[dune-pdelab] Scalability issue in overlapping solvers

[Aswin vs]

Hello,

Can somebody suggest me how to get good scalability while using the
overlapping solvers in DUNE. I tried the following test example in DUNE
PDELab, but not getting good scalability.
Thank you.

$  mpirun -np 1 ./test-heat-instationary-periodic
.
.
.
STAGE 2 time (to):   1.5000e-02.
=== matrix setup skipped (matrix already allocated)
=== matrix assembly (max) 0.9944 s
=== residual assembly (max) 0.4861 s
=== solving (reduction: 1e-10) === Dune::BiCGSTABSolver
=== rate=0.8397, T=12.57, TIT=0.09524, IT=132
12.68 s
::: timesteps           2 (2)
::: nl iterations     565 (565)
::: lin iterations    565 (565)
::: assemble time    8.0477e+00 (8.0477e+00)
::: lin solve time   5.3414e+01 (5.3414e+01)
---------------------------------------------------------------------------------------
$ mpirun -np 2 ./testheat-instationary-periodic
.
.
.
STAGE 2 time (to):   1.5000e-02.
=== matrix setup skipped (matrix already allocated)
=== matrix assembly (max) 0.5053 s
=== residual assembly (max) 0.2465 s
=== solving (reduction: 1e-10) === Dune::BiCGSTABSolver
=== rate=0.9268, T=26.95, TIT=0.08895, IT=303
27.05 s
::: timesteps           2 (2)
::: nl iterations    1254 (1254)
::: lin iterations   1254 (1254)
::: assemble time    4.0910e+00 (4.0910e+00)
::: lin solve time   1.1201e+02 (1.1201e+02)
---------------------------------------------------------------------------------------
$ mpirun -np 4 ./testheat-instationary-periodic
.
.
.
STAGE 2 time (to):   1.5000e-02.
=== matrix setup skipped (matrix already allocated)
=== matrix assembly (max) 0.271 s
=== residual assembly (max) 0.1318 s
=== solving (reduction: 1e-10) === Dune::BiCGSTABSolver
=== rate=0.9232, T=26.02, TIT=0.0894, IT=291
26.11 s
::: timesteps           2 (2)
::: nl iterations    1249 (1249)
::: lin iterations   1249 (1249)
::: assemble time    2.1746e+00 (2.1746e+00)
::: lin solve time   1.1165e+02 (1.1165e+02)
---------------------------------------------------------------------------------------
$ mpirun -np 8 ./testheat-instationary-periodic
.
.
.
STAGE 2 time (to):   1.5000e-02.
=== matrix setup skipped (matrix already allocated)
=== matrix assembly (max) 0.1772 s
=== residual assembly (max) 0.08259 s
=== solving (reduction: 1e-10) === Dune::BiCGSTABSolver
=== rate=0.9288, T=30.81, TIT=0.09751, IT=316
30.89 s
::: timesteps           2 (2)
::: nl iterations    1329 (1329)
::: lin iterations   1329 (1329)
::: assemble time    1.3485e+00 (1.3485e+00)
::: lin solve time   1.2796e+02 (1.2796e+02)


-- 
Aswin V.S.
Research Associate-I
School of Mathematics
*Indian Institute of Science Education and Research Thiruvananthapuram*
Contact: +91 8089542946 / 7994312946
*_____________________________________*
"The secret of life is not enjoyment but education through experience."
― Swami Vivekananda
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