Differences

This shows you the differences between two versions of the page.

--- compiling:mpi [2020/05/14 15:53] – created daniel
+++ compiling:mpi [2020/05/14 16:24] (current) – daniel
@@ Line 3: / Line 3: @@
 ----
+//potfit// does support all common MPI implementations for parallel execution. While the build process for an MPI-enabled build is almost the same as a regular build, there are some minor differences you should be aware of.
+===== Basics =====
+In order to enable MPI support in //potfit// the ''--enable-mpi'' command line option needs to be specified. It will always be assumed that there is an ''mpicc'' command which knows how to handle the current environment properly.
+<wrap round warning 595px center>
+When using ''--enable-mpi'' you cannot specify a compiler with the ''--check-c-compiler'' flag!
+</wrap>
+A command to compile //potfit// with MPI support might look like this:
+<code>./waf configure -i pair -m apot --enable-mpi</code>
+Usually you should see output similar to this:
+<code>
+Checking for 'icc' (C compiler)          : not found
+Checking for 'clang' (C compiler)        : not found
+Checking for 'gcc' (C compiler)          : mpicc
+</code>
+All enabled options will also be listed on the summary of the configuration stage:
+<code>
+potfit has been configured with the following options:
+potential model      = apot
+interaction          = pair
+math library         = mkl
+options              = mpi
+</code>
+===== Selecting the MPI compiler =====
+The selection of the MPI compiler depends on your MPI implementation. For [[https://www.open-mpi.org/|Open MPI]] this behavior is controlled through environment variables, like ''OMPI_CC'', ''OMPI_CFLAGS'' and ''OMPI_LDFLAGS''.
+To switch the compiler you can use this command (OpenMPI):
+<code>OMPI_CC="clang" ./waf configure -i pair -m apot --enable-mpi</code>
+Checking the output, you should see that the ''mpicc'' command has now been identified as a clang compiler:
+<code>
+Checking for 'icc' (C compiler)          : not found
+Checking for 'clang' (C compiler)        : mpicc
+</code>
+To make sure the same value of the environment variables are used for all steps of the //potfit// compilation process please export the variable using you shell.