Ensure the process id to thread id to node id index is maintained. (#200)

Summary:

Currently this map is not set since __ROOT_THREAD__ is not a valid node anymore. We can safely read thr pid and tid against a node id and store in this map.

Differential Revision: D71565563

Author: sanrise

et_replay/execution_trace.py

@@ -358,9 +358,9 @@ def __init__(self, json):
             output_tensors = self.nodes[id].get_output_tensors()
 
             # track the various process and threads we have
-            if x["name"] == "__ROOT_THREAD__":
-                tid = self.nodes[id].tid
-                self.proc_group[pid][tid] = id
+            tid = self.nodes[id].tid
+            # track the various process and threads we have
+            self.proc_group.setdefault(pid, {}).setdefault(tid, []).append(id)
 
             # build tensor reference table
             for t_type, t_id, shape in input_tensors: