1 /*$Id: pcnull.c,v 1.31 2000/05/05 22:16:59 balay Exp bsmith $*/ 2 /* 3 Routines to project vectors out of null spaces. 4 */ 5 6 #include "src/mat/matimpl.h" /*I "petscmat.h" I*/ 7 #include "petscsys.h" 8 9 #undef __FUNC__ 10 #define __FUNC__ /*<a name=""></a>*/"MatNullSpaceCreate" 11 /*@C 12 MatNullSpaceCreate - Creates a data structure used to project vectors 13 out of null spaces. 14 15 Collective on MPI_Comm 16 17 Input Parameters: 18 + comm - the MPI communicator associated with the object 19 . has_cnst - PETSC_TRUE if the null space contains the constant vector; otherwise PETSC_FALSE 20 . n - number of vectors (excluding constant vector) in null space 21 - vecs - the vectors that span the null space (excluding the constant vector); 22 these vectors must be orthonormal 23 24 Output Parameter: 25 . SP - the null space context 26 27 Level: advanced 28 29 .keywords: PC, null space, create 30 31 .seealso: MatNullSpaceDestroy(), MatNullSpaceRemove() 32 @*/ 33 int MatNullSpaceCreate(MPI_Comm comm,int has_cnst,int n,Vec *vecs,MatNullSpace *SP) 34 { 35 MatNullSpace sp; 36 37 PetscFunctionBegin; 38 PetscHeaderCreate(sp,_p_MatNullSpace,int,MATNULLSPACE_COOKIE,0,"MatNullSpace",comm,MatNullSpaceDestroy,0); 39 PLogObjectCreate(sp); 40 PLogObjectMemory(sp,sizeof(struct _p_MatNullSpace)); 41 42 sp->has_cnst = has_cnst; 43 sp->n = n; 44 sp->vecs = vecs; 45 sp->vec = PETSC_NULL; 46 47 *SP = sp; 48 PetscFunctionReturn(0); 49 } 50 51 #undef __FUNC__ 52 #define __FUNC__ /*<a name=""></a>*/"MatNullSpaceDestroy" 53 /*@ 54 MatNullSpaceDestroy - Destroys a data structure used to project vectors 55 out of null spaces. 56 57 Collective on MatNullSpace 58 59 Input Parameter: 60 . sp - the null space context to be destroyed 61 62 Level: advanced 63 64 .keywords: PC, null space, destroy 65 66 .seealso: MatNullSpaceCreate(), MatNullSpaceRemove() 67 @*/ 68 int MatNullSpaceDestroy(MatNullSpace sp) 69 { 70 int ierr; 71 72 PetscFunctionBegin; 73 if (--sp->refct > 0) PetscFunctionReturn(0); 74 75 if (sp->vec) {ierr = VecDestroy(sp->vec);CHKERRQ(ierr);} 76 77 PLogObjectDestroy(sp); 78 PetscHeaderDestroy(sp); 79 PetscFunctionReturn(0); 80 } 81 82 #undef __FUNC__ 83 #define __FUNC__ /*<a name=""></a>*/"MatNullSpaceRemove" 84 /*@ 85 MatNullSpaceRemove - Removes all the components of a null space from a vector. 86 87 Collective on MatNullSpace 88 89 Input Parameters: 90 + sp - the null space context 91 - vec - the vector from which the null space is to be removed 92 93 Level: advanced 94 95 .keywords: PC, null space, remove 96 97 .seealso: MatNullSpaceCreate(), MatNullSpaceDestroy() 98 @*/ 99 int MatNullSpaceRemove(MatNullSpace sp,Vec vec,Vec *out) 100 { 101 Scalar sum; 102 int j,n = sp->n,N,ierr; 103 Vec l = vec; 104 105 PetscFunctionBegin; 106 if (out) { 107 if (!sp->vec) { 108 ierr = VecDuplicate(vec,&sp->vec);CHKERRQ(ierr); 109 } 110 *out = sp->vec; 111 ierr = VecCopy(vec,*out);CHKERRQ(ierr); 112 l = *out; 113 } 114 115 if (sp->has_cnst) { 116 ierr = VecSum(l,&sum);CHKERRQ(ierr); 117 ierr = VecGetSize(l,&N);CHKERRQ(ierr); 118 sum = sum/(-1.0*N); 119 ierr = VecShift(&sum,l);CHKERRQ(ierr); 120 } 121 122 for (j=0; j<n; j++) { 123 ierr = VecDot(l,sp->vecs[j],&sum);CHKERRQ(ierr); 124 sum = -sum; 125 ierr = VecAXPY(&sum,sp->vecs[j],l);CHKERRQ(ierr); 126 } 127 128 PetscFunctionReturn(0); 129 } 130