[petsc-users] Question on local vec to global vec for dof > 1
Barry Smith
bsmith at mcs.anl.gov
Thu May 22 18:03:01 CDT 2014
Always do things one small step at at time. On one process what is x_vec_loc (use VecView again on it). Is it what you expect? Then run on two processes but call VecView on
x_vec_loc only on the first process. Is it what you expect?
Also what is vecpointer1d declared to be?
Barry
On May 22, 2014, at 4:44 PM, Danyang Su <danyang.su at gmail.com> wrote:
> On 22/05/2014 12:01 PM, Matthew Knepley wrote:
>> On Thu, May 22, 2014 at 1:58 PM, Danyang Su <danyang.su at gmail.com> wrote:
>> Hi All,
>>
>> I have a 1D transient flow problem (1 dof) coupled with energy balance (1 dof), so the total dof per node is 2.
>>
>> The whole domain has 10 nodes in z direction.
>>
>> The program runs well with 1 processor but failed in 2 processors. The matrix is the same for 1 processor and 2 processor but the rhs are different.
>>
>> The following is used to set the rhs value.
>>
>> call VecGetArrayF90(x_vec_loc, vecpointer, ierr)
>> vecpointer = (calculate the rhs value here)
>> call VecRestoreArrayF90(x_vec_loc,vecpointer,ierr)
>> call DMLocalToGlobalBegin(da,x_vec_loc,INSERT_VALUES, x_vec_gbl,ierr)
>> call DMLocalToGlobalEnd(da,x_vec_loc,INSERT_VALUES, x_vec_gbl,ierr)
>>
>> Vecview Correct Vecview Wrong
>> dof local node Process [0] Process [0] Process [0]
>> 1 1 1.395982780116148E-021 1.39598e-021 1.39598e-021
>> 1 2 0.000000000000000E+000 0 0
>> 1 3 0.000000000000000E+000 0 0
>> 1 4 5.642372883946980E-037 5.64237e-037 5.64237e-037
>> 1 5 0.000000000000000E+000 0 0
>> 1 6 -1.395982780116148E-021 -7.52316e-037 -1.39598e-021 Line A
>> 2 1 0.000000000000000E+000 7.52316e-037 0
>> 2 2 0.000000000000000E+000 0 0
>> 2 3 0.000000000000000E+000 1.68459e-016 0
>> 2 4 4.814824860968090E-035 0.1296 4.81482e-035
>> 2 5 0.000000000000000E+000 Process [1] Line B
>> 2 6 -1.371273884908092E-019 0 7.52316e-037 Line C
>> 0 0
>> Process [1] 0 1.68459e-016
>> 1 1 1.395982780116148E-021 4.81482e-035 0.1296 Line D
>> 1 2 -7.523163845262640E-037 0 1.37127e-019 Line E
>> 1 3 7.523163845262640E-037 -7.22224e-035 -7.22224e-035
>> 1 4 0.000000000000000E+000 7.22224e-035 7.22224e-035
>> 1 5 1.684590875336239E-016 0 0
>> 1 6 0.129600000000000 128623 128623
>> 2 1 1.371273884908092E-019 0 0 Line F
>> 2 2 -7.222237291452134E-035
>> 2 3 7.222237291452134E-035
>> 2 4 0.000000000000000E+000
>> 2 5 128623.169844761
>> 2 6 0.000000000000000E+000
>>
>> The red line (Line A, C, D and F) is the ghost values for 2 subdomains, but when run with 2 processor, the program treates Line B, C, D, and E as ghost values.
>> How can I handle this kind of local vector to global vector assembly?
>>
>> Why are you not using DMDAVecGetArrayF90()? This is exactly what it is for.
> Thanks, Matthew.
>
> I tried the following codes but still cannot get the correct global rhs vector
>
> call DMDAVecGetArrayF90(da,x_vec_loc,vecpointer1d,ierr)
> do i = 1,nvz !nvz is local node amount, here is 6
> vecpointer1d(0,i-1) = x_array_loc(i) !assume x_array_loc is the local rhs (the third column in the above mentioned data)
> vecpointer1d(1,i-1) = x_array_loc(i+nvz)
> end do
> call DMDAVecRestoreArrayF90(da,x_vec_loc,vecpointer1d,ierr)
> call DMLocalToGlobalBegin(da,x_vec_loc,INSERT_VALUES, x_vec_gbl,ierr)
> call DMLocalToGlobalEnd(da,x_vec_loc,INSERT_VALUES, x_vec_gbl,ierr)
>
>
> Now the rhs for 1 processor is as follows. It is not what I want.
>
> 1.39598e-021
> 0
> -0
> -0
> -0
> -0
> 5.64237e-037
> 4.81482e-035
> -0
> -0
> -7.52316e-037
> -7.22224e-035
> 7.52316e-037
> 7.22224e-035
> -0
> -0
> 1.68459e-016
> 128623
> 0.1296
> 0
>>
>> Matt
>>
>>
>> In fact, the codes can work if the dof and local node is as follows.
>> dof local node
>> 1 1
>> 2 1
>> 1 2
>> 2 2
>> 1 3
>> 2 3
>>
>> Thanks and regards,
>>
>> Danyang
>>
>>
>>
>> --
>> What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.
>> -- Norbert Wiener
>
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