1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
|
.. _label-running-dynamic-loading-libmpi:
Dynamically loading ``libmpi`` at runtime
=========================================
If you want to explicitly load Open MPI's shared library ``libmpi`` at
runtime by using ``dlopen()`` from C/C ++ or something like the
``ctypes`` package from Python, extra care is required. The
default configuration of Open MPI uses ``dlopen()`` internally to load
its support components. These components rely on symbols available in
``libmpi``. In order to make the symbols in ``libmpi`` available to
the components loaded by Open MPI at runtime, your application must load
``libmpi`` with the ``RTLD_GLOBAL`` option.
In C/C++, this option is specified as the second parameter to the
POSIX ``dlopen(3)`` function.
When using ``ctypes`` with Python, this can be done with the second
(optional) parameter to ``CDLL()``. For example (shown below in Mac OS
X, where Open MPI's shared library name ends in ``.dylib``; other
operating systems use other suffixes, such as ``.so``):
.. code-block:: python
from ctypes import *
mpi = CDLL('libmpi.0.dylib', RTLD_GLOBAL)
f = pythonapi.Py_GetArgcArgv
argc = c_int()
argv = POINTER(c_char_p)()
f(byref(argc), byref(argv))
mpi.MPI_Init(byref(argc), byref(argv))
# Your MPI program here
mpi.MPI_Finalize()
.. note:: The above is just an example showing dynamic loading. If
you want to use MPI in Python, you are much better off using
`MPI4Py <https://mpi4py.github.io/>`_.
Other scripting languages should have similar options when dynamically
loading shared libraries.
|
