Add workaround for MPICH 4.2.0

See: https://github.com/pmodels/mpich/issues/6946

Reviewed-by: Aleix Roca Nonell <aleix.rocanonell@bsc.es>

pkgs/mpich-fix-hwtopo.patch

@@ -0,0 +1,36 @@
+diff --git a/src/util/mpir_hwtopo.c b/src/util/mpir_hwtopo.c
+index 33e88bc..ee3641c 100644
+--- a/src/util/mpir_hwtopo.c
++++ b/src/util/mpir_hwtopo.c
+@@ -200,18 +200,6 @@ int MPII_hwtopo_init(void)
+ #ifdef HAVE_HWLOC
+     bindset = hwloc_bitmap_alloc();
+     hwloc_topology_init(&hwloc_topology);
+-    char *xmlfile = MPIR_pmi_get_jobattr("PMI_hwloc_xmlfile");
+-    if (xmlfile != NULL) {
+-        int rc;
+-        rc = hwloc_topology_set_xml(hwloc_topology, xmlfile);
+-        if (rc == 0) {
+-            /* To have hwloc still actually call OS-specific hooks, the
+-             * HWLOC_TOPOLOGY_FLAG_IS_THISSYSTEM has to be set to assert that the loaded
+-             * file is really the underlying system. */
+-            hwloc_topology_set_flags(hwloc_topology, HWLOC_TOPOLOGY_FLAG_IS_THISSYSTEM);
+-        }
+-        MPL_free(xmlfile);
+-    }
+
+     hwloc_topology_set_io_types_filter(hwloc_topology, HWLOC_TYPE_FILTER_KEEP_ALL);
+     if (!hwloc_topology_load(hwloc_topology)) 
+
+--- a/src/mpi/init/local_proc_attrs.c
++++ b/src/mpi/init/local_proc_attrs.c
+@@ -79,10 +79,6 @@ int MPII_init_local_proc_attrs(int *p_thread_required)
+     /* Set the number of tag bits. The device may override this value. */
+     MPIR_Process.tag_bits = MPIR_TAG_BITS_DEFAULT;
+
+-    char *requested_kinds = MPIR_pmi_get_jobattr("PMI_mpi_memory_alloc_kinds");
+-    MPIR_get_supported_memory_kinds(requested_kinds, &MPIR_Process.memory_alloc_kinds);
+-    MPL_free(requested_kinds);
+-
+     return mpi_errno;
+ }

pkgs/overlay.nix

@@ -11,6 +11,10 @@ final: prev:
       paths = [ pmix.dev pmix.out ];
     };
   in prev.mpich.overrideAttrs (old: {
+    patches = [
+      # See https://github.com/pmodels/mpich/issues/6946
+      ./mpich-fix-hwtopo.patch
+    ];
     buildInput = old.buildInputs ++ [
       libfabric
       pmixAll