python-control · sawyerbfuller · Nov 6, 2021 · Sep 11, 2021 · Sep 11, 2021 · Sep 12, 2021
diff --git a/control/iosys.py b/control/iosys.py
@@ -1398,7 +1398,164 @@ def set_output_map(self, output_map):
         self.noutputs = output_map.shape[0]
 
 
+    def unused_signals(self):
+        """Find unused subsystem inputs and outputs
+
+        Returns
+        -------
+
+        unused_inputs : dict
+
+          A mapping from tuple of indices (isys, isig) to string
+          '{sys}.{sig}', for all unused subsystem inputs.
+
+        unused_outputs : dict
+
+          A mapping from tuple of indices (isys, isig) to string
+          '{sys}.{sig}', for all unused subsystem outputs.
+
+        """
+        used_sysinp_via_inp = np.nonzero(self.input_map)[0]
+        used_sysout_via_out = np.nonzero(self.output_map)[1]
+        used_sysinp_via_con, used_sysout_via_con = np.nonzero(self.connect_map)
+
+        used_sysinp = set(used_sysinp_via_inp) | set(used_sysinp_via_con)
+        used_sysout = set(used_sysout_via_out) | set(used_sysout_via_con)
+
+        nsubsysinp = sum(sys.ninputs for sys in self.syslist)
+        nsubsysout = sum(sys.noutputs for sys in self.syslist)
+
+        unused_sysinp = sorted(set(range(nsubsysinp)) - used_sysinp)
+        unused_sysout = sorted(set(range(nsubsysout)) - used_sysout)
+
+        inputs = [(isys,isig, f'{sys.name}.{sig}')
+                  for isys, sys in enumerate(self.syslist)
+                  for sig, isig in sys.input_index.items()]
+
+        outputs = [(isys,isig,f'{sys.name}.{sig}')
+                   for isys, sys in enumerate(self.syslist)
+                   for sig, isig in sys.output_index.items()]
+
+        return ({inputs[i][:2]:inputs[i][2]
+                for i in unused_sysinp},
+                {outputs[i][:2]:outputs[i][2]
+                 for i in unused_sysout})
+
+
+    def _find_inputs_by_basename(self, basename):
+        """Find all subsystem inputs matching basename
+
+        Returns
+        -------
+        Mapping from (isys, isig) to '{sys}.{sig}' 
+
+        """
+        return {(isys, isig) : f'{sys.name}.{basename}'
+                for isys, sys in enumerate(self.syslist)
+                for sig, isig in sys.input_index.items()
+                if sig == (basename)}
+
+
+    def _find_outputs_by_basename(self, basename):
+        """Find all subsystem outputs matching basename
+
+        Returns
+        -------
+        Mapping from (isys, isig) to '{sys}.{sig}' 
+
+        """
+        return {(isys, isig) : f'{sys.name}.{basename}'
+                for isys, sys in enumerate(self.syslist)
+                for sig, isig in sys.output_index.items()
+                if sig == (basename)}
+
+
+    def check_unused_signals(self, ignore_inputs=None, ignore_outputs=None):
+        """Check for unused subsystem inputs and outputs
+
+        If any unused inputs or outputs are found, emit a warning.
+
+        Parameters
+        ----------
+        ignore_inputs : list of input-spec
+          Subsystem inputs known to be unused.  input-spec can be any of:
+            'sig', 'sys.sig', (isys, isig), ('sys', isig)
+
+          If the 'sig' form is used, all subsystem inputs with that
+          name are considered ignored.
+
+        ignore_outputs : list of output-spec
+          Subsystem outputs known to be unused.  output-spec can be any of:
+            'sig', 'sys.sig', (isys, isig), ('sys', isig)
+
+          If the 'sig' form is used, all subsystem outputs with that
+          name are considered ignored.
+
+        """
+
+        if ignore_inputs is None:
+            ignore_inputs = []
+
+        if ignore_outputs is None:
+            ignore_outputs = []
+
+        unused_inputs, unused_outputs = self.unused_signals()
+
+        # (isys, isig) -> signal-spec
+        ignore_input_map = {}
+        for ignore_input in ignore_inputs:
+            if isinstance(ignore_input, str) and '.' not in ignore_input:
+                ignore_idxs = self._find_inputs_by_basename(ignore_input)
+                if not ignore_idxs:
+                    raise ValueError(f"Couldn't find ignored input {ignore_input} in subsystems")
+                ignore_input_map.update(ignore_idxs)
+            else:
+                ignore_input_map[self._parse_signal(ignore_input, 'input')[:2]] = ignore_input
+
+        # (isys, isig) -> signal-spec
+        ignore_output_map = {}
+        for ignore_output in ignore_outputs:
+            if isinstance(ignore_output, str) and '.' not in ignore_output:
+                ignore_found = self._find_outputs_by_basename(ignore_output)
+                if not ignore_found:
+                    raise ValueError(f"Couldn't find ignored output {ignore_output} in subsystems")
+                ignore_output_map.update(ignore_found)
+            else:
+                ignore_output_map[self._parse_signal(ignore_output, 'output')[:2]] = ignore_output
+
+        dropped_inputs = set(unused_inputs) - set(ignore_input_map)
+        dropped_outputs = set(unused_outputs) - set(ignore_output_map)
+
+        used_ignored_inputs = set(ignore_input_map) - set(unused_inputs)
+        used_ignored_outputs =  set(ignore_output_map) - set(unused_outputs)
+
+        if dropped_inputs:
+            msg = ('Unused input(s) in InterconnectedSystem: '
+                   + '; '.join(f'{inp}={unused_inputs[inp]}'
+                               for inp in dropped_inputs))
+            warn(msg)
+
+        if dropped_outputs:
+            msg = ('Unused output(s) in InterconnectedSystem: '
+                   + '; '.join(f'{out} : {unused_outputs[out]}'
+                               for out in dropped_outputs))
+            warn(msg)
+
+        if used_ignored_inputs:
+            msg = ('Input(s) specified as ignored is (are) used: '
+                   + '; '.join(f'{inp} : {ignore_input_map[inp]}'
+                               for inp in used_ignored_inputs))
+            warn(msg)
+
+        if used_ignored_outputs:
+            msg = ('Output(s) specified as ignored is (are) used: '
+                   + '; '.join(f'{out}={ignore_output_map[out]}'
+                               for out in used_ignored_outputs))
+            warn(msg)
+
+
 class LinearICSystem(InterconnectedSystem, LinearIOSystem):
+
     """Interconnection of a set of linear input/output systems.
 
