Dear Chapel developers,
This is Akihiro Hayashi, postdoc at Rice University.
I'm writing this to ask array copy failure in chapel.
I'm trying to evaluate some chapel benchmark across multiple nodes but I get
strange error.
Please note that I'm using old version of chapel compiler (r21945) with
qthread-1.10 and GASNet-1.20.2(infiniband-conduit, mpi-spawner) because the
latest version does not work.
With the latest version of chapel compiler (r22568) with qthread-1.10 and
GASNet-1.22.0(infiniband-conduit, mpi-spawner), I get SEGV when running simple
program (coforall loc in Locales do on loc { writeln(loc); }) across multiple
nodes with mpi spawner.
This is another problem but I have not investigated this problem yet. I'll work
on this later.
The following problem might be fixed in the latest version, but any comments
and suggestions are appreciated.
Here is part of my code.
The main data structure is a 3-dimensional array, which is declared as a
distributed array that each of its element refers to a 2-dimension array.
You can see array copy statement (liBlock = lkji_tiles(k,k,k+1).tile_array;) in
Line 11. I want to use this copy statement because the Chapel compiler
generates bulk transfer code, which accelerates program execution.
// Code
1: const zero: int(32) = 0;
2: var tile_array_indices = {zero..tileSize-1,zero..tileSize-1};
3: class Tile {
4: var tile_array: [tile_array_indices] real;
5: }
6: var proto_ijk_space = {zero..numTiles_2-1, zero..numTiles_2,
zero..numTiles_2};
7: var ijk_space = proto_ijk_space dmapped Block(boundingBox=proto_ijk_space);
8: var lkji_tiles: [ijk_space] Tile;
...
9 :begin {
...
10: var liBlock: [tile_array_indices] real;
11: liBlock = lkji_tiles(k,k,k+1).tile_array;
12: for (m,n) in tile_array_indices {
13: if (liBlock(m,n) != lkji_tiles(k,k,k+1).tile_array(m,n)) {
14: invalid = true;
15: }
16: }
17: if (invalid) { writln("Copy Failed");}
18: ...
19: }
...
In my experiment, when running the program on 2 or more locales, the program
prints "Copy Failed" which means "liBlock = lkji_tiles(k,k,k+1).tile_array;"
in Line 11 failed.
This happens sometime (not always). and I confirmed the copy is successfully
done if I replace the array copy in Line 11 with copy loop.
Additionally, I also see the same behavior when I replace the array copy in
Line 11 with liBlock._value.doiBulkTransfer(lkji_tiles(k,k,k+1).tile_array);.
Here is an output log at runtime when I compile the program with -s
debugBulkTransfer (tileSize=200):
-- Log starts here
In DefaultRectangularArr.doiBulkTransfer(): Alo=(0, 0), Blo=(0, 0), len=40000,
elemSize=8;
-- End of Log
In both cases, the runtime internally calls chpl_comm_get API(*) and the API
takes the above parameters.
I think it looks good.
(*) Please take a look at doiBulkTransfer function in
CHPL_HOME/modules/internal/DefaultRectangular.chpl
Any comments and suggestions are appreciated.
Best regards,
Akihiro
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