From a64255bdc8d71e2d6118e5e2b55f22a155bb75b4 Mon Sep 17 00:00:00 2001
From: Adam Nelson <nelsonag@umich.edu>
Date: Tue, 25 Aug 2015 20:03:19 -0400
Subject: [PATCH] Cleaned up automatic binning code for mu filters and updated
 documentation/rng files

---
 docs/source/usersguide/input.rst | 15 +++++++++++++++
 src/input_xml.F90                |  9 +++++----
 src/relaxng/tallies.rnc          |  6 +++---
 src/relaxng/tallies.rng          |  2 ++
 src/tally.F90                    |  1 +
 5 files changed, 26 insertions(+), 7 deletions(-)

diff --git a/docs/source/usersguide/input.rst b/docs/source/usersguide/input.rst
index 93e8236ec1..6e244bc9b4 100644
--- a/docs/source/usersguide/input.rst
+++ b/docs/source/usersguide/input.rst
@@ -1251,6 +1251,21 @@ The ``<tally>`` element accepts the following sub-elements:
           two post-collision energy bins will be created, one with energies
           between 0 and 1 MeV and the other with energies between 1 and 20 MeV.
 
+        :mu:
+          A monotonically increasing list of bounding **post-collision**
+          cosines of the change in a particle's angle (i.e., :math:`\mu`),
+          which represents a portion of the possible values of :math:'\[-1,1\]'.
+          For example, spanning all of :math:'\[-1,1\]' with five equi-width
+          bins can be specified as:
+          ``<filter type="mu" bins="-1.0 -0.6 -0.2 0.2 0.6 1.0" />``
+
+          Alternatively, if only one value is provided as a bin, OpenMC will
+          interpret this to mean the complete range of :math:'\[-1,1\]' should
+          be automatically subdivided in to the provided value for the bin.
+          That is, the above example of five equi-width bins spanning
+          :math:'\[-1,1\]' can be instead written as:
+          ``<filter type="mu" bins="5" />``.
+
         :mesh:
           The ``id`` of a structured mesh to be tallied over.
 
diff --git a/src/input_xml.F90 b/src/input_xml.F90
index 22f991ab9e..b1cabb4cbb 100644
--- a/src/input_xml.F90
+++ b/src/input_xml.F90
@@ -2508,13 +2508,14 @@ contains
             if (n_words == 1) then
               Nmu = abs(int(t % filters(j) % real_bins(1)))
               if (Nmu > 1) then
-                t % filters(j) % n_bins = Nmu - 1
-                dmu = TWO / (real(Nmu,8) - ONE)
+                t % filters(j) % n_bins = Nmu
+                dmu = TWO / (real(Nmu,8))
                 deallocate(t % filters(j) % real_bins)
-                allocate(t % filters(j) % real_bins(Nmu))
-                do imu = 1, Nmu
+                allocate(t % filters(j) % real_bins(Nmu + 1))
+                do imu = 1, Nmu + 1
                   t % filters(j) % real_bins(imu) = -ONE + (imu - 1) * dmu
                 end do
+                t % filters(j) % real_bins(Nmu + 1) = ONE
               else
                 call fatal_error("Must have more than one bin for mu filter &
                      & on tally " // trim(to_str(t % id)) // ".")
diff --git a/src/relaxng/tallies.rnc b/src/relaxng/tallies.rnc
index c2e0860b8e..d3e5e87e83 100644
--- a/src/relaxng/tallies.rnc
+++ b/src/relaxng/tallies.rnc
@@ -23,16 +23,16 @@ element tallies {
       attribute estimator { ( "analog" | "tracklength" ) })? &
     element filter {
       (element type { ( "cell" | "cellborn" | "material" | "universe" |
-        "surface" | "distribcell" | "mesh" | "energy" | "energyout" ) } |
+        "surface" | "distribcell" | "mesh" | "energy" | "energyout" | "mu") } |
        attribute type { ( "cell" | "cellborn" | "material" | "universe" |
-        "surface" | "distribcell" | "mesh" | "energy" | "energyout" ) }) &
+        "surface" | "distribcell" | "mesh" | "energy" | "energyout" | "mu") }) &
       (element bins { list { xsd:double+ } } |
         attribute bins { list { xsd:double+ } })
     }* &
     element nuclides {
       list { xsd:string { maxLength = "12" }+ }
     }? &
-    element scores { 
+    element scores {
       list { xsd:string { maxLength = "20" }+ }
     } &
     element trigger {
diff --git a/src/relaxng/tallies.rng b/src/relaxng/tallies.rng
index 9ea941feab..ce0d2d1bcd 100644
--- a/src/relaxng/tallies.rng
+++ b/src/relaxng/tallies.rng
@@ -151,6 +151,7 @@
                       <value>mesh</value>
                       <value>energy</value>
                       <value>energyout</value>
+                      <value>mu</value>
                     </choice>
                   </element>
                   <attribute name="type">
@@ -164,6 +165,7 @@
                       <value>mesh</value>
                       <value>energy</value>
                       <value>energyout</value>
+                      <value>mu</value>
                     </choice>
                   </attribute>
                 </choice>
diff --git a/src/tally.F90 b/src/tally.F90
index d3fce52905..fc05145db4 100644
--- a/src/tally.F90
+++ b/src/tally.F90
@@ -1247,6 +1247,7 @@ contains
       case (FILTER_MU)
         ! determine mu bin
         n = t % filters(i) % n_bins
+
         ! search to find incoming energy bin
         matching_bins(i) = binary_search(t % filters(i) % real_bins, &
              n + 1, p % mu)