[petsc-users] LineSearch question
Blaise Bourdin
bourdin at lsu.edu
Tue Aug 14 17:53:49 CDT 2012
HI,
I am trying to understand if the following behavior is normal / expected:
I am solving a quasi-static evolution where at each time step, SNESSolve is called. My validation problem is a _static_ problem with 2 time steps (i.e. 2 successive calls to SNESSolve with the same operator, jacobian, and right hand side). Furthermore, the problem is linear, so that the Jacobian is constant. I even reset the solution vector to the same value at each time step.
In this setting, I am expecting that at each time step, each SNESSolve should converge in exactly one iteration no matter what linesearch / snes type I use. Indeed, when setting the linesearch to l2 or cp, this is what I get. However, for all other choices, the second call to SNESSolve fails to converge with a SNESConvergedReason of -5 or -6.
The relevant code is as follow:
Call VecSet(solTemp,0.0_Kr,ierr);CHKERRQ(ierr)
Call FormInitialGuess(snesTemp,solTemp,MEF90Ctx,ierr);CHKERRQ(ierr)
Call VecCopy(solTemp,tmpvec,ierr)
Call SNESSolve(snesTemp,PETSC_NULL_OBJECT,solTemp,ierr);CHKERRQ(ierr)
Call VecCopy(tmpvec,soltemp,ierr)
Call SNESSolve(snesTemp,PETSC_NULL_OBJECT,solTemp,ierr);CHKERRQ(ierr)
Is this expected? I tried to call SNESLineSearchReset before the second call to SNESSolve, but this does not seem to have any effect.
Blaise
Below is the sample output using cp as the linesearch type in which case I get the expected convergence:
Solving time step 1: t= 1.00000E+00
0 SNES Function norm 3.742138023215e+00
Line search terminated: lambda = 1, fnorms = 2.1936e-08
1 SNES Function norm 2.193598339906e-08
SNES Object:(temp_) 1 MPI processes
type: ls
maximum iterations=50, maximum function evaluations=10000
tolerances: relative=1e-08, absolute=1e-50, solution=1e-08
total number of linear solver iterations=15
total number of function evaluations=3
KSP Object: (temp_) 1 MPI processes
type: cg
maximum iterations=10000
tolerances: relative=1e-08, absolute=1e-50, divergence=10000
left preconditioning
using nonzero initial guess
using PRECONDITIONED norm type for convergence test
PC Object: (temp_) 1 MPI processes
type: icc
0 levels of fill
tolerance for zero pivot 2.22045e-14
using Manteuffel shift
matrix ordering: natural
factor fill ratio given 1, needed 1
Factored matrix follows:
Matrix Object: 1 MPI processes
type: seqsbaij
rows=104, cols=104
package used to perform factorization: petsc
total: nonzeros=381, allocated nonzeros=381
total number of mallocs used during MatSetValues calls =0
block size is 1
linear system matrix = precond matrix:
Matrix Object: 1 MPI processes
type: seqaij
rows=104, cols=104
total: nonzeros=658, allocated nonzeros=658
total number of mallocs used during MatSetValues calls =0
not using I-node routines
SNESLineSearch Object: (temp_) 1 MPI processes
type: cp
maxstep=1.000000e+08, minlambda=1.000000e-12
tolerances: relative=1.000000e-08, absolute=1.000000e-15, lambda=1.000000e-08
maximum iterations=1
SNESTemp converged in in 1 iterations. SNESConvergedReason is 3
0 SNES Function norm 3.742138023215e+00
Line search: lambdas = [1, 0], ftys = [2.42597, 4.85193]
Line search terminated: lambda = 2, fnorms = 2.1936e-08
1 SNES Function norm 2.193598717772e-08
SNES Object:(temp_) 1 MPI processes
type: ls
maximum iterations=50, maximum function evaluations=10000
tolerances: relative=1e-08, absolute=1e-50, solution=1e-08
total number of linear solver iterations=15
total number of function evaluations=3
KSP Object: (temp_) 1 MPI processes
