precomp decorator support

Precomp functions are specified with the @nb.precomp decorator to BudgetItem.calc() methods. The are supplied with the freq array and the ifo struct, their output are supplied as keyword arguments to the wrapped calc(), and their output is cached to prevent re-calculating the same functions multiple time per budget run.

gwinc/nb.py

@@ -220,14 +220,36 @@ class Noise(BudgetItem):
         return self._make_trace(psd=total)
 
     def run(self, **kwargs):
-        """Convenience method to load, update, and return calc traces.
+        """Calculate budget noise and return BudgetTrace object.
 
-        Equivalent of load(), update(), calc_traces() run in sequence.
-        Keyword arguments are passed to update().
+        Roughly the equivalent running load(), update(), and
+        calc_trace() in sequence.  Keyword arguments are passed to the
+        update() method.
+
+        NOTE: The update() method is only run if keyword arguments
+        (`kwargs`) are supplied, or if the `ifo` attribute has
+        changed.
 
         """
         self.load()
         self.update(**kwargs)
+
+        ifo = kwargs.get('ifo', getattr(self, 'ifo'))
+        if ifo:
+            if not hasattr(ifo, '_orig_keys'):
+                logger.debug("new ifo detected")
+                ifo._orig_keys = tuple(k for k, v in ifo.walk())
+                ifo_hash = ifo.hash()
+                kwargs['ifo'] = ifo
+            else:
+                ifo_hash = ifo.hash(ifo._orig_keys)
+                if ifo_hash != getattr(self, '_ifo_hash', 0):
+                    logger.debug("ifo hash change")
+                    kwargs['ifo'] = self.ifo
+            self._ifo_hash = ifo_hash
+        if kwargs:
+            self.update(**kwargs)
+
         return self.calc_trace()