[wht]

Dear Colleagues,

I receive the following error after 'Remove unreachable sections of mesh' and 'Finalising parallel run' stages:

<...>
[780] Warning in regionSplit: received unassigned on procBoundary780to779 at patchFace 0
. Check synchronisation in caller
[780] Warning in regionSplit: received unassigned on procBoundary780to779 at patchFace 1. Check synchronisation in caller
[780] Warning in regionSplit: received unassigned on procBoundary780to779 at patchFace 2. Check synchronisation in caller
<...>

However, this error does not terminate meshing. I run checkMesh afterwards, and it claims that the mesh is OK. Should I get worried because of this error? I haven't started actual simulation yet.

Some information on my case: HPC computing, 500 million cells, OpenFOAM v2312, 1024 processors.

What I have found out so far is that this error is related to number of subdomains during decomposition and the size of the background mesh.

For example, for the following setup I have no issues:

numberOfSubdomains  512;

method          hierarchical;

coeffs
{
    n           (8 8 8);
}

(decomposedParDict)

scale   1;

xmin -0.1;
xmax 100.2;
ymin -0.05;
ymax 30.65;
zmin -0.2;
zmax 2.7;

// Size of the cells
deltax 0.099;
deltay 0.099;
deltaz 0.099;

lx #eval{ $xmax - $xmin};
ly #eval{ $ymax - $ymin};
lz #eval{ $zmax - $zmin};

xcells #eval { round($lx/$deltax)};
ycells #eval { round($ly/$deltay)};
zcells #eval { round($lz/$deltaz)};

vertices
(
//BLOCK 0
($xmin $ymin $zmin) //0
($xmax $ymin $zmin) //1
($xmax $ymax $zmin) //2
($xmin $ymax $zmin) //3
($xmin $ymin $zmax) //4
($xmax $ymin $zmax) //5
($xmax $ymax $zmax) //6
($xmin $ymax $zmax) //7
 );


blocks
(
    hex (0 1 2 3 4 5 6 7) ($xcells $ycells $zcells) simpleGrading (1 1 1)
);

edges
();

boundary
(
// <...>
);

(blockMeshDict)

The problems start when I increase the number of subdomains:

numberOfSubdomains  1024;

method          hierarchical;

coeffs
{
    n           (16 8 8);
}

(decomposedParDict)

I then get 'Cannot find matching point error':

<...>
Cannot find point in pts1 matching point 1665 coord13.6082 4.41765 19.75) in pts0 when using tolerance 2.8401e-05
<...>

However, this error can be fixed by changing size of the background mesh cell to:

// <...>
deltax 0.11;
deltay 0.11;
deltaz 0.11;
// <...>

(blockMeshDict)

After I fix this error, I get the 'Warning in regionSplit' as I said at the beginning.

log.snappyHexMesh https://sf.gsi.de/f/61ca36a457c8471eae8c/?dl=1 (45.1 Mb)

Best regards,
Ilya

---
GSI Helmholtzzentrum für Schwerionenforschung GmbH
Planckstr. 1, 64291 Darmstadt, Germany