1: #define PETSCKSP_DLL

 3:  #include private/pcimpl.h

  7: /*@
  8:    PCFactorSetZeroPivot - Sets the size at which smaller pivots are declared to be zero

 10:    Collective on PC
 11:    
 12:    Input Parameters:
 13: +  pc - the preconditioner context
 14: -  zero - all pivots smaller than this will be considered zero

 16:    Options Database Key:
 17: .  -pc_factor_zeropivot <zero> - Sets tolerance for what is considered a zero pivot

 19:    Level: intermediate

 21: .keywords: PC, set, factorization, direct, fill

 23: .seealso: PCFactorSetShiftNonzero(), PCFactorSetShiftPd()
 24: @*/
 25: PetscErrorCode  PCFactorSetZeroPivot(PC pc,PetscReal zero)
 26: {
 27:   PetscErrorCode ierr,(*f)(PC,PetscReal);

 31:   PetscObjectQueryFunction((PetscObject)pc,"PCFactorSetZeroPivot_C",(void (**)(void))&f);
 32:   if (f) {
 33:     (*f)(pc,zero);
 34:   }
 35:   return(0);
 36: }

 40: /*@
 41:    PCFactorSetShiftNonzero - adds this quantity to the diagonal of the matrix during 
 42:      numerical factorization, thus the matrix has nonzero pivots

 44:    Collective on PC
 45:    
 46:    Input Parameters:
 47: +  pc - the preconditioner context
 48: -  shift - amount of shift

 50:    Options Database Key:
 51: .  -pc_factor_shift_nonzero <shift> - Sets shift amount or PETSC_DECIDE for the default

 53:    Note: If 0.0 is given, then no shift is used. If a diagonal element is classified as a zero
 54:          pivot, then the shift is doubled until this is alleviated.

 56:    Level: intermediate

 58: .keywords: PC, set, factorization, direct, fill

 60: .seealso: PCFactorSetZeroPivot(), PCFactorSetShiftPd()
 61: @*/
 62: PetscErrorCode  PCFactorSetShiftNonzero(PC pc,PetscReal shift)
 63: {
 64:   PetscErrorCode ierr,(*f)(PC,PetscReal);

 68:   PetscObjectQueryFunction((PetscObject)pc,"PCFactorSetShiftNonzero_C",(void (**)(void))&f);
 69:   if (f) {
 70:     (*f)(pc,shift);
 71:   }
 72:   return(0);
 73: }

 77: /*@
 78:    PCFactorSetShiftPd - specify whether to use Manteuffel shifting.
 79:    If a matrix factorisation breaks down because of nonpositive pivots,
 80:    adding sufficient identity to the diagonal will remedy this.
 81:    Setting this causes a bisection method to find the minimum shift that
 82:    will lead to a well-defined matrix factor.

 84:    Collective on PC

 86:    Input parameters:
 87: +  pc - the preconditioner context
 88: -  shifting - PETSC_TRUE to set shift else PETSC_FALSE

 90:    Options Database Key:
 91: .  -pc_factor_shift_positive_definite [PETSC_TRUE/PETSC_FALSE] - Activate/Deactivate PCFactorSetShiftPd(); the value
 92:    is optional with PETSC_TRUE being the default

 94:    Level: intermediate

 96: .keywords: PC, indefinite, factorization

 98: .seealso: PCFactorSetZeroPivot(), PCFactorSetShiftNonzero()
 99: @*/
100: PetscErrorCode  PCFactorSetShiftPd(PC pc,PetscTruth shift)
101: {
102:   PetscErrorCode ierr,(*f)(PC,PetscTruth);

106:   PetscObjectQueryFunction((PetscObject)pc,"PCFactorSetShiftPd_C",(void (**)(void))&f);
107:   if (f) {
108:     (*f)(pc,shift);
109:   }
110:   return(0);
111: }