https://github.com/boostorg/mpi/issues/179
https://github.com/boostorg/mpi/commit/7c6b9c1be2eba1bf65271adee11683d0e9976ff2

From: Alain Miniussi <alain.miniussi@oca.eu>
Date: Mon, 10 Aug 2026 21:17:53 +0200
Subject: [PATCH] Fixes #179.

Boost.Python indexing suites instantiate code paths requiring stored
types to be equality comparable.

`boost::mpi::python::request_with_value` did not provide an
`operator==`, causing compilation failures.

Add the missing comparison operator and keep existing tests passing.

This is similar to other Boost.Python requirements already documented
in `py_nonblocking.hpp`.
--- a/libs/mpi/src/python/py_request.cpp
+++ b/libs/mpi/src/python/py_request.cpp
@@ -64,6 +64,10 @@ const object python::request_with_value::wrap_test()
     return object();
 }
 
+bool operator==(python::request_with_value const&, python::request_with_value const&) {
+  PyErr_SetString(PyExc_NotImplementedError, "mpi requests are not comparable");
+  throw error_already_set();
+}
 
 namespace boost { namespace mpi { namespace python {
   
--- a/libs/mpi/src/python/request_with_value.hpp
+++ b/libs/mpi/src/python/request_with_value.hpp
@@ -65,7 +65,12 @@ namespace boost { namespace mpi { namespace python {
       friend request_with_value communicator_irecv_content(
           const communicator&, int, int, content&);
   };
-
+      
+  // FIXME: requests are not comparable, thus this operator makes no sense.
+  // Unfortunately, indexing_suites insist on having __contains__ available.
+  // Just make it error out for now.
+  bool
+  operator==(request_with_value const& ,request_with_value const&);
 } } }
 
 #endif