1 #ifdef PETSC_RCS_HEADER 2 static char vcid[] = "$Id: pcnull.c,v 1.14 1998/03/12 23:17:20 bsmith Exp bsmith $"; 3 #endif 4 /* 5 Routines to project vectors out of null spaces. 6 */ 7 8 #include "petsc.h" 9 #include "src/pc/pcimpl.h" /*I "pc.h" I*/ 10 #include "src/sys/nreg.h" 11 #include "sys.h" 12 13 14 #undef __FUNC__ 15 #define __FUNC__ "PCNullSpaceCreate" 16 /*@C 17 PCNullSpaceCreate - Creates a data-structure used to project vectors 18 out of null spaces. 19 20 Input Parameters: 21 . comm - the MPI communicator associated with the object. 22 . has_cnst - if the null spaces contains the constant vector, PETSC_TRUE or PETSC_FALSE 23 . n - number of vectors (excluding constant vector) in null space 24 . vecs - the vectors that span the null space (excluding the constant vector) 25 . these vectors must be orthonormal 26 27 Output Parameter: 28 . SP - the null space context 29 30 Collective on MPI_Comm 31 32 .keywords: PC, Null space 33 @*/ 34 int PCNullSpaceCreate(MPI_Comm comm, int has_cnst, int n, Vec *vecs,PCNullSpace *SP) 35 { 36 PCNullSpace sp; 37 38 PetscFunctionBegin; 39 PetscHeaderCreate(sp,_p_PCNullSpace,int,PCNULLSPACE_COOKIE,0,comm,PCNullSpaceDestroy,0); 40 PLogObjectCreate(sp); 41 PLogObjectMemory(sp,sizeof(struct _p_PCNullSpace)); 42 43 sp->has_cnst = has_cnst; 44 sp->n = n; 45 sp->vecs = vecs; 46 47 *SP = sp; 48 PetscFunctionReturn(0); 49 } 50 51 #undef __FUNC__ 52 #define __FUNC__ "PCNullSpaceDestroy" 53 /*@ 54 PCNullSpaceDestroy - Destroys a data-structure used to project vectors 55 out of null spaces. 56 57 Input Parameter: 58 . SP - the null space context to be destroyed 59 60 Collective on PCNullSpace 61 62 .keywords: PC, Null space 63 @*/ 64 int PCNullSpaceDestroy(PCNullSpace sp) 65 { 66 PetscFunctionBegin; 67 PLogObjectDestroy(sp); 68 PetscHeaderDestroy(sp); 69 PetscFunctionReturn(0); 70 } 71 72 #undef __FUNC__ 73 #define __FUNC__ "PCNullSpaceRemove" 74 /*@ 75 PCNullSpaceRemove - Removes all the components of a null space from a vector. 76 77 Input Parameters: 78 . sp - the null space context 79 . vec - the vector you want the null space removed from 80 81 Collective on PCNullSpace 82 83 .keywords: PC, Null space 84 @*/ 85 int PCNullSpaceRemove(PCNullSpace sp,Vec vec) 86 { 87 Scalar sum; 88 int j, n = sp->n, N,ierr; 89 90 PetscFunctionBegin; 91 if (sp->has_cnst) { 92 ierr = VecSum(vec,&sum); CHKERRQ(ierr); 93 ierr = VecGetSize(vec,&N); CHKERRQ(ierr); 94 sum = -sum/N; 95 ierr = VecShift(&sum,vec); CHKERRQ(ierr); 96 } 97 98 for ( j=0; j<n; j++ ) { 99 ierr = VecDot(vec,sp->vecs[j],&sum);CHKERRQ(ierr); 100 sum = -sum; 101 ierr = VecAYPX(&sum,sp->vecs[j],vec); CHKERRQ(ierr); 102 } 103 104 PetscFunctionReturn(0); 105 } 106