[petsc-users] Monotonic convergence in FGMRES.
Vijay S. Mahadevan
vijay.m at gmail.com
Tue Dec 21 12:53:52 CST 2010
Hi all,
I am running a linear problem discretized with FEM on a diffusion
reaction system, with discontinuous source distribution. When I run
FGMRes with geometric multigrid as its preconditioner, I notice that
every time after the restart in fgmres, the new residual is orders of
magnitude higher than the previous iteration. I might be wrong on this
but should the restart not preserve monotonicity in convergence ? Or
am I thinking of a different variant of Gmres here. Here's the
residual norm as a function of iteration with number of restarts=50.
40 KSP Residual norm 2.489810374358e-06
41 KSP Residual norm 1.585813670005e-06
42 KSP Residual norm 1.059211836025e-06
43 KSP Residual norm 6.701461059247e-07
44 KSP Residual norm 4.127634824940e-07
45 KSP Residual norm 2.511364148934e-07
46 KSP Residual norm 1.307034672896e-07
47 KSP Residual norm 7.105770015635e-08
48 KSP Residual norm 4.098578230710e-08
49 KSP Residual norm 2.426160176080e-08
-------------------------------------------------------------------------
50 KSP Residual norm 1.864914790828e+02
51 KSP Residual norm 6.741080961009e+01
52 KSP Residual norm 5.191621875736e+01
53 KSP Residual norm 4.513782866249e+01
54 KSP Residual norm 3.320195603375e+01
55 KSP Residual norm 2.699941296855e+01
56 KSP Residual norm 1.707998091297e+01
57 KSP Residual norm 1.219599670348e+01
Any suggestions to obtain a more smoother convergence would be much
appreciated. Thank you,
Vijay
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