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Support Open MPI 4.1 and 5.0 - #529
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Review comments at @mpi-proxy-split/mpi-wrappers/Makefile:
- Line 112: Update the mpi_stub_objects.c rule so changes to MPICC invalidate
the generated source and rerun its preprocessing recipe, preventing stale MPI
predefined objects from being linked.
Review comments at @mpi-proxy-split/mpi-wrappers/mpi_comm_wrappers.cpp:
- Around line 411-412: Update is_predefined_keyval to reserve MPI_APPNUM,
MPI_LASTUSEDCODE, and MPI_UNIVERSE_SIZE alongside the existing predefined
keyvals, preventing them from being allocated as user keyvals.
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📒 Files selected for processing: 25
.github/workflows/mana-tests.ymlREADME.mdmpi-proxy-split/Makefilempi-proxy-split/lower-half/lower-half-api.hmpi-proxy-split/lower-half/lower-half.cppmpi-proxy-split/mpi-wrappers/Makefilempi-proxy-split/mpi-wrappers/fortran_handles.hmpi-proxy-split/mpi-wrappers/generate-mpi-fortran-wrappers.pympi-proxy-split/mpi-wrappers/generate-mpi-stub-objects.pympi-proxy-split/mpi-wrappers/mpi_comm_wrappers.cppmpi-proxy-split/mpi-wrappers/mpi_file_wrappers.cppmpi-proxy-split/mpi-wrappers/mpi_fortran_wrappers.txtmpi-proxy-split/mpi-wrappers/mpi_group_wrappers.cppmpi-proxy-split/mpi-wrappers/mpi_op_wrappers.cppmpi-proxy-split/mpi-wrappers/mpi_request_wrappers.cppmpi-proxy-split/mpi-wrappers/mpi_stub_data.cmpi-proxy-split/mpi_plugin.cppmpi-proxy-split/p2p_drain_send_recv.cppmpi-proxy-split/seq_num.cppmpi-proxy-split/test/Makefilempi-proxy-split/test/autotest.pympi-proxy-split/test/dlopen_mpi.cmpi-proxy-split/test/fortran_handles.f90mpi-proxy-split/virtual_id.cppmpi-proxy-split/virtual_id.h
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LGTM.
There are some commits that are repeated from earlier PRs. Normally, when we rebase this PR, the duplicate commits will disappear. But if there was a minor change in the commit either in this PR or the earlier PR, then after rebasing, we can do git log, and we'll see duplicate commit messages in the history. This will show that we made a mistake in rebasing, and then choose only the "canonical" commit for rebasing.
get_real_id_slow() looks a predefined constant up in the table of constants. It guessed the key from the handle: if the low 32 bits, read as an int, were less than the whole 64-bit value, it used the low 32 bits. That suits MPICH, whose 32-bit handles the table holds sign-extended (MPI_LONG_INT is negative). But with 64-bit handles (Open MPI), a constant is an address, and one with bit 31 set, such as 0x82c8af80, missed: MANA spun in get_virt_id_entry() with "Invalid MPI handle value". The key now depends on the size of the handle type, and is_predefined_id() and get_virt_id_desc() use it too. Co-authored-by: Eudald Pizarro Cami <eudald.pizarro@bsc.es>
With MPICH, a predefined constant has the same value in both halves: an integer that mpi.h defines. With Open MPI, it is the address of an object of the MPI library, so the upper half's value (libmpistub.so's object) differs from the lower half's. MANA used the upper half's value as a real handle in several places. It passed MPI_UNSIGNED_LONG (the Collective Clock's messages), MPI_BYTE (the P2P drain's receive) and MPI_COMM_WORLD (localRankToGlobalRank()) to the lower half: the first checkpoint failed with MPI_ERR_TYPE. It set the real request of a request that it completes to MPI_REQUEST_NULL (P2P drain, non-blocking collectives, complete_virt_request()), and compared real requests with it: after a checkpoint, the program's next MPI_Wait() tested a bogus request forever. new_virt_comm() compared the real communicator with MPI_COMM_NULL. And MPI_Errhandler and MPI_Info, which MANA does not virtualize, went to and from the lower half untranslated. These now use the lower half's values (lh_info->MANA_*), and lower_half_handle() and upper_half_handle() translate a predefined errhandler or info. The unused map of lower-to-upper constants is now filled by set_upper_to_lower(), instead of by a separate list. The blocking P2P drain also named MPI_COMM_WORLD and MPI_COMM_SELF by their handles, which it shares between ranks. With Open MPI, a handle is an address, which can differ between the programs of an MPMD job, so it names them 0 and 1 now.
