[petsc-users] I write the following program, it can converge with 4 processor, but can not converge with 2 , or 3 processor. Could you help me out

Matthew Knepley knepley at gmail.com
Fri Aug 16 06:54:01 CDT 2013 

On Fri, Aug 16, 2013 at 6:13 AM, 丁老师 <ztdepyahoo at 163.com> wrote:

Its common for iterative solvers to converge differently for different PC.
You are using block Jacobi-ILU
which is different for different numbers of processes.

   Matt

/* Program usage:  mpiexec ex1 [-help] [all PETSc options] */
>
> static char help[] = "Basic vector routines.\n\n";
>
>
> #include "petscksp.h"
> #include "petscvec.h"
>
>
>
> int main(int argc,char **argv)
> {
>   int N=16;
>
>   int MyRank;
>
>    Mat A;
>    PC Pc;
>    KSP ksp;
>    Vec b,x;
>
>  PetscInitialize(&argc,&argv,(char*)0,help);
>   MPI_Comm_rank(MPI_COMM_WORLD,&MyRank);
>
>   MatCreate(PETSC_COMM_WORLD,&A);
>   MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,N,N);
>   MatSetFromOptions(A);
>   MatMPIAIJSetPreallocation(A,5,PETSC_NULL,5,PETSC_NULL);
>
>   VecCreate(PETSC_COMM_WORLD,&b);
>   VecSetSizes(b,PETSC_DECIDE,N);
>   VecSetFromOptions(b);
>   VecDuplicate(b,&x);
> &n bsp;
>   int row=0;
>   int* col3;
>   int* col4;
>   int* col5;
>   PetscMalloc(3*sizeof(PetscInt),&col3);
>   PetscMalloc(4*sizeof(PetscInt),&col4);
>   PetscMalloc(5*sizeof(PetscInt),&col5);
>
>   col3[0]=0;  col3[1]=1;  col3[2]=4;
>  double
> value3[3]={2.2916666666666665e+00,-1.1458333333333333e+00,-1.1458333333333333e+00};
>  MatSetValues(A,1,&row,3,col3,value3,INSERT_VALUES);
>
>  row=1;
>  col4[0]=0;  col4[1]=1;  col4[2]=2; col4[3]=5;
>  double
> value4[4]={-1.1458333333333333e+00,3.8020833333333330e+00,-1.2500000000000000e+00
> ,-1.4062500000000000e+00};
>   MatSetValues(A,1,&row,4,col4,value4,INSERT_VALUES);
>
>
>   row=2;
>  col4[0]=1;  col4[1]=2;  col4[2]=3; col4[3]=6;
>  value4[0]=-1.2500000000000000e+00;
>  value4[1]=3.8020833333333330e+00;
>  value4[2]=-1.1458333333333333e+00 ;
> &n bsp;value4[3]=-1.4062500000000000e+00;
>   MatSetValues(A,1,&row,4,col4,value4,INSERT_VALUES);
>
>
>    row=3;
>   col3[0]=2;  col3[1]=3;  col3[2]=7;
>  value3[0]=-1.1458333333333333e+00;
>  value3[1]=2.2916666666666665e+00;
>  value3[2]=-1.1458333333333333e+00;
>  MatSetValues(A,1,&row,3,col3,value3,INSERT_VALUES);
>
>
>   row=4;
>  col4[0]=0;  col4[1]=4;  col4[2]=5; col4[3]=8;
>  value4[0]=-1.1458333333333333e+00;
>  value4[1]=3.8020833333333330e+00;
>  value4[2]=-1.4062500000000000e+00;
>  value4[3]=-1.2500000000000000e+00;
>   MatSetValues(A,1,&row,4,col4,value4,INSERT_VALUES);
>
>    row=5;
>  col5[0]=1;  col5[1]=4;  col5[2]=5; col5[3]=6; col5[4]=9;
>  double value5[5];
>  value5[0]=-1.4062500000000000e+00;
>  value5[1]=-1.4062500000000000e+00;
>  value5[2]=5 .9375000000000000e+00;
>  value5[3]=-1.5625000000000000e+00 ;
>  value5[4]=-1.5625000000000000e+00 ;
>   MatSetValues(A,1,&row,5,col5,value5,INSERT_VALUES);
>
>
>
>   row=6;
>  col5[0]=2;  col5[1]=5;  col5[2]=6; col5[3]=7; col5[4]=10;
>  value5[0]=-1.4062500000000000e+00;
>  value5[1]=-1.5625000000000000e+00;
>  value5[2]=5.9375000000000000e+00;
>  value5[3]=-1.4062500000000000e+00 ;
>  value5[4]=-1.5625000000000000e+00 ;
>   MatSetValues(A,1,&row,5,col5,value5,INSERT_VALUES);
>
>   row=7;
>  col4[0]=3;  col4[1]=6;  col4[2]=7; col4[3]=11;
>  value4[0]=-1.1458333333333333e+00;
>  value4[1]=-1.4062500000000000e+00;
>  value4[2]=3.8020833333333330e+00;
>  value4[3]=-1.2500000000000000e+00;
>   MatSetValues(A,1,&row,4,col4,value4,INSERT_VALUES);
>
>   row=8;
>   col4[0]=4;  col4[1]=8;  col4[2]=9; col4[3]=12;
>  value4[0]=-1.2500000000000000e+00;
>  value4[1]=3.8020833333333330e+00;
>  value4[2]=-1.4062500000000000e+00;
