Merge pull request #3075 from oesteban/enh/better-errors-reading-results

ENH: Minimize the number of calls to ``_load_results`` when populating inputs

Author: satra

nipype/pipeline/engine/nodes.py

@@ -9,7 +9,7 @@
                         absolute_import)
 from builtins import range, str, bytes, open
 
-from collections import OrderedDict
+from collections import OrderedDict, defaultdict
 
 import os
 import os.path as op
@@ -510,49 +510,60 @@ def _get_hashval(self):
         return self._hashed_inputs, self._hashvalue
 
     def _get_inputs(self):
-        """Retrieve inputs from pointers to results file
+        """
+        Retrieve inputs from pointers to results files.
 
         This mechanism can be easily extended/replaced to retrieve data from
         other data sources (e.g., XNAT, HTTP, etc.,.)
         """
-        if self._got_inputs:
+        if self._got_inputs:  # Inputs cached
+            return
+
+        if not self.input_source:  # No previous nodes
+            self._got_inputs = True
             return
 
-        logger.debug('Setting node inputs')
+        prev_results = defaultdict(list)
         for key, info in list(self.input_source.items()):
-            logger.debug('input: %s', key)
-            results_file = info[0]
-            logger.debug('results file: %s', results_file)
-            outputs = _load_resultfile(results_file).outputs
+            prev_results[info[0]].append((key, info[1]))
+
+        logger.debug(
+            '[Node] Setting %d connected inputs of node "%s" from %d previous nodes.',
+            len(self.input_source), self.name, len(prev_results))
+
+        for results_fname, connections in list(prev_results.items()):
+            outputs = None
+            try:
+                outputs = _load_resultfile(results_fname).outputs
+            except AttributeError as e:
+                logger.critical('%s', e)
+
             if outputs is None:
                 raise RuntimeError("""\
-Error populating the input "%s" of node "%s": the results file of the source node \
-(%s) does not contain any outputs.""" % (key, self.name, results_file))
-            output_value = Undefined
-            if isinstance(info[1], tuple):
-                output_name = info[1][0]
-                value = getattr(outputs, output_name)
-                if isdefined(value):
-                    output_value = evaluate_connect_function(
-                        info[1][1], info[1][2], value)
-            else:
-                output_name = info[1]
+Error populating the inputs of node "%s": the results file of the source node \
+(%s) does not contain any outputs.""" % (self.name, results_fname))
+
+            for key, conn in connections:
+                output_value = Undefined
+                if isinstance(conn, tuple):
+                    value = getattr(outputs, conn[0])
+                    if isdefined(value):
+                        output_value = evaluate_connect_function(
+                            conn[1], conn[2], value)
+                else:
+                    output_value = getattr(outputs, conn)
+
                 try:
-                    output_value = outputs.trait_get()[output_name]
-                except AttributeError:
-                    output_value = outputs.dictcopy()[output_name]
-            logger.debug('output: %s', output_name)
-            try:
-                self.set_input(key, deepcopy(output_value))
-            except traits.TraitError as e:
-                msg = (
-                    e.args[0], '', 'Error setting node input:',
-                    'Node: %s' % self.name, 'input: %s' % key,
-                    'results_file: %s' % results_file,
-                    'value: %s' % str(output_value),
-                )
-                e.args = ('\n'.join(msg), )
-                raise
+                    self.set_input(key, deepcopy(output_value))
+                except traits.TraitError as e:
+                    msg = (
+                        e.args[0], '', 'Error setting node input:',
+                        'Node: %s' % self.name, 'input: %s' % key,
+                        'results_file: %s' % results_fname,
+                        'value: %s' % str(output_value),
+                    )
+                    e.args = ('\n'.join(msg), )
+                    raise
 
         # Successfully set inputs
         self._got_inputs = True