User Migration Guide: 1.8.x and v1.10.x to v2.0.0

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Open MPI User Migration Guide

Users should not treat this wiki page as definitive (YET). Please check back later.

(this content will likely end up being on the main Open MPI web site -- not on this wiki -- and linked to from https://www.open-mpi.org/software/ompi/v2.x/)

User-Noticeable changes

I.e., things that may prevent users from simply re-compiling / re-mpirun'ing their existing MPI app.

• mpirun -np behavior
• OMPIO is now the default (not ROMIO): but ROMIO is still the default for Lustre
• MPI C++ bindings are disabled by default
• Not ABI compatible with v1.8/v1.10 / describe the new version number scheme
• ...more?

New features

• Launch scalability improvements (i.e., support for PMIx)
• Lots of improvements to MPI RMA
• Improved support for MPI_THREAD_MULTIPLE (when configured with --enable-mpi-thread-multiple)
• ompi_info pretty print improvements
• UCX support
• PLFS support (via OMPIO)
• Better Cray build / SLURM support
• Better infrastructure for patch support
• ...more?

Removed support

• OS X Leopard
• Cray XT
• VampirTrace
• Myrinet MX / Open-MX
• coll:ml module
• Alpha processors
• --enable-mpi-profiling option
• Checkpoint / restart
• ...more?

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