Lazily compute structure factor

Instead of computing the structure factor every time a property of the
material changes, flag the structure factor as invalid, and only re-compute
it if it is requested.

This significantly speeds up interaction with the lattice parameter, such
as with the PT sliders.

Signed-off-by: Patrick Avery <[email protected]>

hexrd/material/crystallography.py

@@ -700,6 +700,9 @@ def __init__(self,
             raise RuntimeError('have unparsed keyword arguments with keys: '
                                + str(list(kwargs.keys())))
 
+        # This is only used to calculate the structure factor if invalidated
+        self.__unitcell = None
+
         self.__calc()
 
         return
@@ -935,7 +938,27 @@ def set_wavelength(self, wavelength):
 
     wavelength = property(get_wavelength, set_wavelength, None)
 
+    def invalidate_structure_factor(self, unitcell):
+        # It can be expensive to compute the structure factor, so provide the
+        # option to just invalidate it, while providing a unit cell, so that
+        # it can be lazily computed from the unit cell.
+        self.__structFact = None
+        self._powder_intensity = None
+        self.__unitcell = unitcell
+
+    def _compute_sf_if_needed(self):
+        any_invalid = (
+            self.__structFact is None or
+            self._powder_intensity is None
+        )
+        if any_invalid and self.__unitcell is not None:
+            # Compute the structure factor first.
+            # This can be expensive to do, so we lazily compute it when needed.
+            hkls = self.getHKLs(allHKLs=True)
+            self.set_structFact(self.__unitcell.CalcXRSF(hkls))
+
     def get_structFact(self):
+        self._compute_sf_if_needed()
         return self.__structFact[~self.exclusions]
 
     def set_structFact(self, structFact):
@@ -953,6 +976,7 @@ def set_structFact(self, structFact):
 
     @property
     def powder_intensity(self):
+        self._compute_sf_if_needed()
         return self._powder_intensity[~self.exclusions]
 
     @staticmethod

hexrd/material/material.py

@@ -226,7 +226,7 @@ def __init__(
             self.reset_v0()
 
         self._newPdata()
-        self.update_structure_factor()
+        self.invalidate_structure_factor()
 
     def __str__(self):
         """String representation"""
@@ -291,7 +291,7 @@ def _newUnitcell(self):
     def _hkls_changed(self):
         # Call this when something happens that changes the hkls...
         self._newPdata()
-        self.update_structure_factor()
+        self.invalidate_structure_factor()
 
     def _newPdata(self):
         """Create a new plane data instance if the hkls have changed"""
@@ -405,10 +405,8 @@ def enable_hkls_below_tth(self, tth_threshold=90.0):
 
         self._pData.exclusions = dflt_excl
 
-    def update_structure_factor(self):
-        hkls = self.planeData.getHKLs(allHKLs=True)
-        sf = self.unitcell.CalcXRSF(hkls)
-        self.planeData.set_structFact(sf)
+    def invalidate_structure_factor(self):
+        self.planeData.invalidate_structure_factor(self.unitcell)
 
     def compute_powder_overlay(
         self, ttharray=np.linspace(0, 80, 2000), fwhm=0.25, scale=1.0
@@ -1268,7 +1266,7 @@ def charge(self, vals):
 
         self._charge = vals
         # self._newUnitcell()
-        # self.update_structure_factor()
+        # self.invalidate_structure_factor()
 
     @property
     def absorption_length(self):
@@ -1390,7 +1388,7 @@ def _set_atomdata(self, atomtype, atominfo, U, charge):
         self.charge = charge
 
         self._newUnitcell()
-        self.update_structure_factor()
+        self.invalidate_structure_factor()
 
     #
     #  ========== Methods