With Open MPI, a predefined handle is the address of an object in
libmpi.so: MPI_COMM_WORLD is &ompi_mpi_comm_world. In the upper half,
libmpistub.so takes the place of libmpi.so, but it did not define these
objects, so libmana.so and Open MPI programs did not load ("undefined
symbol: ompi_mpi_real").
generate-mpi-stub-objects.py now writes their definitions. It takes
their names from mpi.h, which the MPI library's mpicc preprocesses, and
their sizes from the sizes to which Open MPI pads them, the same in Open
MPI 4.1 and 5.0: a program may have a copy relocation of an object.
With another MPI library, it defines nothing. mpi_stub_data.c defines
Open MPI's predefined attribute callbacks (MPI_COMM_DUP_FN, ...), which
are functions of the library.
libmana.so itself refers to these objects, so it now needs
libmpistub.so: a program that loads the MPI library with dlopen() has
not loaded libmpistub.so before libmana.so.
The Fortran wrappers passed a Fortran handle, an INTEGER, to the C function as the C handle. That works with MPICH, whose C handles are ints with the same values, except MPI_File, a pointer. With Open MPI, C handles are pointers and Fortran handles are indices into the MPI library's tables: a wrapper read 8 bytes from a 4-byte INTEGER, or wrote 8 bytes into it, and MPI_COMM_WORLD (0) was not a C handle. The wrappers that generate-mpi-fortran-wrappers.py writes now convert each handle with mana_f2c() and mana_c2f() (fortran_handles.h): the inputs before the call, the outputs after it, and arrays of handles through a copy. When a C handle is an int (MPICH), the conversion does nothing. Otherwise, the Fortran handle of a virtual handle is the virtual handle itself, which has 32 bits and stays valid across a restart. That of a predefined constant is the MPI library's, which init_predefined_virt_ids() records from MPI_Comm_c2f() and others in the lower half (lh_info->handle_c2f()). For that, each constant now has a kind, and the kinds move to lower-half-api.h. handle_c2f is the last field of LowerHalfInfo_t, so that no other field moves. This also fixes Fortran's MPI_FILE_OPEN() with MPICH, which wrote an 8-byte MPI_File into a 4-byte INTEGER. Co-authored-by: Eudald Pizarro Cami <eudald.pizarro@bsc.es>
fortran_handles creates handles from Fortran before its loop: a communicator with MPI_COMM_SPLIT (the ranks in reverse order), one with MPI_COMM_DUP and MPI_ERRORS_RETURN, a group, a vector datatype, and a struct datatype from an array of datatypes. Each iteration uses them across the checkpoints and restarts, waits with MPI_WAITALL and MPI_WAITANY, and creates and frees a communicator and a datatype, which must then be MPI_COMM_NULL and MPI_DATATYPE_NULL.
dlopen_mpi is not linked with the MPI library, and used MPI_COMM_WORLD, MPI_INT and MPI_SUM. With Open MPI, these are the addresses of objects in the library, so the program did not link, and the build of the tests stopped there. It now gets these objects from the library with dlsym().
In C++, Open MPI 4.1's mpi.h also declares the C++ bindings of MPI-2, whose code is in libmpi_cxx.so. libmana.so, which mpic++ builds, then needed symbols such as MPI::Datatype::Free(), which nothing in the upper half defines: no program loaded. The upper half is now built with OMPI_SKIP_MPICXX and MPICH_SKIP_MPICXX, which leave the bindings out.
