Merge branch 'develop' into lost_particle_plotting01

Conflicts:
	man/man1/openmc.1
	src/output.F90
	src/source.F90

docs/source/usersguide/input.rst

@@ -381,6 +381,14 @@ survival biasing, otherwise known as implicit capture or absorption.
 
 .. _trace:
 
+``<threads>`` Element
+---------------------
+
+The ``<threads>`` element indicates the number of OpenMP threads to be used for
+a simulation. It has no attributes and accepts a positive integer value.
+
+  *Default*: None (Determined by environment variable :envvar:`OMP_NUM_THREADS`)
+
 ``<trace>`` Element
 -------------------
 

docs/source/usersguide/install.rst

@@ -141,6 +141,10 @@ MPI
   Enables parallel runs using the Message Passing Interface. The MPI_DIR
   variable should be set to the base directory of the MPI implementation.
 
+OPENMP
+  Enables shared-memory parallelism using the OpenMP API. The Fortran compiler
+  being used must support OpenMP.
+
 HDF5
   Enables HDF5 output in addition to normal screen and text file output. The
   HDF5_DIR variable should be set to the base directory of the HDF5
@@ -326,6 +330,20 @@ Alternatively, you could run from any directory:
 Note that in the latter case, any output files will be placed in the present
 working directory which may be different from ``/home/username/somemodel``.
 
+Command-Line Flags
+------------------
+
+OpenMC accepts the following command line flags:
+
+-g, --geometry-debug   Run in geometry debugging mode, where cell overlaps are
+                       checked for after each move of a particle
+-n, --particles N      Use *N* particles per generation or batch
+-p, --plot             Run in plotting mode
+-r, --restart file     Restart a previous run from a state point or a particle
+                       restart file
+-s, --threads N        Run with *N* OpenMP threads
+-v, --version          Show version information
+
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