https://github.com/technologicat/mpi_shim

MPI support wrapper for optional dependency on mpi4py
https://github.com/technologicat/mpi_shim

mpi mpi4py numpy optional python python2 python27 python3 python34 wrapper

Last synced: about 1 month ago
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MPI support wrapper for optional dependency on mpi4py

• Host: GitHub
• URL: https://github.com/technologicat/mpi_shim
• Owner: Technologicat
• License: bsd-2-clause
• Created: 2017-04-26T11:38:23.000Z (almost 8 years ago)
• Default Branch: master
• Last Pushed: 2017-04-26T11:40:34.000Z (almost 8 years ago)
• Last Synced: 2024-11-19T05:05:51.582Z (3 months ago)
• Topics: mpi, mpi4py, numpy, optional, python, python2, python27, python3, python34, wrapper
• Language: Python
• Size: 3.91 KB
• Stars: 0
• Watchers: 3
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • Changelog: CHANGELOG.md
  • License: LICENSE.md

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README

        
## mpi_shim

MPI support wrapper for optional dependency on mpi4py

### Introduction

This module is designed to be copied into projects that optionally depend on MPI, to unify handling of MPI and non-MPI cases.

To load MPI, import this module. The module can always be imported, regardless of whether `mpi4py` is installed. The availability of the `mpi4py` library can then be queried at runtime using `mpi_shim.has_mpi()`.

Some rudimentary wrappers (`get_size()`, `get_rank()`, `get_comm_world()`) are provided; all the rest should be done directly via `mpi4py`, and only if `has_mpi()` returns True. This way, the same code can run both with and without MPI.

Also provided is `gather_varlength_array()`, a buffer-based fast gather for rank-1 NumPy arrays of varying lengths (like `gatherv`, but determining the sizes automatically).

### Example

Based on [http://mpi4py.scipy.org/docs/usrman/tutorial.html](http://mpi4py.scipy.org/docs/usrman/tutorial.html):

```python

import mpi_shim

MPI    = mpi_shim.get_mpi()         # either a reference to mpi4py.MPI, or None if n/a

nprocs = mpi_shim.get_size()        # actual value from mpi4py, or 1    if n/a

my_id  = mpi_shim.get_rank()        # actual value from mpi4py, or 0    if n/a

comm   = mpi_shim.get_comm_world()  # actual value from mpi4py, or None if n/a

# The rest works as usual:

data = (my_id+1)**2  # 

if MPI is not None:

   data = comm.gather(data, root=0)

if my_id == 0:

   for i in range(nprocs):

       assert data[i] == (i+1)**2

else:

   assert data is None

```

### License

[BSD](LICENSE.md). Copyright 2012-2017 Juha Jeronen and University of Jyväskylä.