     This class is used to implement a system that is an interconnection of
@@ -2020,7 +2177,9 @@ def tf2io(*args, **kwargs):
 # Function to create an interconnected system
 def interconnect(syslist, connections=None, inplist=[], outlist=[],
                  inputs=None, outputs=None, states=None,
-                 params={}, dt=None, name=None, **kwargs):
+                 params={}, dt=None, name=None,
+                 check_unused=True, ignore_inputs=None, ignore_outputs=None,
+                 **kwargs):
     """Interconnect a set of input/output systems.
 
     This function creates a new system that is an interconnection of a set of
@@ -2145,6 +2304,32 @@ def interconnect(syslist, connections=None, inplist=[], outlist=[],
         System name (used for specifying signals). If unspecified, a generic
         name <sys[id]> is generated with a unique integer id.
 
+    check_unused : bool
+        If True, check for unused sub-system signals.  This check is
+        not done if connections is False, and neither input nor output
+        mappings are specified.
+
+    ignore_inputs : list of input-spec
+        A list of sub-system inputs known not to be connected.  This is
+        *only* used in checking for unused signals, and does not
+        disable use of the input.
+
+        Besides the usual input-spec forms (see `connections`), an
+        input-spec can be just the signal base name, in which case all
+        signals from all sub-systems with that base name are
+        considered ignored.
+
+    ignore_outputs : list of output-spec
+        A list of sub-system outputs known not to be connected.  This
+        is *only* used in checking for unused signals, and does not
+        disable use of the output.
+
+        Besides the usual output-spec forms (see `connections`), an
+        output-spec can be just the signal base name, in which all
+        outputs from all sub-systems with that base name are
+        considered ignored.
+
+
     Example
     -------
     >>> P = control.LinearIOSystem(
@@ -2199,6 +2384,17 @@ def interconnect(syslist, connections=None, inplist=[], outlist=[],
     inputs = _parse_signal_parameter(inputs, 'input', kwargs)
     outputs =  _parse_signal_parameter(outputs, 'output', kwargs, end=True)
 
+    if not check_unused and (ignore_inputs or ignore_outputs):
+        raise ValueError('check_unused is False, but either '
+                         + 'ignore_inputs or ignore_outputs non-empty')
+
+    if (connections is False
+        and not inplist and not outlist
+        and not inputs and not outputs):
+        # user has disabled auto-connect, and supplied neither input
+        # nor output mappings; assume they know what they're doing
+        check_unused = False
+
     # If connections was not specified, set up default connection list
     if connections is None:
         # For each system input, look for outputs with the same name
@@ -2211,7 +2407,11 @@ def interconnect(syslist, connections=None, inplist=[], outlist=[],
                         connect.append(output_sys.name + "." + input_name)
                 if len(connect) > 1:
                     connections.append(connect)
+
+        auto_connect = True
+
     elif connections is False:
+        check_unused = False
         # Use an empty connections list
         connections = []
 
@@ -2282,6 +2482,10 @@ def interconnect(syslist, connections=None, inplist=[], outlist=[],
         inputs=inputs, outputs=outputs, states=states,
         params=params, dt=dt, name=name)
 
