Add regression test for final_gen_send PERSIS_STOP with empty H_rows

libensemble/manager.py

@@ -418,6 +418,9 @@ def _set_resources(self, Work: dict, w: int) -> None:
         If rsets are not assigned, then assign using default mapping
         """
         resource_manager = self.resources.resource_manager  # type: ignore
+        if resource_manager is None:
+            return
+
         rset_req = Work["libE_info"].get("rset_team")
 
         if rset_req is None:

libensemble/tests/unit_tests/test_manager_main.py

@@ -5,10 +5,21 @@
 
 import libensemble.manager as man
 import libensemble.tests.unit_tests.setup as setup
+from libensemble.message_numbers import PERSIS_STOP
 
 libE_specs = {"comms": "local", "gen_on_worker": True}
 
 
+class FakeComm:
+    """Records sent messages instead of transmitting them to a real worker."""
+
+    def __init__(self):
+        self.sent = []
+
+    def send(self, tag, obj):
+        self.sent.append((tag, obj))
+
+
 def test_term_test_1():
     # termination_test should be True when we want to stop
 
@@ -52,7 +63,32 @@ def test_term_test_3():
     assert mgr.term_test()
 
 
+def test_send_work_order_persis_stop_empty_rows():
+    # Regression test: a PERSIS_STOP work order with zero H_rows (e.g. final_gen_send
+    # with nothing left to forward to a persistent gen) must still send the meta-message.
+    # Otherwise, a persistent worker blocked in PersistentSupport.recv() waiting on this
+    # message hangs forever, since nothing would ever be sent to it.
+    hist, sim_specs, gen_specs, exit_criteria, al = setup.hist_setup2()
+    final_libE_specs = dict(libE_specs, final_gen_send=True)
+    fake_wcomm = FakeComm()
+    mgr = man.Manager(hist, final_libE_specs, al, sim_specs, gen_specs, exit_criteria, wcomms=[fake_wcomm])
+
+    work = {
+        "H_fields": ["x"],
+        "persis_info": {},
+        "tag": PERSIS_STOP,
+        "libE_info": {"persistent": True, "H_rows": np.array([], dtype=int)},
+    }
+    mgr._send_work_order(work, 1)
+
+    assert len(fake_wcomm.sent) == 1, "Expected the PERSIS_STOP meta-message to be sent even with zero H_rows"
+    tag, sent_work = fake_wcomm.sent[0]
+    assert tag == PERSIS_STOP
+    assert len(sent_work["libE_info"]["H_rows"]) == 0
+
+
 if __name__ == "__main__":
     test_term_test_1()
     test_term_test_2()
     test_term_test_3()
+    test_send_work_order_persis_stop_empty_rows()