squash! Add wall-time step timers to Simulator

Having separate build and connect methods didn't seem to make
sense, especially because connect depended on build and other
methods depended on either connect or build and sometimes it
raised an error if one wasn't called, and other times it would
just call it. With the changes in this commit, we just have a
`connect` method which does the build and connect (it could
be called `build`, but the `connected` property makes more sense,
and it would be weird to set `connected` with `build`).
If we expect to be connected and aren't, we raise an error.

nengo_loihi/hardware/interface.py

@@ -53,6 +53,7 @@ class HardwareInterface:
         Defaults to one block and one input per core on a single chip.
     """
 
+    connection_retries = 10
     min_nxsdk_version = LooseVersion("0.8.7")
     max_nxsdk_version = LooseVersion("0.9.0")
     channel_packet_elements = 64  # size of channel packets in int32s
@@ -105,8 +106,9 @@ def __enter__(self):
             raise SimulationError(
                 "Loihi interface has been closed and cannot be reopened."
             )
-        if not self.is_built:
-            self.build()
+
+        if not self.connected:
+            self.connect()
         return self
 
     def __exit__(self, exc_type, exc_value, traceback):
@@ -137,10 +139,14 @@ def _iter_probes(self):
                 yield probe
 
     @property
-    def is_built(self):
-        return self.nxsdk_board is not None
+    def connected(self):
+        return self.nxsdk_board is not None and d_func(
+            self.nxsdk_board, b"ZXhlY3V0b3I=", b"aGFzU3RhcnRlZA=="
+        )
+
+    def connect(self):
+        """Builds internal data structures and connects to the board."""
 
-    def build(self):
         assert self.nxsdk_board is None, "Cannot rebuild model"
 
         self.pes_error_scale = getattr(self.model, "pes_error_scale", 1.0)
@@ -167,11 +173,22 @@ def build(self):
         if self.use_snips:
             self.create_io_snip()
 
-    def run_steps(self, steps, blocking=True):
-        if not self.is_built:
-            self.build()
+        # --- connect to the board
+        logger.info("Connecting to Loihi, max attempts: %d", self.connection_retries)
+        for i in range(self.connection_retries):
+            try:
+                d_func(self.nxsdk_board, b"c3RhcnQ=")
+                if self.connected:
+                    break
+            except Exception as e:
+                logger.warning("Connection error: %s", e)
+                time.sleep(1)
+                logger.info("Retrying, attempt %d", i + 1)
+        else:
+            raise SimulationError("Could not connect to the board")
 
-        self.connect()  # returns immediately if already connected
+    def run_steps(self, steps, blocking=True):
+        assert self.connected, "Interface is not built"
 
         # start the board running the desired number of steps
         d_get(self.nxsdk_board, b"cnVu")(steps, **{d(b"YVN5bmM="): not blocking})
@@ -395,31 +412,6 @@ def host2chip(self, spikes, errors):
     def wait_for_completion(self):
         d_func(self.nxsdk_board, b"ZmluaXNoUnVu")
 
-    def is_connected(self):
-        return self.nxsdk_board is not None and d_func(
-            self.nxsdk_board, b"ZXhlY3V0b3I=", b"aGFzU3RhcnRlZA=="
-        )
-
-    def connect(self, attempts=10):
-        if not self.is_built:
-            raise SimulationError("Must build model before running")
-
-        if self.is_connected():
-            return
-
-        logger.info("Connecting to Loihi, max attempts: %d", attempts)
-        for i in range(attempts):
-            try:
-                d_func(self.nxsdk_board, b"c3RhcnQ=")
-                if self.is_connected():
-                    break
-            except Exception as e:
-                logger.warning("Connection error: %s", e)
-                time.sleep(1)
-                logger.info("Retrying, attempt %d", i + 1)
-        else:
-            raise SimulationError("Could not connect to the board")
-
     def close(self):
         if self.host_socket is not None and self.host_socket_connected:
             # send -1 to signal host/chip that we're done
@@ -477,8 +469,7 @@ def get_probe_output(self, probe):
         return self._filter_probe(probe, data)
 
     def create_io_snip(self):
-        # snips must be created before connecting
-        assert not self.is_connected(), "still connected"
+        assert not self.connected, "snips must be created before connecting"
 
         snips_dir = os.path.join(os.path.dirname(__file__), "snips")
         env = jinja2.Environment(

nengo_loihi/hardware/tests/test_interface.py

@@ -8,7 +8,8 @@
 from nengo_loihi.hardware import interface as hardware_interface
 from nengo_loihi.hardware.allocators import OneToOne
 from nengo_loihi.hardware.builder import build_board
-from nengo_loihi.nxsdk_obfuscation import d_set
+from nengo_loihi.hardware.nxsdk_shim import NxsdkBoard
+from nengo_loihi.nxsdk_obfuscation import d
 
 
 class MockNxsdk:
@@ -95,17 +96,13 @@ def test_builder_poptype_errors():
 
 
 @pytest.mark.target_loihi
-def test_interface_connection_errors(Simulator):
+def test_interface_connection_errors(Simulator, monkeypatch):
     with nengo.Network() as net:
         nengo.Ensemble(2, 1)
 
-    # test unbuilt model error
+    # test opening closed interface error
     sim = Simulator(net)
     interface = sim.sims["loihi"]
-    with pytest.raises(SimulationError, match="build.*before running"):
-        interface.connect()
-
-    # test opening closed interface error
     interface.close()
     with pytest.raises(SimulationError, match="cannot be reopened"):
         with interface:
@@ -116,12 +113,11 @@ def test_interface_connection_errors(Simulator):
     def start(*args, **kwargs):
         raise Exception("Mock failure to connect")
 
-    with Simulator(net) as sim:
-        interface = sim.sims["loihi"]
-        d_set(interface.nxsdk_board, b"c3RhcnQ=", val=start)
+    monkeypatch.setattr(NxsdkBoard, d(b"c3RhcnQ="), start)
 
-        with pytest.raises(SimulationError, match="[Cc]ould not connect"):
-            interface.connect(attempts=1)
+    with pytest.raises(SimulationError, match="[Cc]ould not connect"):
+        with Simulator(net):
+            pass
 
 
 @pytest.mark.target_loihi

nengo_loihi/simulator.py

@@ -408,11 +408,6 @@ def __init__(self, model, sims, precompute, timers):
         self.loihi = sims.get("loihi", None)
 
         if self.loihi is not None:
-            # build and connect outside run_steps
-            if not self.loihi.is_built:
-                self.loihi.build()
-            self.loihi.connect()
-
             run_steps = {
                 (
                     True,