Added option to change random number seed based on cmfd_parallel branch.

docs/source/usersguide/input.rst

@@ -404,6 +404,14 @@ sub-elements and can be set to either "off" or "on".
 
   *Default*: on
 
+``seed`` Element
+----------------
+
+The ``seed`` element is used to set the seed used for the linear congruential
+pseudo-random number generator.
+
+  *Default*: 1
+
 ``source`` Element
 ------------------
 

src/global.F90

@@ -211,6 +211,9 @@ module global
   ! Message used in message/warning/fatal_error
   character(MAX_LINE_LEN) :: message
 
+  ! Random number seed
+  integer(8) :: seed = 1_8
+
   ! Problem type
   integer :: problem_type = PROB_CRITICALITY
 

src/initialize.F90

@@ -72,15 +72,15 @@ contains
        call header("INITIALIZATION", level=1)
     end if
 
-    ! Initialize random number generator
-    call initialize_prng()
-
     ! set up dictionaries
     call create_dictionaries()
 
     ! Read XML input files
     call read_input_xml()
 
+    ! Initialize random number generator
+    call initialize_prng()
+
     ! Set up universe structures
     call prepare_universes()
 

src/input_xml.F90

@@ -68,6 +68,7 @@ contains
     cross_sections_ = ""
     verbosity_ = 0
     energy_grid_ = "union"
+    seed_ = 0_8
 
     ! Parse settings.xml file
     call read_xml_file_settings_t(filename)
@@ -112,6 +113,9 @@ contains
        call fatal_error()
     end if
 
+    ! Copy random number seed if specified
+    if (seed_ > 0) seed = seed_
+
     ! Energy grid methods
     select case (energy_grid_)
     case ('nuclide')

src/random_lcg.F90

@@ -49,7 +49,9 @@ contains
 
   subroutine initialize_prng()
 
-    prn_seed0  = 1_8
+    use global, only: seed
+
+    prn_seed0  = seed
     prn_seed   = prn_seed
     prn_mult   = 2806196910506780709_8
     prn_add    = 1_8

src/xml-fortran/templates/settings_t.xml

@@ -32,6 +32,7 @@
   <variable name="energy_grid_" tag="energy_grid" type="word" length="7" />
   <variable name="entropy_" tag="entropy" type="entropy_xml" dimension="1" />
   <variable name="ptables_" tag="ptables" type="word" length="3" />
+  <variable name="seed_" tag="seed" type="integer" />
   <variable name="source_" tag="source" type="source_xml" />
   <variable name="survival_" tag="survival_biasing" type="word" length="3" />
   <variable name="verbosity_" tag="verbosity" type="integer" />