The workflow now also runs the tests with Ubuntu's Open MPI (5.0.10 in Ubuntu 26.04). Open MPI refuses to run as root, as in the container, unless OMPI_ALLOW_RUN_AS_ROOT and OMPI_ALLOW_RUN_AS_ROOT_CONFIRM are set, and to start more ranks than there are cores, without --oversubscribe. The MPICH job is now "Ubuntu 26.04, MPICH". Tested in an ubuntu:26.04 container with the job's steps: 24 of 24 tests passed.
The README now says which MPI library ./configure uses, that switching libraries needs "make clean", how to build with Open MPI, and what Open MPI's mpirun needs in a container.
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Summary
Make MANA run with Open MPI 4.1 and 5.0, in C and in Fortran. Before this PR, no program loaded under MANA with Open MPI. Most problems come from one difference: with MPICH, a predefined handle is an integer constant, the same in both halves; with Open MPI, handles are pointers, and a predefined handle is the address of an object in the MPI library, which differs between the upper half (libmpistub.so) and the lower half. 9 commits:
get_real_id_slow()guessed the lookup key from the handle's two halves; with Open MPI, a constant with bit 31 set missed, and MANA spun on "Invalid MPI handle value". The key now depends on the size of the handle type.MPI_UNSIGNED_LONG,MPI_BYTEandMPI_COMM_WORLD(the first checkpoint failed withMPI_ERR_TYPE), real requests set to or compared withMPI_REQUEST_NULL(the program'sMPI_Waithung after a checkpoint), and untranslatedMPI_InfoandMPI_Errhandler. The blocking drain's dummy protocol now namesMPI_COMM_WORLDandMPI_COMM_SELF0 and 1, not by their handles, which can differ between the programs of an MPMD job.generate-mpi-stub-objects.pydefines the 107 predefined objects (names frommpi.h, sizes from Open MPI's padded sizes, the same in 4.1 and 5.0);mpi_stub_data.cdefines the 12 predefined attribute callbacks.libmana.sonow needslibmpistub.so, since it refers to these objects too.INTEGERas the C handle. The generated wrappers now convert each handle (scalars, outputs, and the arrays ofMPI_Waitall,MPI_Waitany,MPI_Testall,MPI_TestanyandMPI_Type_create_struct). With MPICH, the conversion does nothing, except forMPI_File, a pointer. Otherwise, the Fortran handle of a virtual handle is the virtual handle itself (32 bits, valid across a restart), and that of a predefined constant comes from the lower half'sMPI_*_c2f(), through a newlh_info->handle_c2f().fortran_handlescreates communicators, a group and derived datatypes from Fortran, and uses them across checkpoints and restarts.dlsym().mpi.hdeclares the MPI-2 C++ bindings in C++; the upper half is now built withOMPI_SKIP_MPICXXandMPICH_SKIP_MPICXX.mainrequires the old name).make cleanbefore switching MPI libraries.Notes for review
MPI_Filehandles are converted (before,MPI_FILE_OPENwrote 8 bytes into a 4-byteINTEGER); andlibmana.soloadslibmpistub.soas a dependency.handle_c2fis the last field ofLowerHalfInfo_t, so that no other field moves: the lower half's Makefile has no header dependencies, and an incremental build would keep stale objects.MPI_File_opencreates two virtual handles and saves the restart parameters under the one that it does not return;MPI_File_closedoes not free the virtual handle.libmpi_cxx.sois replaced like the other MPI libraries.MPI_*_NULL" is covered by Fix MPI_Comm_free and the Collective Clock's drain #545, which also nullsMPI_File_close's handle.Testing
autotest.py, 24 tests (with the newfortran_handles):Before this PR, with Open MPI 5.0.9, no test passed: no program loaded. Each commit builds on its own with MPICH.
After the rebase onto main (with #535 under it), the CI's two jobs in containers (ubuntu:26.04), with all 46 tests:
test-mana-restart.pyandtest-loader-debug.pySummary by CodeRabbit
Compatibility
Testing