Extending Python with C: Cannot find MPI library
Spectrum
spectrumdt at gmail.com
Thu Jun 19 10:16:57 EDT 2008
On Jun 19, 2:10 pm, Jeroen Ruigrok van der Werven <asmo... at in-
nomine.org> wrote:
> -On [20080619 13:53], Spectrum (spectru... at gmail.com) wrote:
>
> > ImportError: /big/School/Cluster/Opgave03/ctest.so: undefined
> >symbol: ompi_mpi_comm_world
> > [ore at localhost Opgave03]$
>
> > Can anyone suggest anything? Can I get MPI to work in Python?
>
> Sounds like a typical case of not specifying any -L and/or -l options. In
> this case the ctest.so module has an undefined reference to the symbol
> ompi_mpi_comm_world and cannot resolve it. So either it was not linked
> properly or the loader cannot find the required library.
>
> Apply nm -D and ldd to the .so and see what ails.
Thanks for the reply.
It is very likely that I am not compiling properly. I am a sucky C
programmer.
The commands you recommended give the following output:
[ore at localhost Opgave03]$ nm -D ctest.so
U MPI_Comm_rank
U MPI_Finalize
U MPI_Init
w _Jv_RegisterClasses
000018cc A __bss_start
w __cxa_finalize
w __gmon_start__
U __printf_chk
000018cc A _edata
000018d4 A _end
000006c4 T _fini
00000414 T _init
00000600 T hello
00000650 T main
U ompi_mpi_comm_world
000005b0 T rank
[ore at localhost Opgave03]$
[ore at localhost Opgave03]$
[ore at localhost Opgave03]$ ldd ctest.so
linux-gate.so.1 => (0x00110000)
libpython2.5.so.1.0 => /usr/lib/libpython2.5.so.1.0
(0x00113000)
libpthread.so.0 => /lib/libpthread.so.0 (0x0025a000)
libc.so.6 => /lib/libc.so.6 (0x00342000)
libdl.so.2 => /lib/libdl.so.2 (0x00273000)
libutil.so.1 => /lib/libutil.so.1 (0x00278000)
libm.so.6 => /lib/libm.so.6 (0x0027c000)
/lib/ld-linux.so.2 (0x00325000)
[ore at localhost Opgave03]$
The same commands, when applied to the mpicc-compiled, correctly-
functioning C program (in this case just named 'a.out') give this:
[ore at localhost Opgave03]$ ./a.out
Hello, World. I am process 0.
[ore at localhost Opgave03]$ nm -D a.out
U MPI_Comm_rank
U MPI_Finalize
U MPI_Init
08048818 R _IO_stdin_used
w _Jv_RegisterClasses
080499fc A __bss_start
080499f8 D __data_start
w __gmon_start__
08048750 T __libc_csu_fini
08048760 T __libc_csu_init
U __libc_start_main
080499fc A _edata
08049b10 A _end
080487f8 T _fini
08048814 R _fp_hw
08048560 T _init
080485f0 T _start
080499f8 W data_start
080486f9 T hello
0804871f T main
08049a00 B ompi_mpi_comm_world
U printf
080486c4 T rank
[ore at localhost Opgave03]$ ldd a.out
linux-gate.so.1 => (0x00110000)
libmpi.so.0 => /usr/lib/openmpi/1.2.4-gcc/libmpi.so.0
(0x0042f000)
libopen-rte.so.0 => /usr/lib/openmpi/1.2.4-gcc/libopen-
rte.so.0 (0x003d4000)
libopen-pal.so.0 => /usr/lib/openmpi/1.2.4-gcc/libopen-
pal.so.0 (0x00344000)
libdl.so.2 => /lib/libdl.so.2 (0x00df0000)
libnsl.so.1 => /lib/libnsl.so.1 (0x003b9000)
libutil.so.1 => /lib/libutil.so.1 (0x004d8000)
libm.so.6 => /lib/libm.so.6 (0x0025c000)
libpthread.so.0 => /lib/libpthread.so.0 (0x00287000)
libc.so.6 => /lib/libc.so.6 (0x004dc000)
/lib/ld-linux.so.2 (0x00325000)
[ore at localhost Opgave03]$
I don't know how to interpret these, so can I get some more advice?
Thanks in advance.
- Claus Appel
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