Source tree: The tree where the PMIx source code is located. It is typically the result of expanding an PMIx distribution source code bundle, such as a tarball.
Build tree: The tree where PMIx was built. It is always related to a specific source tree, but may actually be a different tree (since PMIx supports VPATH builds). Specifically, this is the tree where you invoked
make, etc. to build and install PMIx.
Installation tree: The tree where PMIx was installed. It is typically the “prefix” argument given to PMIx’s
configurescript; it is the directory from which you run installed PMIx executables.