Transposing pinMgFluxes so that the leading dimension represents pin index

armi/physics/neutronics/parameters.py

@@ -163,7 +163,7 @@ def _getNeutronicsBlockParams():
             "pinMgFluxes",
             units=f"n/{units.CM}^2/{units.SECONDS}",
             description="""
-            The block-level pin multigroup fluxes. pinMgFluxes[g][i] represents the flux in group g
+            The block-level pin multigroup fluxes. pinMgFluxes[i, g] represents the flux in group g
             for pin i. Flux units are the standard n/cm^2/s. The "ARMI pin ordering" is used, which
             is counter-clockwise from 3 o'clock.
             """,
@@ -175,7 +175,7 @@ def _getNeutronicsBlockParams():
         pb.defParam(
             "pinMgFluxesAdj",
             units=units.UNITLESS,
-            description="should be a blank 3-D array, but re-defined later (ng x nPins x nAxialSegments)",
+            description="should be a blank 3-D array, but re-defined later (nPins x ng x nAxialSegments)",
             categories=[parameters.Category.pinQuantities],
             saveToDB=False,
             default=None,
@@ -184,7 +184,7 @@ def _getNeutronicsBlockParams():
         pb.defParam(
             "pinMgFluxesGamma",
             units=f"#/{units.CM}^2/{units.SECONDS}",
-            description="should be a blank 3-D array, but re-defined later (ng x nPins x nAxialSegments)",
+            description="should be a blank 3-D array, but re-defined later (nPins x ng x nAxialSegments)",
             categories=[parameters.Category.pinQuantities, parameters.Category.gamma],
             saveToDB=False,
             default=None,

armi/reactor/blocks.py

@@ -346,13 +346,10 @@ def setPinMgFluxes(self, fluxes, adjoint=False, gamma=False):
         """
         Store the pin-detailed multi-group neutron flux.
 
-        The [g][i] indexing is transposed to be a list of lists, one for each pin. This makes it
-        simple to do depletion for each pin, etc.
-
         Parameters
         ----------
-        fluxes : 2-D list of floats
-            The block-level pin multigroup fluxes. fluxes[g][i] represents the flux in group g for
+        fluxes : np.ndarray
+            The block-level pin multigroup fluxes. fluxes[i, g] represents the flux in group g for
             pin i. Flux units are the standard n/cm^2/s.
             The "ARMI pin ordering" is used, which is counter-clockwise from 3 o'clock.
         adjoint : bool, optional
@@ -362,28 +359,16 @@ def setPinMgFluxes(self, fluxes, adjoint=False, gamma=False):
 
         Outputs
         -------
-        self.p.pinMgFluxes : 2-D array of floats
-            The block-level pin multigroup fluxes. pinMgFluxes[g][i] represents the flux in group g
+        self.p.pinMgFluxes : np.ndarray
+            The block-level pin multigroup fluxes. pinMgFluxes[i, g] represents the flux in group g
             for pin i. Flux units are the standard n/cm^2/s.
             The "ARMI pin ordering" is used, which is counter-clockwise from 3 o'clock.
         """
-        pinFluxes = []
-
-        G, nPins = fluxes.shape
-
-        for pinNum in range(1, nPins + 1):
-            thisPinFlux = []
-
-            if self.hasFlags(Flags.FUEL):
-                pinLoc = self.p.pinLocation[pinNum - 1]
-            else:
-                pinLoc = pinNum
-
-            for g in range(G):
-                thisPinFlux.append(fluxes[g][pinLoc - 1])
-            pinFluxes.append(thisPinFlux)
+        if self.hasFlags(Flags.FUEL):
+            pinFluxes = fluxes[(np.array(self.p.pinLocation) - 1)]
+        else:
+            pinFluxes = fluxes[:]
 
-        pinFluxes = np.array(pinFluxes)
         if gamma:
             if adjoint:
                 raise ValueError("Adjoint gamma flux is currently unsupported.")

armi/reactor/tests/test_blocks.py

@@ -1700,13 +1700,29 @@ def test_pinMgFluxes(self):
 
         .. warning:: This will likely be pushed to the component level.
         """
-        fluxes = np.ones((33, 10))
+        fluxes = np.random.rand(10, 33)
+        p, g = np.random.randint(low=0, high=[10, 33])
+
+        # Test without pinLocation
+        self.block.pinLocation = None
         self.block.setPinMgFluxes(fluxes)
         self.block.setPinMgFluxes(fluxes * 2, adjoint=True)
         self.block.setPinMgFluxes(fluxes * 3, gamma=True)
-        self.assertEqual(self.block.p.pinMgFluxes[0][2], 1.0)
-        self.assertEqual(self.block.p.pinMgFluxesAdj[0][2], 2.0)
-        self.assertEqual(self.block.p.pinMgFluxesGamma[0][2], 3.0)
+        self.assertEqual(self.block.p.pinMgFluxes.shape, (10, 33))
+        self.assertEqual(self.block.p.pinMgFluxes[p, g], fluxes[p, g])
+        self.assertEqual(self.block.p.pinMgFluxesAdj.shape, (10, 33))
+        self.assertEqual(self.block.p.pinMgFluxesAdj[p, g], fluxes[p, g] * 2)
+        self.assertEqual(self.block.p.pinMgFluxesGamma.shape, (10, 33))
+        self.assertEqual(self.block.p.pinMgFluxesGamma[p, g], fluxes[p, g] * 3)
+
+        # Test with pinLocation
+        self.block.setType(self.block.getType(), Flags.FUEL)
+        self.block.p.pinLocation = np.random.choice(10, size=10, replace=False) + 1
+        self.block.setPinMgFluxes(fluxes)
+        self.assertEqual(self.block.p.pinMgFluxes.shape, (10, 33))
+        self.assertEqual(
+            self.block.p.pinMgFluxes[p, g], fluxes[self.block.p.pinLocation[p] - 1, g]
+        )
 
     def test_getComponentsInLinkedOrder(self):
         comps = self.block.getComponentsInLinkedOrder()

doc/release/0.4.rst

@@ -31,6 +31,7 @@ API Changes
 #. Allowing for unknown Flags when opening a DB. (`PR#1844 <https://github.com/terrapower/armi/pull/1835>`_)
 #. Removing ``assemblyLists.py`` and the ``AssemblyList`` class. (`PR#1891 <https://github.com/terrapower/armi/pull/1891>`_)
 #. Removing ``Assembly.rotatePins`` and ``Block.rotatePins``. Prefer ``Assembly.rotate`` and ``Block.rotate``. (`PR#1846 <https://github.com/terrapower/armi/1846`_)
+#. Transposing ``pinMgFluxes`` parameters so that leading dimension is pin index (`PR#1937 <https://github.com/terrapower/armi/pull/1937>`)
 #. TBD
 
 Bug Fixes