Actual source code: matnull.c
1: #define PETSCMAT_DLL
3: /*
4: Routines to project vectors out of null spaces.
5: */
7: #include include/private/matimpl.h
8: #include petscsys.h
10: PetscCookie MAT_NULLSPACE_COOKIE = 0;
14: /*@C
15: MatNullSpaceSetFunction - set a function that removes a null space from a vector
16: out of null spaces.
18: Collective on MatNullSpace
20: Input Parameters:
21: + sp - the null space object
22: . rem - the function that removes the null space
23: - ctx - context for the remove function
25: Level: advanced
27: .keywords: PC, null space, create
29: .seealso: MatNullSpaceDestroy(), MatNullSpaceRemove(), KSPSetNullSpace(), MatNullSpace, MatNullSpaceCreate()
30: @*/
31: PetscErrorCode MatNullSpaceSetFunction(MatNullSpace sp, PetscErrorCode (*rem)(Vec,void*),void *ctx)
32: {
35: sp->remove = rem;
36: sp->rmctx = ctx;
37: return(0);
38: }
42: /*@
43: MatNullSpaceCreate - Creates a data structure used to project vectors
44: out of null spaces.
46: Collective on MPI_Comm
48: Input Parameters:
49: + comm - the MPI communicator associated with the object
50: . has_cnst - PETSC_TRUE if the null space contains the constant vector; otherwise PETSC_FALSE
51: . n - number of vectors (excluding constant vector) in null space
52: - vecs - the vectors that span the null space (excluding the constant vector);
53: these vectors must be orthonormal. These vectors are NOT copied, so do not change them
54: after this call. You should free the array that you pass in.
56: Output Parameter:
57: . SP - the null space context
59: Level: advanced
61: Users manual sections:
62: . Section 4.15 Solving Singular Systems
64: .keywords: PC, null space, create
66: .seealso: MatNullSpaceDestroy(), MatNullSpaceRemove(), KSPSetNullSpace(), MatNullSpace, MatNullSpaceSetFunction()
67: @*/
68: PetscErrorCode MatNullSpaceCreate(MPI_Comm comm,PetscTruth has_cnst,PetscInt n,const Vec vecs[],MatNullSpace *SP)
69: {
70: MatNullSpace sp;
72: PetscInt i;
75: if (n < 0) SETERRQ1(PETSC_ERR_ARG_OUTOFRANGE,"Number of vectors (given %D) cannot be negative",n);
79:
80: *SP = PETSC_NULL;
81: #ifndef PETSC_USE_DYNAMIC_LIBRARIES
82: MatInitializePackage(PETSC_NULL);
83: #endif
85: PetscHeaderCreate(sp,_p_MatNullSpace,int,MAT_NULLSPACE_COOKIE,0,"MatNullSpace",comm,MatNullSpaceDestroy,0);
86: PetscLogObjectMemory(sp,sizeof(struct _p_MatNullSpace));
88: sp->has_cnst = has_cnst;
89: sp->n = n;
90: sp->vecs = 0;
91: sp->alpha = 0;
92: sp->vec = 0;
93: sp->remove = 0;
94: sp->rmctx = 0;
96: if (n) {
97: PetscMalloc(n*sizeof(Vec),&sp->vecs);
98: PetscMalloc(n*sizeof(PetscScalar),&sp->alpha);
99: PetscLogObjectMemory(sp,n*(sizeof(Vec)+sizeof(PetscScalar)));
100: for (i=0; i<n; i++) {
101: PetscObjectReference((PetscObject)vecs[i]);
102: sp->vecs[i] = vecs[i];
103: }
104: }
106: *SP = sp;
107: return(0);
108: }
112: /*@
113: MatNullSpaceDestroy - Destroys a data structure used to project vectors
114: out of null spaces.
116: Collective on MatNullSpace
118: Input Parameter:
119: . sp - the null space context to be destroyed
121: Level: advanced
123: .keywords: PC, null space, destroy
125: .seealso: MatNullSpaceCreate(), MatNullSpaceRemove(), MatNullSpaceSetFunction()
126: @*/
127: PetscErrorCode MatNullSpaceDestroy(MatNullSpace sp)
128: {
133: if (--sp->refct > 0) return(0);
135: if (sp->vec) { VecDestroy(sp->vec); }
136: if (sp->vecs) { VecDestroyVecs(sp->vecs,sp->n); }
137: PetscFree(sp->alpha);
138: PetscHeaderDestroy(sp);
139: return(0);
140: }
144: /*@
145: MatNullSpaceRemove - Removes all the components of a null space from a vector.
