[petsc-users] KSP linear solver

[Que Cat]

Dear Petsc-Users,

I debug my code. I solve the small linear system using KSP.
The matrix is:

row 0: (0, -123354)  (1, 6.92922e-310)  (2, 123354)  (3, 1.38582e-309)
row 1: (0, 1.3858e-309)  (1, 91156.6)  (2, 6.92901e-310)  (3, 91156.6)
row 2: (0, 8768.96)  (1, 2.47033e-323)  (2, -171955)  (3, 1.02212e-316)
 (4, 163186)  (5, 0)
row 3: (0, 0)  (1, -59201.7)  (2, 0)  (3, 156037)  (4, 0)  (5, 93996.1)
row 4: (2, 13422.8)  (3, 0)  (4, -13422.8)  (5, 0)
row 5: (2, 0)  (3, -58000.3)  (4, 0)  (5, 59201.7)

the RHS vector:

-9115.66
-17760.5
-425.926
-35400.9
9541.58
-17520.2

the solution I got was:

-2.00943e+52
-1.17929e+18
-2.00943e+52
7.121e+16
-2.00943e+52
-7.0943e+16

I checked with matlab and I got the totally different solution. I guess
there is something wrong with the linear solver I set up as follow:

    KSPSetOperators(ksp, mat_A, mat_A, SAME_NONZERO_PATTERN);

    // set the linear solve options
    KSPSetType(ksp, KSPGMRES);
    KSPGMRESSetRestart(ksp, 100);
    // set preconditioning options
    KSPGetPC(ksp, &pc);
    PCSetType(pc, PCBJACOBI);
    KSPSetFromOptions(ksp);
    // Solve the linear system
    KSPSolve(ksp,vec_rhs,vec_sol);

Could anyone give me a suggestion where should be the source of error?
Thank you!

Que
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