Actual source code: cgtype.c

petsc-3.5.2 2014-09-08
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  2: #include <../src/ksp/ksp/impls/cg/cgimpl.h>       /*I "petscksp.h" I*/

  6: /*@
  7:     KSPCGSetType - Sets the variant of the conjugate gradient method to
  8:     use for solving a linear system with a complex coefficient matrix.
  9:     This option is irrelevant when solving a real system.

 11:     Logically Collective on KSP

 13:     Input Parameters:
 14: +   ksp - the iterative context
 15: -   type - the variant of CG to use, one of
 16: .vb
 17:       KSP_CG_HERMITIAN - complex, Hermitian matrix (default)
 18:       KSP_CG_SYMMETRIC - complex, symmetric matrix
 19: .ve

 21:     Level: intermediate

 23:     Options Database Keys:
 24: +   -ksp_cg_Hermitian - Indicates Hermitian matrix
 25: -   -ksp_cg_symmetric - Indicates symmetric matrix

 27:     Note:
 28:     By default, the matrix is assumed to be complex, Hermitian.

 30: .keywords: CG, conjugate gradient, Hermitian, symmetric, set, type
 31: @*/
 32: PetscErrorCode  KSPCGSetType(KSP ksp,KSPCGType type)
 33: {

 38:   PetscTryMethod(ksp,"KSPCGSetType_C",(KSP,KSPCGType),(ksp,type));
 39:   return(0);
 40: }

 44: /*@
 45:     KSPCGUseSingleReduction - Merge the two inner products needed in CG into a single MPI_Allreduce() call.

 47:     Logically Collective on KSP

 49:     Input Parameters:
 50: +   ksp - the iterative context
 51: -   flg - turn on or off the single reduction

 53:     Options Database:
 54: .   -ksp_cg_single_reduction

 56:     Level: intermediate

 58:      The algorithm used in this case is described as Method 1 in Lapack Working Note 56, "Conjugate Gradient Algorithms with Reduced Synchronization Overhead
 59:      Distributed Memory Multiprocessors", by E. F. D'Azevedo, V. L. Eijkhout, and C. H. Romine, December 3, 1999. V. Eijkhout creates the algorithm
 60:      initially to Chronopoulos and Gear.

 62:      It requires two extra work vectors than the conventional implementation in PETSc.

 64:      See also KSPPIPECG, KSPPIPECR, and KSPGROPPCG that use non-blocking reductions.

 66: .keywords: CG, conjugate gradient, Hermitian, symmetric, set, type, KSPPGMRES
 67: @*/
 68: PetscErrorCode  KSPCGUseSingleReduction(KSP ksp,PetscBool flg)
 69: {

 75:   PetscTryMethod(ksp,"KSPCGUseSingleReduction_C",(KSP,PetscBool),(ksp,flg));
 76:   return(0);
 77: }