# [Trilinos-Users] AztecOO: result is zero?

dorian.krause at usi.ch dorian.krause at usi.ch
Mon Apr 4 04:27:36 MDT 2011

```Hi,

without knowing much details about AztecOO,
it seems to me that this is correct: The example
starts from a random initial guess and converges
to zero (that's a often used test for iterative solvers).

On Apr 4, 2011, at 12:13 PM, Sensei wrote:

Dear all,

I have successfully used the FECsrMatrix class with a graph, and I am happy about it. Now I've moved to another library from the tutoral: AztecOO.

However, I am missing something: I always have a zero vector as result of a linear problem. Fearing a mistake of mine, I've compiled Didasko/AztecOO ex2.cpp, since its matrix was exactly what I've been programming for, but alas, I get the same zero vector.

What am I missing? I'm pasting the debugger's output.

Thanks!

GNU gdb 6.3.50-20050815 (Apple version gdb-1518) (Sat Feb 12 02:52:12 UTC 2011)
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This GDB was configured as "x86_64-apple-darwin".tty /dev/ttys001

[Switching to process 1489 thread 0x0]

Epetra::CrsMatrix
Number of Global Rows        = 5
Number of Global Cols        = 5
Number of Global Diagonals   = 5
Number of Global Nonzeros    = 13
Global Maximum Num Entries   = 3

Number of My Rows        = 3
Number of My Cols        = 4
Number of My Diagonals   = 3
Number of My Nonzeros    = 8
My Maximum Num Entries   = 3

Epetra::CrsMatrix
Number of My Rows        = 2
Number of My Cols        = 3
Number of My Diagonals   = 2
Number of My Nonzeros    = 5
My Maximum Num Entries   = 3

Processor    Row Index    Col Index           Value
0             0             0                       2
0             0             1                      -1
0             1             0                      -1
0             1             1                       2
0             1             2                      -1
0             2             1                      -1
0             2             2                       2
0             2             3                      -1
1             3             3                       2
1             3             4                      -1
1             3             2                      -1
1             4             3                      -1
1             4             4                       2

Epetra::Vector
Epetra::Vector
MyPID           GID               Value
0             0               -0.562082
0             1               -0.905911
0             2               0.0655345
1             3              -0.0359305
1             4               0.0655658

*******************************************************
***** Problem: Epetra::CrsMatrix
***** Preconditioned GMRESR solution
***** AztecOO Operator
***** No scaling
*******************************************************

iter:    0           residual = 1.000000e+00
iter:    1           residual = 2.046639e-16

Solution time: 0.001977 (sec.)
total iterations: 1

Epetra::Vector
Epetra::Vector
MyPID           GID               Value
0             0                       0
0             1                       0
0             2                       0
1             3                       0
1             4                       0

Program ended with exit code: 0
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```