ include the
+following:
+
+*************************
+Polynomial preconditioner
+
+parameter-name    value
+------------------------
+polyType           1           (Neumann polynomial)
+polyType           2           (Least Squares polynomial)
+polyOrder          <n>         (Order or degree of the polynomial)
+
+***************************
+Block Jacobi preconditioner
+
+parameter-name    value
+------------------------
+blockSize         <n>        (Size of diagonal blocks to be inverted)
+blockType          1         (Non-overlapping blocks)
+blockType          2         (Overlapping blocks, but not across
+                              processor boundaries.)
+
+*************************
+All GMRES solver variants
+
+parameter-name    value
+------------------------
+restart           <n>       (Size of the Krylov subspace between restarts)
+
+
+Note: additional ISIS++ solvers and preconditioners to be added:
+
+Other ISIS++ solvers and preconditioners which are not yet supported
+through the FEI include:
+
+Krylov solvers:
+    CGNE
+    CGNR
+
+Preconditioners:
+    CGNE_Diagonal
+    CGNE_BlockJacobi
+    CGNE_Polynomial
+    CGNR_Polynomial
+    SPAI  (Sparse Approximate Inverse)
+          (SPAI accepts several control parameters, to be
+           documented here later.)
+
+These will be enabled in an upcoming fei-isis code relese.
+
+Additionally, if preconditioners from CASC (LLNL) are (separately)
+installed, we will be able to turn on recognition of these preconditioners:
+
+      SAILS
+      PILUT
+      AMGe
+
+(the SAILS preconditioner is actually installed as part of the ISIS++ 
+distribution, and can be enabled any time.)
+
+
+
+(I'm putting together some actual FEI usage documentation, but it isn't
+available yet.)
+
+Alan Williams (william@ca.sandia.gov)
+