[petsc-users] DMGlobalToLocal acting weird

Manuel Valera mvalera-w at sdsu.edu
Mon Jul 2 14:58:24 CDT 2018

Hi guys,

I've noticed a bug in my code that seems to happen right after a call to
DMGlobalToLocalBegin/End and i can't seem to find a reason, it goes like

I create the DMDA (daScalars) with the following:

>  dof = 1
>  stw = 3
>                   dof,stw,PETSC_NULL_INTEGER,
> call DMSetFromOptions(daScalars,ierr)
> call DMSetUp(daScalars,ierr)

Then i read from a file the temperature and salinity fields of my problems,
those two are giving the trouble, i do it with this template:

call DMCreateGlobalVector(daScalars,gTemperature,ierr)
> call DMDAVecGetArrayF90(daScalars,gTemperature,arrtemp,ierr)
>    arrtemp = 99.0d0      !no idea why this fixes the problem -mv 62518
> call getCenterInfo(daScalars,  xstart, ystart, zstart, xend, yend, zend)
>             do k=zstart,zend-1
>                 do j=ystart,yend-1
>                     do i=xstart,xend-1
>                         arrtemp(i,j,k) = T0(i+1,j+1,k+1)
>                     enddo
>                 enddo
>             enddo
> call DMDAVecRestoreArrayF90(daScalars,gTemperature,arrtemp,ierr)
> call DMCreateLocalVector(daScalars,LocTemperature,ierr)
> call DMGlobalToLocalBegin(daScalars,gTemperature,INSERT_
> VALUES,LocTemperature,ierr)
> call DMGlobalToLocalEnd(daScalars,gTemperature,INSERT_VALUES,
> LocTemperature,ierr)

Now here is the first weirdness, if i assign a number to my array it does
behave as it should for the global quantity, but it must be a greater
number than the maximum of the field for this to happen, so i assign 99.0
arbitrarily, otherwise it doesn't read the array correctly, but it does as
of now,

Next, the last two lines communicate the array to the local counterparts,
but when i read LocTemperature with:

    call DMDAVecGetArrayReadF90(daScalars,DimTemperature,tdim,ierr)
>     print*,'Copied MinT0: ', minval(tdim)
>     call DMDAVecRestoreArrayReadF90(daScalars,DimTemperature,tdim,ierr)

That array minimum doesn't coincide with the global minimum, it should be
1.000 but it is just 0.000, the same happens with the Salinity following an
identical approach,

Any ideas on where to start looking? i have last month's PETSc build,

I'm running in 1 processor for now,


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