>  value4[3]=-1.1458333333333333e+00;
>   MatSetValues(A,1,&row,4,col4,value4,INSERT_VALUES);
>
>
>    row=9;
>  col5[0]=5;  col5[1]=8;  col5[2]=9; col5[3]=10; col5[4]=13;
>  value5[0]=-1.5625000000000000e+00;
>  value5[1]=-1.4062500000000000e+00;
>  value5[2]=5.9375000000000000e+00;
>  value5[3]=-1.5625000000000000e+00 ;
>  value5[4]= -1.4062500000000000e+00;
>   MatSetValues(A,1,&row,5,col5,value5,INSERT_VALUES);
>
>      row=10;
>  col5[0]=6;  col5[1]=9;  col5[2]=10; col5[3]=11; col5[4]=14;
>  value5[0]=-1.5625000000000000e+00;
>  value5[1]=-1.5625000000000000e+00;
>  value5[2]=5.93750000000000 00e+00;
>  value5[3]=-1.4062500000000000e+00 ;
>  value5[4]= -1.4062500000000000e+00;
>   MatSetValues(A,1,&row,5,col5,value5,INSERT_VALUES);
>
>
>   row=11;
>  col4[0]=7;  col4[1]=10;  col4[2]=11; col4[3]=15;
>  value4[0]=-1.2500000000000000e+00;
>  value4[1]=-1.4062500000000000e+00;
>  value4[2]=3.8020833333333330e+00;
>  value4[3]=-1.1458333333333333e+00;
>   MatSetValues(A,1,&row,4,col4,value4,INSERT_VALUES);
>
>
>
>
>     row=12;
>   col3[0]=8;  col3[1]=12;  col3[2]=13;
>  value3[0]=-1.1458333333333333e+00;
>  value3[1]=2.2916666666666665e+00;
>  value3[2]=-1.1458333333333333e+00;
>  MatSetValues(A,1,&row,3,col3,value3,INSERT_VALUES);
>
>
>    row=13;
>  col4[0]=9;  col4[1]=12;  col4[2]=13; col4[3]= 14;
>  value4[0]=-1.4062500000000000e+00;
>  value4[1]=-1.1458333333333333e+00;
>  value4[2]=3.8020833333333330e+00;
>  value4[3]=-1.2500000000000000e+00;
>   MatSetValues(A,1,&row,4,col4,value4,INSERT_VALUES);
>
>
>    row=14;
>  col4[0]=10;  col4[1]=13;  col4[2]=14; col4[3]=15;
>  value4[0]=-1.4062500000000000e+00;
>  value4[1]=-1.2500000000000000e+00;
>  value4[2]=3.8020833333333330e+00;
>  value4[3]=-1.1458333333333333e+00;
>   MatSetValues(A,1,&row,4,col4,value4,INSERT_VALUES);
>
>
>
>      row=15;
>   col3[0]=11;  col3[1]=14;  col3[2]=15;
>  value3[0]=-1.1458333333333333e+00;
>  value3[1]=-1.1458333333333333e+00;
>  value3[2]=2.2916666666666665e+00;
>  MatSetValues(A,1,&row,3,col3,value3,INSERT_VALUES);
>
>
> &n bsp;
>   MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
>   MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
>
> //  MatView(A,PETSC_VIEWER_STDOUT_WORLD);
>
>
>
>   double val[16]={-7.6233779415782715e-04,
> -3.0457072596705860e-04,
> 3.0457072596705860e-04,
> 7.6233779415782715e-04,
> -4.4764543813290442e-03,
> -1.6196451741044846e-03,
> 1.6196451741044846e-03,
> 4.4764543813290442e-03,
> -1.9333475373837013e-02,
> -5.4815619458573189e-03,
> 5.4815619458573189e-03,
> 1.9333475373837013e-02,
> -8.4153777598326651e-02,
> -1.2883385353962010e-02,
> 1.2883385353962010e-02,
> 8.4153777598326651e-02};
>
> int* col16;
>   PetscMalloc(16*sizeof(PetscInt),&col16);
>  for(int i=0;i<16;i++)
>   col16[i]=i;
>
> VecSetValues(b,16,col16,val,INSERT_VALUES);
>     VecAssemblyBegin(b);
>     VecAssemblyEnd(b);
> //
>  &nbs p;   VecView(b,PETSC_VIEWER_STDOUT_WORLD);
>
>
>   KSPCreate(PETSC_COMM_WORLD,&ksp);
>   KSPSetOperators(ksp,A,A,SAME_NONZERO_PATTERN);
>   KSPSetOperators(ksp,A,A,SAME_PRECONDITIONER);
>   KSPSetInitialGuessNonzero(ksp,PETSC_FALSE);
>
>   KSPSetType(ksp,KSPBCGS);
>  //  KSPSetType(ksp,KSPLSQR);
>  //  KSPSetType(ksp,KSPFGMRES);
>  // KSPSetType(ksp,KSPDGMRES);
> //KSPSetType(ksp,KSPTCQMR);
>  // KSPSetType(ksp,KSPPREONLY);
>
>   //KSPGetPC(ksp,&Pc);
>  // PCSetType(Pc,PCJACOBI);
>   KSPSetFromOptions(ksp);
>   KSPSetTolerances(ksp,1.e-20,1.e-20,PETSC_DEFAULT,1000);
>   KSPSolve(ksp,b,x);
>
>
>   VecView(x,PETSC_VIEWER_STDOUT_WORLD);
>
>
>   PetscFinalize();
>   return 0;
> }
>
>
>
>
>


-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
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