01f5b4007b
2 Коммитов
| Автор | SHA1 | Сообщение | Дата | |
|---|---|---|---|---|
Jeff Squyres
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520147f209 |
Clean up the Fortran MPI sentinel values per problem reported on the
users mailing list: http://www.open-mpi.org/community/lists/users/2006/07/1680.php Warning: this log message is not for the weak. Read at your own risk. The problem was that we had several variables in Fortran common blocks of various types, but their C counterparts were all of a type equivalent to a fortran double complex. This didn't seem to matter for the compilers that we tested, but we never tested static builds (which is where this problem seems to occur, at least with the Intel compiler: the linker compilains that the variable in the common block in the user's .o file was of one size/alignment but the one in the C library was a different size/alignment). So this patch fixes the sizes/types of the Fortran common block variables and their corresponding C instantiations to be of the same sizes/types. But wait, there's more. We recently introduced a fix for the OSX linker where some C versions of the fortran common block variables (e.g., _ompi_fortran_status_ignore) were not being found when linking ompi_info (!). Further research shows that the code path for ompi_info to require ompi_fortran_status_ignore is, unfortunately, necessary (a quirk of how various components pull in different portions of the code base -- nothing in ompi_info itself requires fortran or MPI knowledge, of course). Hence, the real problem was that there was no code path from ompi_info to the portion of the code base where the C globals corresponding to the Fortran common block variables were instantiated. This is because the OSX linker does not automatically pull in .o files that only contain unintialized global variables; the OSX linker typically only pulls in a .o file from a library if it either has a function that is used or have a global variable that is initialized (that's the short version; lots of details and corner cases omitted). Hence, we changed the global C variables corresponding to the fortran common blocks to be initialized, thereby causing the OSX linker to pull them in automatically -- problem solved. At the same time, we moved the constants to another .c file with a function, just for good measure. However, this didn't really solve the problem: 1. The function in the file with the C versions of the fortran common block variables (ompi/mpi/f77/test_constants_f.c) did not have a code path that was reachable from ompi_info, so the only reason that the constants were found (on OSX) was because they were initialized in the global scope (i.e., causing the OSX compiler to pull in that .o file). 2. Initializing these variable in the global scope causes problems for some linkers where -- once all the size/type problems mentioned above were fixed -- the alignments of fortran common blocks and C global variables do not match (even though the types of the Fortran and C variables match -- wow!). Hence, initializing the C variables would not necessarily match the alignment of what Fortran expected, and the linker would issue a warning (i.e., the alignment warnings referenced in the original post). The solution is two-fold: 1. Move the Fortran variables from test_constants_f.c to ompi/mpi/runtime/ompi_mpi_init.c where there are other global constants that *are* initialized (that had nothing to do with fortran, so the alignment issues described above are not a factor), and therefore all linkers (including the OSX linker) will pull in this .o file and find all the symbols that it needs. 2. Do not initialize the C variables corresponding to the Fortran common blocks in the global scope. Indeed, never initialize them at all (because we never need their *values* - we only check for their *locations*). Since nothing is ever written to these variables (particularly in the global scope), the linker does not see any alignment differences during initialization, but does make both the C and Fortran variables have the same addresses (this method has been working in LAM/MPI for over a decade). There were some comments here in the OMPI code base and in the LAM code base that stated/implied that C variables corresponding to Fortran common blocks had to have the same alignment as the Fortran common blocks (i.e., 16). There were attempts in both code bases to ensure that this was true. However, the attempts were wrong (in both code bases), and I have now read enough Fortran compiler documentation to convince myself that matching alignments is not required (indeed, it's beyond our control). As long as C variables corresponding to Fortran common blocks are not initialized in the global scope, the linker will "figure it out" and adjust the alignment to whatever is required (i.e., the greater of the alignments). Specifically (to counter comments that no longer exist in the OMPI code base but still exist in the LAM code base): - there is no need to make attempts to specially align C variables corresponding to Fortran common blocks - the types and sizes of C variables corresponding to Fortran common blocks should match, but do not need to be on any particular alignment Finally, as a side effect of this effort, I found a bunch of inconsistencies with the intent of status/array_of_statuses parameters. For all the functions that I modified they should be "out" (not inout). This commit was SVN r11057. |
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Jeff Squyres
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02d8a46d5f |
Fix for ticket #89.
* Change the type of Fortan's MPI_STATUSES_IGNORE to double complex so that it will never possibly be mistaken for a real status (i.e., integer(MPI_STATUS_SIZE)), particularly in the F90 bindings. See comment in mpif-common.h explaining this (analogous argument to MPI_ARGVS_NULL for MPI_COMM_SPAWN_MULTIPLE). * Add second interfaces for the following functions that take a double complex (i.e., MPI_STATUSES_IGNORE). This required adding the second interface in mpi-f90-interfaces.h[.sh] and then generating new wrapper functions to call the back-end F77 function for each of these four, so we added 4 new files in ompi/mpi/f90/scripts/ and updated the various Makefile.am's to match: * MPI_TESTALL * MPI_TESTSOME * MPI_WAITALL * MPI_WAITSOME The XSL is now not in sync with the scripts. Although I suppose that that is becoming less and less important (because it does not impact the end user at all -- to be 100% explicit, no release should ever be held up because the XSL is out of sync), but it will probably be important when we go to fix the "large" interface; so it's still worth fixing... for now... This commit was SVN r10281. |