Generalize from_pid to find_simulation

This allows searching for a sim by any of its parameters over the
multicate channel.

share/trick/pymods/trick/variable_server.py

@@ -533,7 +533,7 @@ class VariableServer(object):
             # - appending to the variables list while
             #   update_variables is executing does not invalidate
             #   the length check
-            # - izip is bounded by the number of values, and the
+            # - zip is bounded by the number of values, and the
             #   length check ensures there are at least as many
             #   variables as values
             self._variables.append(variable)
@@ -568,11 +568,11 @@ class VariableServer(object):
         self._var_clear()
         # No lock is needed here because:
         # - This assignment is atomic.
-        # - If update_variables has already called izip, the list it is
+        # - If update_variables has already called zip, the list it is
         #   ierating over is unchanged as we're assigning a new list
         #   here instead of clearing the shared reference.
-        # - If update_variables has not yet called izip, when it does,
-        #   izip will return an empty generator, terminating the loop.
+        # - If update_variables has not yet called zip, when it does,
+        #   zip will return an empty generator, terminating the loop.
         self._variables = []
 
     def set_units(self, name, units):
@@ -1029,16 +1029,43 @@ class VariableServer(object):
         self._asynchronous_socket.close()
         self._thread.join()
 
-def from_pid(pid, timeout=None):
+    def __str__(self):
+        return 'VariableServer' + str(self._synchronous_socket.getpeername())
+
+def find_simulation(host=None, port=None, user=None, pid=None,
+                   version=None, sim_directory=None, s_main=None,
+                   input_file=None, tag=None, timeout=None):
     """
-    Connect to the simulation at the given pid. This is done by
-    listening on the multicast channel over which all sims broadcast
-    their existance.
+    Listen for simulations on the multicast channel over which all sims broadcast
+    their existance. Connect to the one that matches the provided arguments that
+    are not None.
+
+    If there are multiple matches, connect to the first one we happen to find.
+    If all arguments are None, connect to the first sim we happen to find.
+    Such matches will be non-deterministic.
 
     Parameters
     ----------
+    host : str
+        Host name of the machine on which the sim is running as reported by
+        Trick.
+    port : int
+        Variable Server port.
+    user : str
+        Simulation process user.
     pid : int
         The sim's process ID.
+    version : str
+        Trick version.
+    sim_directory : str
+        SIM_* directory. If this starts with /, it will be considered an
+        absolute path.
+    s_main : str
+        Filename of the S_main* executeable. Not an absolute path.
+    input_file : str
+        Path to the input file relative to the simDirectory.
+    tag : str
+        Simulation tag.
     timeout : positive float or None
         How long to look for the sim before giving up. Pass None to wait
         indefinitely.
@@ -1046,7 +1073,8 @@ def from_pid(pid, timeout=None):
     Returns
     -------
     VariableServer
-        A VariableServer connected to the sim at pid.
+        A VariableServer connected to the sim matcthing the specified
+        parameters.
 
     Raises
     ------
@@ -1060,9 +1088,18 @@ def from_pid(pid, timeout=None):
     sock.setsockopt(
       socket.IPPROTO_IP,
       socket.IP_ADD_MEMBERSHIP,
-      struct.pack("=4sl", socket.inet_aton('224.3.14.15'), socket.INADDR_ANY))
+      struct.pack('=4sl', socket.inet_aton('224.3.14.15'), socket.INADDR_ANY))
     file_interface = sock.makefile()
 
+    def candidate_matches(candidate):
+        for parameter, candidate_parameter in zip(
+          [host, port, user, pid, sim_directory,
+           s_main, input_file, version, tag],
+          candidate) :
+            if parameter is not None and str(parameter) != candidate_parameter:
+                return False
+        return True
+
     # the socket will clean itself up when it's garbage-collected
     while True:
         if timeout is not None:
@@ -1072,9 +1109,22 @@ def from_pid(pid, timeout=None):
             clock = time.time()
             sock.settimeout(timeout)
 
-        host, port, _, process_id = file_interface.readline().split('\t')[:4]
-        if int(process_id) == int(pid):
-            return VariableServer(host, port)
+        # 0: host
+        # 1: port
+        # 2: user
+        # 3: pid
+        # 4: SIM_*
+        # 5: S_main*
+        # 6: RUN_*
+        # 7: version
+        # 8: tag
+        candidate = file_interface.readline().split('\t')[:9]
+
+        if not str(sim_directory).startswith('/'):
+            candidate[4] = os.path.basename(candidate[4])
+
+        if candidate_matches(candidate):
+            return VariableServer(candidate[0], candidate[1])
 
 def _parse_value(text):
     """