type: cg
maximum iterations=10000
tolerances: relative=1e-08, absolute=1e-50, divergence=10000
left preconditioning
using nonzero initial guess
using PRECONDITIONED norm type for convergence test
PC Object: (temp_) 1 MPI processes
type: icc
0 levels of fill
tolerance for zero pivot 2.22045e-14
using Manteuffel shift
matrix ordering: natural
factor fill ratio given 1, needed 1
Factored matrix follows:
Matrix Object: 1 MPI processes
type: seqsbaij
rows=104, cols=104
package used to perform factorization: petsc
total: nonzeros=381, allocated nonzeros=381
total number of mallocs used during MatSetValues calls =0
block size is 1
linear system matrix = precond matrix:
Matrix Object: 1 MPI processes
type: seqaij
rows=104, cols=104
total: nonzeros=658, allocated nonzeros=658
total number of mallocs used during MatSetValues calls =0
not using I-node routines
SNESLineSearch Object: (temp_) 1 MPI processes
type: cp
maxstep=1.000000e+08, minlambda=1.000000e-12
tolerances: relative=1.000000e-08, absolute=1.000000e-15, lambda=1.000000e-08
maximum iterations=1
SNESTemp converged in in 1 iterations. SNESConvergedReason is 3
when using the default linesearch (bt), the second SNESSolve fails:
Solving time step 1: t= 1.00000E+00
0 SNES Function norm 3.742138023215e+00
Line search: Using full step: fnorm 3.742138023215e+00 gnorm 2.193598339906e-08
1 SNES Function norm 2.193598339906e-08
SNES Object:(temp_) 1 MPI processes
type: ls
maximum iterations=50, maximum function evaluations=10000
tolerances: relative=1e-08, absolute=1e-50, solution=1e-08
total number of linear solver iterations=15
total number of function evaluations=2
KSP Object: (temp_) 1 MPI processes
type: cg
maximum iterations=10000
tolerances: relative=1e-08, absolute=1e-50, divergence=10000
left preconditioning
using nonzero initial guess
using PRECONDITIONED norm type for convergence test
PC Object: (temp_) 1 MPI processes
type: icc
0 levels of fill
tolerance for zero pivot 2.22045e-14
using Manteuffel shift
matrix ordering: natural
factor fill ratio given 1, needed 1
Factored matrix follows:
Matrix Object: 1 MPI processes
type: seqsbaij
rows=104, cols=104
package used to perform factorization: petsc
total: nonzeros=381, allocated nonzeros=381
total number of mallocs used during MatSetValues calls =0
block size is 1
linear system matrix = precond matrix:
Matrix Object: 1 MPI processes
type: seqaij
rows=104, cols=104
total: nonzeros=658, allocated nonzeros=658
total number of mallocs used during MatSetValues calls =0
not using I-node routines
SNESLineSearch Object: (temp_) 1 MPI processes
type: bt
interpolation: cubic
alpha=1.000000e-04
maxstep=1.000000e+08, minlambda=1.000000e-12
tolerances: relative=1.000000e-08, absolute=1.000000e-15, lambda=1.000000e-08
maximum iterations=40
SNESTemp converged in in 1 iterations. SNESConvergedReason is 3
0 SNES Function norm 3.742138023215e+00
Line search: Using full step: fnorm 3.742138023215e+00 gnorm 1.871069011453e+00
1 SNES Function norm 1.871069011453e+00
Line search: Using full step: fnorm 1.871069011453e+00 gnorm 1.247379340865e+00
2 SNES Function norm 1.247379340865e+00
Line search: Using full step: fnorm 1.247379340865e+00 gnorm 9.355345056231e-01
3 SNES Function norm 9.355345056231e-01
Line search: Using full step: fnorm 9.355345056231e-01 gnorm 7.484276044882e-01
4 SNES Function norm 7.484276044882e-01
Line search: Using full step: fnorm 7.484276044882e-01 gnorm 6.236896704016e-01
5 SNES Function norm 6.236896704016e-01
Line search: Using full step: fnorm 6.236896704016e-01 gnorm 5.345911460556e-01
