Issue resolved, stopped using the vector in the struct and used the one in the
arguments. Same issue was taking place in the Jacobian function which resulted
in error (-8) SNES_DIVERGED_LOCAL_MIN. Adjusting the jacobian function resolved
that issue as well.
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Today's Topics:
1. SNES solve residual vector - Fortran
(Khaled Nabil Shar Abdelaziz)
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Message: 1
Date: Sun, 7 Jan 2024 20:51:33 +0000
From: Khaled Nabil Shar Abdelaziz <kabde...@purdue.edu>
To: "petsc-users@mcs.anl.gov" <petsc-users@mcs.anl.gov>
Subject: [petsc-users] SNES solve residual vector - Fortran
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Hello everyone,
I am running into an issue with SNES solver where the residual in the first
iteration gets calculated fine, but on the 2nd iteration, even though it is
getting calculated locally, it doesn't seem to be "assigned" to the residual
vector correctly.
The residual vector here is referred to as petsc_PVector which is defined in a
type (struct). It seems like the first iteration, it behaves as expected and
that petsc_PVector gets updated, 2nd iteration however seems like there are 2
versions of it; one that is being passed into FormFunctionU, and another that
exists in the type (struct). This result in the residual on the 2nd iteration
to be exactly = 0 and convergence.
Any insights, suggestions, or experiences you can share regarding this issue
would be immensely appreciated. I'm particularly interested in understanding
why the residual vector behaves differently in the second iteration.
Best,
Khaled
The following is a snapshot of how I initialize and use SNES:
subroutine set_function_jacobian_to_solver_u(nlU)
type(variable_node_u),target,intent(inout)::nlU
PetscErrorCode::ierr
type(variable_node_part),pointer::var_nd_part
integer::ipart
! external FormFunctionU,FormJacobianU
do ipart=1,nlU%variable_node%npart
var_nd_part=>nlU%variable_node%parts(ipart)
PetscCallA(SNESSetFunction(var_nd_part%petsc_snes,var_nd_part%petsc_PVector,FormFunctionU,nlU,ierr))
PetscCallA(SNESSetJacobian(var_nd_part%petsc_snes,var_nd_part%petsc_KMatrix,var_nd_part%petsc_KMatrix,FormJacobianU,nlU,ierr))
PetscCallA(SNESSetFromOptions(var_nd_part%petsc_snes,ierr))
end do
var_nd_part=>null()
end subroutine set_function_jacobian_to_solver_u
subroutine FormFunctionU(petsc_snes,petsc_vector,petsc_PVector,nlU,ierr)
type(tSNES)::petsc_snes
type(tVec)::petsc_vector
type(tVec)::petsc_PVector
type(PetscScalar),pointer::vec_ptr_a(:),vec_ptr_b(:)
PetscErrorCode::ierr
type(variable_node_u),target::nlU
type(PetscScalar),pointer::val_petsc_PVector(:)
type(parameter),pointer::para_data
type(mesh),pointer::mesh_data
type(element),pointer::eles(:)
integer::k,i,flag,pid
PetscInt::its
para_data=>nlU%para_data
mesh_data=>nlU%mesh_data
eles=>nlU%eles
call MPI_Comm_rank(MPI_COMM_WORLD, pid, ierr)
call update_data_by_petsc_vector(nlU%variable_node,petsc_vector)
call set_petsc_PVector_to_zero(nlU%variable_node)
call update_petsc_PVector(nlU%variable_node)
flag = 0
do k=1,mesh_data%nel
call get_element_value(nlU%data_e, eles(k)%nnd_e,
mesh_data%elements(:,k), nlU%nvar_total, nlU%data)
call cal_element_ResidualU(nlU%PVector_e, eles(k), nlU%data_e,
para_data)
call set_petsc_PVector_values_by_element(nlU%variable_node,
nlU%PVector_e, eles(k)%nnd_e, mesh_data%elements(:,k))
end do
call update_petsc_PVector(nlU%variable_node)
para_data=>null()
mesh_data=>null()
eles=>null()
return
end subroutine FormFunctionU
call SNESSolve(nlU%variable_node%petsc_snes,PETSC_NULL_VEC,
nlU%variable_node%petsc_vector,error_petsc)
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