[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
丁老师
ztdepyahoo at 163.com
Fri Aug 16 07:32:49 CDT 2013
thank you very much! could you please suggest me a robust preconditioner which is independent of the number of processor.
在 2013-08-16 19:54:01，"Matthew Knepley" <knepley at gmail.com> 写道：
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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