6 SNES Function norm 5.345911460556e-01
Line search: Using full step: fnorm 5.345911460556e-01 gnorm 4.677672528597e-01
7 SNES Function norm 4.677672528597e-01
Line search: Using full step: fnorm 4.677672528597e-01 gnorm 4.157931136937e-01
8 SNES Function norm 4.157931136937e-01
Line search: Using full step: fnorm 4.157931136937e-01 gnorm 3.742138023528e-01
9 SNES Function norm 3.742138023528e-01
Line search: Using full step: fnorm 3.742138023528e-01 gnorm 3.401943657960e-01
10 SNES Function norm 3.401943657960e-01
Line search: Using full step: fnorm 3.401943657960e-01 gnorm 3.118448353285e-01
11 SNES Function norm 3.118448353285e-01
Line search: Using full step: fnorm 3.118448353285e-01 gnorm 2.878567710844e-01
12 SNES Function norm 2.878567710844e-01
Line search: Using full step: fnorm 2.878567710844e-01 gnorm 2.672955731592e-01
13 SNES Function norm 2.672955731592e-01
Line search: Using full step: fnorm 2.672955731592e-01 gnorm 2.494758682895e-01
14 SNES Function norm 2.494758682895e-01
Line search: Using full step: fnorm 2.494758682895e-01 gnorm 2.338836265275e-01
15 SNES Function norm 2.338836265275e-01
Line search: Using full step: fnorm 2.338836265275e-01 gnorm 2.201257661485e-01
16 SNES Function norm 2.201257661485e-01
Line search: Using full step: fnorm 2.201257661485e-01 gnorm 2.078965569222e-01
17 SNES Function norm 2.078965569222e-01
Line search: Using full step: fnorm 2.078965569222e-01 gnorm 1.969546328772e-01
18 SNES Function norm 1.969546328772e-01
Line search: Using full step: fnorm 1.969546328772e-01 gnorm 1.871069012364e-01
19 SNES Function norm 1.871069012364e-01
Line search: Using full step: fnorm 1.871069012364e-01 gnorm 1.781970487991e-01
20 SNES Function norm 1.781970487991e-01
Line search: Using full step: fnorm 1.781970487991e-01 gnorm 1.700971829468e-01
21 SNES Function norm 1.700971829468e-01
Line search: Using full step: fnorm 1.700971829468e-01 gnorm 1.627016532554e-01
22 SNES Function norm 1.627016532554e-01
Line search: Using full step: fnorm 1.627016532554e-01 gnorm 1.559224177048e-01
23 SNES Function norm 1.559224177048e-01
Line search: Using full step: fnorm 1.559224177048e-01 gnorm 1.496855209981e-01
24 SNES Function norm 1.496855209981e-01
Line search: Using full step: fnorm 1.496855209981e-01 gnorm 1.439283855764e-01
25 SNES Function norm 1.439283855764e-01
Line search: Using full step: fnorm 1.439283855764e-01 gnorm 1.385977046303e-01
26 SNES Function norm 1.385977046303e-01
Line search: Using full step: fnorm 1.385977046303e-01 gnorm 1.336477866088e-01
27 SNES Function norm 1.336477866088e-01
Line search: Using full step: fnorm 1.336477866088e-01 gnorm 1.290392422439e-01
28 SNES Function norm 1.290392422439e-01
Line search: Using full step: fnorm 1.290392422439e-01 gnorm 1.247379341700e-01
29 SNES Function norm 1.247379341700e-01
Line search: Using full step: fnorm 1.247379341700e-01 gnorm 1.207141298427e-01
30 SNES Function norm 1.207141298427e-01
Line search: Using full step: fnorm 1.207141298427e-01 gnorm 1.169418132858e-01
31 SNES Function norm 1.169418132858e-01
Line search: Using full step: fnorm 1.169418132858e-01 gnorm 1.133981219747e-01
32 SNES Function norm 1.133981219747e-01
Line search: Using full step: fnorm 1.133981219747e-01 gnorm 1.100628830937e-01
33 SNES Function norm 1.100628830937e-01
Line search: Using full step: fnorm 1.100628830937e-01 gnorm 1.069182292915e-01
34 SNES Function norm 1.069182292915e-01
Line search: Using full step: fnorm 1.069182292915e-01 gnorm 1.039482784783e-01