+
+    # check for implicity dropped signals
+    if check_unused:
+        newsys.check_unused_signals(ignore_inputs, ignore_outputs)
     # If all subsystems are linear systems, maintain linear structure
     if all([isinstance(sys, LinearIOSystem) for sys in syslist]):
         return LinearICSystem(newsys, None)

diff --git a/control/tests/iosys_test.py b/control/tests/iosys_test.py
@@ -9,6 +9,7 @@
 """
 
 from __future__ import print_function
+import re
 
 import numpy as np
 import pytest
@@ -1396,3 +1397,139 @@ def secord_update(t, x, u, params={}):
 def secord_output(t, x, u, params={}):
     """Second order system dynamics output"""
     return np.array([x[0]])
+
+
+def test_interconnect_unused_input():
+    # test that warnings about unused inputs are reported, or not,
+    # as required
+    g = ct.LinearIOSystem(ct.ss(-1,1,1,0),
+                          inputs=['u'],
+                          outputs=['y'],
+                          name='g')
+
+    s = ct.summing_junction(inputs=['r','-y','-n'],
+                            outputs=['e'],
+                            name='s')
+
+    k = ct.LinearIOSystem(ct.ss(0,10,2,0),
+                          inputs=['e'],
+                          outputs=['u'],
+                          name='k')
+
+    with pytest.warns(UserWarning, match=r"Unused input\(s\) in InterconnectedSystem"):
+        h = ct.interconnect([g,s,k],
+                            inputs=['r'],
+                            outputs=['y'])
+
+    with pytest.warns(None) as record:
+        # no warning if output explicitly ignored, various argument forms
+        h = ct.interconnect([g,s,k],
+                            inputs=['r'],
+                            outputs=['y'],
+                            ignore_inputs=['n'])
+
+        h = ct.interconnect([g,s,k],
+                            inputs=['r'],
+                            outputs=['y'],
+                            ignore_inputs=['s.n'])
+
+        # no warning if auto-connect disabled
+        h = ct.interconnect([g,s,k],
+                            connections=False)
+
+        #https://docs.pytest.org/en/6.2.x/warnings.html#recwarn
+        for r in record:
+            # strip out matrix warnings
+            if re.match(r'.*matrix subclass', str(r.message)):
+                continue
+            print(r.message)
+            pytest.fail(f'Unexpected warning: {r.message}')
+
+
+    # warn if explicity ignored input in fact used
+    with pytest.warns(UserWarning, match=r"Input\(s\) specified as ignored is \(are\) used:") as record:
+        h = ct.interconnect([g,s,k],
+                            inputs=['r'],
+                            outputs=['y'],
+                            ignore_inputs=['u','n'])
+
+    with pytest.warns(UserWarning, match=r"Input\(s\) specified as ignored is \(are\) used:") as record:
+        h = ct.interconnect([g,s,k],
+                            inputs=['r'],
+                            outputs=['y'],
+                            ignore_inputs=['k.e','n'])
+
+    # error if ignored signal doesn't exist
+    with pytest.raises(ValueError):
+        h = ct.interconnect([g,s,k],
+                            inputs=['r'],
+                            outputs=['y'],
+                            ignore_inputs=['v'])
+
+
+def test_interconnect_unused_output():
+    # test that warnings about ignored outputs are reported, or not,
+    # as required
+    g = ct.LinearIOSystem(ct.ss(-1,1,[[1],[-1]],[[0],[1]]),
+                          inputs=['u'],
+                          outputs=['y','dy'],
+                          name='g')
+
+    s = ct.summing_junction(inputs=['r','-y'],
+                            outputs=['e'],
+                            name='s')
+
+    k = ct.LinearIOSystem(ct.ss(0,10,2,0),
+                          inputs=['e'],
+                          outputs=['u'],
+                          name='k')
+
+    with pytest.warns(UserWarning, match=r"Unused output\(s\) in InterconnectedSystem:") as record:
+        h = ct.interconnect([g,s,k],
+                            inputs=['r'],
+                            outputs=['y'])
+
+
+    # no warning if output explicitly ignored
+    with pytest.warns(None) as record:
+        h = ct.interconnect([g,s,k],
+                            inputs=['r'],
+                            outputs=['y'],
+                            ignore_outputs=['dy'])
+
+        h = ct.interconnect([g,s,k],
+                            inputs=['r'],
+                            outputs=['y'],
+                            ignore_outputs=['g.dy'])
+
+        # no warning if auto-connect disabled
+        h = ct.interconnect([g,s,k],
+                            connections=False)
+
+        #https://docs.pytest.org/en/6.2.x/warnings.html#recwarn
+        for r in record:
+            # strip out matrix warnings
+            if re.match(r'.*matrix subclass', str(r.message)):
+                continue
+            print(r.message)
+            pytest.fail(f'Unexpected warning: {r.message}')
+
+    # warn if explicity ignored output in fact used
+    with pytest.warns(UserWarning, match=r"Output\(s\) specified as ignored is \(are\) used:"):
+        h = ct.interconnect([g,s,k],
+                            inputs=['r'],
+                            outputs=['y'],
+                            ignore_outputs=['dy','u'])
+
+    with pytest.warns(UserWarning, match=r"Output\(s\) specified as ignored is \(are\) used:"):
+        h = ct.interconnect([g,s,k],
+                            inputs=['r'],
+                            outputs=['y'],
+                            ignore_outputs=['dy', ('k.u')])
+
+    # error if ignored signal doesn't exist
+    with pytest.raises(ValueError):
+        h = ct.interconnect([g,s,k],
+                            inputs=['r'],
+                            outputs=['y'],
+                            ignore_outputs=['v'])