set UCX_TLS in impi with UCX

easybuild/easyblocks/i/impi.py

@@ -41,11 +41,11 @@
 from easybuild.framework.easyconfig import CUSTOM
 from easybuild.tools.build_log import EasyBuildError
 from easybuild.tools.filetools import apply_regex_substitutions, change_dir, extract_file, mkdir, write_file
+from easybuild.tools.modules import get_software_root
 from easybuild.tools.run import run_cmd
 from easybuild.tools.systemtools import get_shared_lib_ext
 from easybuild.tools.toolchain.mpi import get_mpi_cmd_template
 
-
 class EB_impi(IntelBase):
     """
     Support for installing Intel MPI library
@@ -313,4 +313,11 @@ def make_module_extra(self, *args, **kwargs):
             # -fc also works, but -f90 takes precedence
             txt += self.module_generator.set_alias('mpiifort', 'mpiifort -f90=ifort')
 
+        # set environment variable UCX_TLS to 'all', this will work in all setups
+        # needed with UCX regardless of the transports available (even without a Mellanox HCA)
+        # since impi v2019.8, the MLX provider works without UCX_TLS, but setting it does not hurt
+        ucx_root = get_software_root('UCX')
+        if ucx_root:
+            txt += self.module_generator.set_environment('UCX_TLS', 'all')
+
         return txt