35 SNES Function norm 1.039482784783e-01
Line search: Using full step: fnorm 1.039482784783e-01 gnorm 1.011388655469e-01
36 SNES Function norm 1.011388655469e-01
Line search: Using full step: fnorm 1.011388655469e-01 gnorm 9.847731645400e-02
37 SNES Function norm 9.847731645400e-02
Line search: Using full step: fnorm 9.847731645400e-02 gnorm 9.595225705796e-02
38 SNES Function norm 9.595225705796e-02
Line search: Using full step: fnorm 9.595225705796e-02 gnorm 9.355345063171e-02
39 SNES Function norm 9.355345063171e-02
Line search: Using full step: fnorm 9.355345063171e-02 gnorm 9.127165915308e-02
40 SNES Function norm 9.127165915308e-02
Line search: Using full step: fnorm 9.127165915308e-02 gnorm 8.909852441151e-02
41 SNES Function norm 8.909852441151e-02
Line search: Using full step: fnorm 8.909852441151e-02 gnorm 8.702646570443e-02
42 SNES Function norm 8.702646570443e-02
Line search: Using full step: fnorm 8.702646570443e-02 gnorm 8.504859148402e-02
43 SNES Function norm 8.504859148402e-02
Line search: Using full step: fnorm 8.504859148402e-02 gnorm 8.315862278451e-02
44 SNES Function norm 8.315862278451e-02
Line search: Using full step: fnorm 8.315862278451e-02 gnorm 8.135082663716e-02
45 SNES Function norm 8.135082663716e-02
Line search: Using full step: fnorm 8.135082663716e-02 gnorm 7.961995798542e-02
46 SNES Function norm 7.961995798542e-02
Line search: Using full step: fnorm 7.961995798542e-02 gnorm 7.796120886084e-02
47 SNES Function norm 7.796120886084e-02
Line search: Using full step: fnorm 7.796120886084e-02 gnorm 7.637016378216e-02
48 SNES Function norm 7.637016378216e-02
Line search: Using full step: fnorm 7.637016378216e-02 gnorm 7.484276050661e-02
49 SNES Function norm 7.484276050661e-02
Line search: Using full step: fnorm 7.484276050661e-02 gnorm 7.337525539874e-02
50 SNES Function norm 7.337525539874e-02
SNES Object:(temp_) 1 MPI processes
type: ls
maximum iterations=50, maximum function evaluations=10000
tolerances: relative=1e-08, absolute=1e-50, solution=1e-08
total number of linear solver iterations=693
total number of function evaluations=51
KSP Object: (temp_) 1 MPI processes
type: cg
maximum iterations=10000
tolerances: relative=1e-08, absolute=1e-50, divergence=10000
left preconditioning
using nonzero initial guess
using PRECONDITIONED norm type for convergence test
PC Object: (temp_) 1 MPI processes
type: icc
0 levels of fill
tolerance for zero pivot 2.22045e-14
using Manteuffel shift
matrix ordering: natural
factor fill ratio given 1, needed 1
Factored matrix follows:
Matrix Object: 1 MPI processes
type: seqsbaij
rows=104, cols=104
package used to perform factorization: petsc
total: nonzeros=381, allocated nonzeros=381
total number of mallocs used during MatSetValues calls =0
block size is 1
linear system matrix = precond matrix:
Matrix Object: 1 MPI processes
type: seqaij
rows=104, cols=104
total: nonzeros=658, allocated nonzeros=658
total number of mallocs used during MatSetValues calls =0
not using I-node routines
SNESLineSearch Object: (temp_) 1 MPI processes
type: bt
interpolation: cubic
alpha=1.000000e-04
maxstep=1.000000e+08, minlambda=1.000000e-12
tolerances: relative=1.000000e-08, absolute=1.000000e-15, lambda=1.000000e-08
maximum iterations=40
SNESTemp converged in in 50 iterations. SNESConvergedReason is -5
--
Department of Mathematics and Center for Computation & Technology
Louisiana State University, Baton Rouge, LA 70803, USA
Tel. +1 (225) 578 1612, Fax +1 (225) 578 4276 http://www.math.lsu.edu/~bourdin
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