/*@
ISCreateStride - Creates a data structure for an index set
containing a list of evenly spaced integers.
Collective on MPI_Comm
Input Parameters:
+ comm - the MPI communicator
. n - the length of the locally owned portion of the index set
. first - the first element of the locally owned portion of the index set
- step - the change to the next index
Output Parameter:
. is - the new index set
Notes:
When the communicator is not MPI_COMM_SELF, the operations on IS are NOT
conceptually the same as MPI_Group operations. The IS are the
distributed sets of indices and thus certain operations on them are collective.
Level: beginner
Concepts: IS^stride
Concepts: index sets^stride
Concepts: stride^index set
.seealso: ISCreateGeneral(), ISCreateBlock(), ISAllGather()
@*/
PetscErrorCode ISCreateStride(MPI_Comm comm,PetscInt n,PetscInt first,PetscInt step,IS *is)
{
PetscErrorCode ierr;
PetscFunctionBegin;
ierr = ISCreate(comm,is);CHKERRQ(ierr);
ierr = ISSetType(*is,ISSTRIDE);CHKERRQ(ierr);
ierr = ISStrideSetStride(*is,n,first,step);CHKERRQ(ierr);
PetscFunctionReturn(0);
}
-m # : the size of the vectors\n \
-n # : the numer of indices (with n<=m)\n \
-toFirst # : the starting index of the output vector for strided scatters\n \
-toStep # : the step size into the output vector for strided scatters\n \
-fromFirst # : the starting index of the input vector for strided scatters\n\
-fromStep # : the step size into the input vector for strided scatters\n\n";
int main(int argc, char * argv[]) {
Vec X,Y;
PetscInt m,n,i,n1,n2;
PetscInt toFirst,toStep,fromFirst,fromStep;
PetscInt *idx,*idy;
PetscBool flg;
IS toISStrided,fromISStrided,toISGeneral,fromISGeneral;
VecScatter vscatSStoSS,vscatSStoSG,vscatSGtoSS,vscatSGtoSG;
ScatterMode mode;
InsertMode addv;
PetscErrorCode ierr;
ierr = PetscInitialize(&argc,&argv,0,help);CHKERRQ(ierr);
ierr = PetscOptionsGetInt(NULL,"-m",&m,&flg);CHKERRQ(ierr);
if (!flg) m = 100;
ierr = PetscOptionsGetInt(NULL,"-n",&n,&flg);CHKERRQ(ierr);
if (!flg) n = 30;
ierr = PetscOptionsGetInt(NULL,"-toFirst",&toFirst,&flg);CHKERRQ(ierr);
if (!flg) toFirst = 3;
ierr = PetscOptionsGetInt(NULL,"-toStep",&toStep,&flg);CHKERRQ(ierr);
if (!flg) toStep = 3;
ierr = PetscOptionsGetInt(NULL,"-fromFirst",&fromFirst,&flg);CHKERRQ(ierr);
if (!flg) fromFirst = 2;
ierr = PetscOptionsGetInt(NULL,"-fromStep",&fromStep,&flg);CHKERRQ(ierr);
if (!flg) fromStep = 2;
if (n>m) {
PetscPrintf(PETSC_COMM_WORLD,"The vector sizes are %d. The number of elements being scattered is %d\n",m,n);CHKERRQ(ierr);
PetscPrintf(PETSC_COMM_WORLD,"Adjust the parameters such that m>=n\n");CHKERRQ(ierr);
} else if (toFirst+(n-1)*toStep >=m) {
PetscPrintf(PETSC_COMM_WORLD,"The vector sizes are %d. The number of elements being scattered is %d\n",m,n);CHKERRQ(ierr);
PetscPrintf(PETSC_COMM_WORLD,"For the Strided Scatter, toFirst=%d and toStep=%d.\n",toFirst,toStep);CHKERRQ(ierr);
PetscPrintf(PETSC_COMM_WORLD,"This produces an index (toFirst+(n-1)*toStep)>=m\n");CHKERRQ(ierr);
PetscPrintf(PETSC_COMM_WORLD,"Adjust the parameterrs accordingly with -m, -n, -toFirst, or -toStep\n");CHKERRQ(ierr);
} else if (fromFirst+(n-1)*fromStep>=m) {
PetscPrintf(PETSC_COMM_WORLD,"The vector sizes are %d. The number of elements being scattered is %d\n",m,n);CHKERRQ(ierr);
PetscPrintf(PETSC_COMM_WORLD,"For the Strided Scatter, fromFirst=%d and fromStep=%d.\n",fromFirst,toStep);CHKERRQ(ierr);
PetscPrintf(PETSC_COMM_WORLD,"This produces an index (fromFirst+(n-1)*fromStep)>=m\n");CHKERRQ(ierr);