147: Collective on MatNullSpace
149: Input Parameters:
150: + sp - the null space context
151: . vec - the vector from which the null space is to be removed
152: - out - if this is requested (not PETSC_NULL) then this is a vector with the null space removed otherwise
153: the removal is done in-place (in vec)
155: Note: The user is not responsible for the vector returned and should not destroy it.
157: Level: advanced
159: .keywords: PC, null space, remove
161: .seealso: MatNullSpaceCreate(), MatNullSpaceDestroy(), MatNullSpaceSetFunction()
162: @*/
163: PetscErrorCode MatNullSpaceRemove(MatNullSpace sp,Vec vec,Vec *out)
164: {
165: PetscScalar sum;
166: PetscInt i,N;
173: if (out) {
175: if (!sp->vec) {
176: VecDuplicate(vec,&sp->vec);
177: PetscLogObjectParent(sp,sp->vec);
178: }
179: VecCopy(vec,sp->vec);
180: vec = *out = sp->vec;
181: }
182:
183: if (sp->has_cnst) {
184: VecGetSize(vec,&N);
185: if (N > 0) {
186: VecSum(vec,&sum);
187: sum = sum/(-1.0*N);
188: VecShift(vec,sum);
189: }
190: }
191:
192: if (sp->n) {
193: VecMDot(vec,sp->n,sp->vecs,sp->alpha);
194: for (i=0; i<sp->n; i++) sp->alpha[i] = -sp->alpha[i];
195: VecMAXPY(vec,sp->n,sp->alpha,sp->vecs);
196: }
198: if (sp->remove){
199: (*sp->remove)(vec,sp->rmctx);
200: }
201: return(0);
202: }
206: /*@
207: MatNullSpaceTest - Tests if the claimed null space is really a
208: null space of a matrix
210: Collective on MatNullSpace
212: Input Parameters:
213: + sp - the null space context
214: - mat - the matrix
216: Level: advanced
218: .keywords: PC, null space, remove
220: .seealso: MatNullSpaceCreate(), MatNullSpaceDestroy(), MatNullSpaceSetFunction()
221: @*/
222: PetscErrorCode MatNullSpaceTest(MatNullSpace sp,Mat mat)
223: {
224: PetscScalar sum;
225: PetscReal nrm;
226: PetscInt j,n,N,m;
228: Vec l,r;
229: PetscTruth flg1,flg2;
230: PetscViewer viewer;
235: n = sp->n;
236: PetscOptionsHasName(PETSC_NULL,"-mat_null_space_test_view",&flg1);
237: PetscOptionsHasName(PETSC_NULL,"-mat_null_space_test_view_draw",&flg2);
239: if (!sp->vec) {
240: if (n) {
241: VecDuplicate(sp->vecs[0],&sp->vec);
242: } else {
243: MatGetLocalSize(mat,&m,PETSC_NULL);
244: VecCreateMPI(sp->comm,m,PETSC_DETERMINE,&sp->vec);
245: }
246: }
247: l = sp->vec;
249: PetscViewerASCIIGetStdout(sp->comm,&viewer);
250: if (sp->has_cnst) {
251: VecDuplicate(l,&r);
252: VecGetSize(l,&N);
253: sum = 1.0/N;
254: VecSet(l,sum);
255: MatMult(mat,l,r);
256: VecNorm(r,NORM_2,&nrm);
257: if (nrm < 1.e-7) {PetscPrintf(sp->comm,"Constants are likely null vector");}
258: else {PetscPrintf(sp->comm,"Constants are unlikely null vector ");}
259: PetscPrintf(sp->comm,"|| A * 1 || = %G\n",nrm);
260: if (nrm > 1.e-7 && flg1) {VecView(r,viewer);}
261: if (nrm > 1.e-7 && flg2) {VecView(r,viewer);}
262: VecDestroy(r);
263: }
265: for (j=0; j<n; j++) {
266: (*mat->ops->mult)(mat,sp->vecs[j],l);
267: VecNorm(l,NORM_2,&nrm);
268: if (nrm < 1.e-7) {PetscPrintf(sp->comm,"Null vector %D is likely null vector",j);}
269: else {PetscPrintf(sp->comm,"Null vector %D unlikely null vector ",j);}
270: PetscPrintf(sp->comm,"|| A * v[%D] || = %G\n",j,nrm);
271: if (nrm > 1.e-7 && flg1) {VecView(l,viewer);}
272: if (nrm > 1.e-7 && flg2) {VecView(l,viewer);}
273: }
275: if (sp->remove){
276: SETERRQ(PETSC_ERR_SUP,"Cannot test a null space provided as a function with MatNullSpaceSetFunction()");
277: }
278:
279: return(0);
280: }