PetscPrintf(PETSC_COMM_WORLD,"Adjust the parameterrs accordingly with -m, -n, -fromFirst, or -fromStep\n");CHKERRQ(ierr);
} else {
PetscPrintf(PETSC_COMM_WORLD,"m=%d\tn=%d\tfromFirst=%d\tfromStep=%d\ttoFirst=%d\ttoStep=%d\n",m,n,fromFirst,fromStep,toFirst,toStep);CHKERRQ(ierr);
PetscPrintf(PETSC_COMM_WORLD,"fromFirst+(n-1)*fromStep=%d\ttoFirst+(n-1)*toStep=%d\n",fromFirst+(n-1)*fromStep,toFirst+(n-1)*toStep);CHKERRQ(ierr);
/* Build the vectors */
ierr = VecCreate(PETSC_COMM_WORLD,&Y);CHKERRQ(ierr);
ierr = VecSetSizes(Y,m,PETSC_DECIDE);CHKERRQ(ierr);
ierr = VecCreate(PETSC_COMM_WORLD,&X);CHKERRQ(ierr);
ierr = VecSetSizes(X,m,PETSC_DECIDE);CHKERRQ(ierr);
ierr = VecSetFromOptions(Y);CHKERRQ(ierr);
ierr = VecSetFromOptions(X);CHKERRQ(ierr);
ierr = VecSet(X,2.0);CHKERRQ(ierr);
ierr = VecSet(Y,1.0);CHKERRQ(ierr);
/* Build the strided index sets */
ierr = ISCreate(PETSC_COMM_WORLD,&toISStrided);CHKERRQ(ierr);
ierr = ISCreate(PETSC_COMM_WORLD,&fromISStrided);CHKERRQ(ierr);
ierr = ISSetType(toISStrided, ISSTRIDE);CHKERRQ(ierr);
ierr = ISSetType(fromISStrided, ISSTRIDE);CHKERRQ(ierr);
ierr = ISStrideSetStride(fromISStrided,n,fromFirst,fromStep);CHKERRQ(ierr);
ierr = ISStrideSetStride(toISStrided,n,toFirst,toStep);CHKERRQ(ierr);
/* Build the general index sets */
ierr = PetscMalloc1(n,&idx);CHKERRQ(ierr);
ierr = PetscMalloc1(n,&idy);CHKERRQ(ierr);
for (i=0; i<n; i++) {
idx[i] = i % m;
idy[i] = (i+m) % m;
}
n1 = n;
n2 = n;
ierr = PetscSortRemoveDupsInt(&n1,idx);CHKERRQ(ierr);
ierr = PetscSortRemoveDupsInt(&n2,idy);CHKERRQ(ierr);
ierr = ISCreateGeneral(PETSC_COMM_WORLD,n1,idx,PETSC_COPY_VALUES,&toISGeneral);CHKERRQ(ierr);
ierr = ISCreateGeneral(PETSC_COMM_WORLD,n2,idy,PETSC_COPY_VALUES,&fromISGeneral);CHKERRQ(ierr);
/* set the mode and the insert/add parameter */
mode = SCATTER_FORWARD;
addv = ADD_VALUES;
/* VecScatter : Seq Strided to Seq Strided */
ierr = VecScatterCreate(X,fromISStrided,Y,toISStrided,&vscatSStoSS);CHKERRQ(ierr);
ierr = VecScatterBegin(vscatSStoSS,X,Y,addv,mode);CHKERRQ(ierr);
ierr = VecScatterEnd(vscatSStoSS,X,Y,addv,mode);CHKERRQ(ierr);
ierr = VecScatterDestroy(&vscatSStoSS);CHKERRQ(ierr);
/* VecScatter : Seq General to Seq Strided */
ierr = VecScatterCreate(Y,fromISGeneral,X,toISStrided,&vscatSGtoSS);CHKERRQ(ierr);
ierr = VecScatterBegin(vscatSGtoSS,Y,X,addv,mode);CHKERRQ(ierr);
ierr = VecScatterEnd(vscatSGtoSS,Y,X,addv,mode);CHKERRQ(ierr);
ierr = VecScatterDestroy(&vscatSGtoSS);CHKERRQ(ierr);
/* VecScatter : Seq General to Seq General */
ierr = VecScatterCreate(X,fromISGeneral,Y,toISGeneral,&vscatSGtoSG);CHKERRQ(ierr);
ierr = VecScatterBegin(vscatSGtoSG,X,Y,addv,mode);CHKERRQ(ierr);
ierr = VecScatterEnd(vscatSGtoSG,X,Y,addv,mode);CHKERRQ(ierr);
ierr = VecScatterDestroy(&vscatSGtoSG);CHKERRQ(ierr);
/* VecScatter : Seq Strided to Seq General */
ierr = VecScatterCreate(Y,fromISStrided,X,toISGeneral,&vscatSStoSG);CHKERRQ(ierr);
ierr = VecScatterBegin(vscatSStoSG,Y,X,addv,mode);CHKERRQ(ierr);
ierr = VecScatterEnd(vscatSStoSG,Y,X,addv,mode);CHKERRQ(ierr);
ierr = VecScatterDestroy(&vscatSStoSG);CHKERRQ(ierr);
/* view the results */
ierr = VecView(Y,PETSC_VIEWER_STDOUT_WORLD);CHKERRQ(ierr);
/* Cleanup */
ierr = VecDestroy(&X);CHKERRQ(ierr);
ierr = VecDestroy(&Y);CHKERRQ(ierr);
ierr = ISDestroy(&toISStrided);CHKERRQ(ierr);
ierr = ISDestroy(&fromISStrided);CHKERRQ(ierr);
ierr = ISDestroy(&toISGeneral);CHKERRQ(ierr);
ierr = ISDestroy(&fromISGeneral);CHKERRQ(ierr);
ierr = PetscFree(idx);CHKERRQ(ierr);
ierr = PetscFree(idy);CHKERRQ(ierr);
}
PetscFinalize();
return 0;
}
