Rationalise RBC PRNGs

Author: rupertnash

Code/configuration/SimConfig.h

@@ -89,8 +89,11 @@ namespace hemelb::configuration
         PhysicalPosition origin_m;
     };
 
+    // Using std::minstd_rand with a 32 bit unsigned seed/state.
+    using PrngSeedType = std::uint32_t;
+
     struct CellInserterConfig {
-        std::int64_t seed;
+        PrngSeedType seed;
         std::string template_name;
         quantity_union<double, "s", "lattice"> offset;
         Angle theta_rad;

Code/redblood/CellControllerBuilder.cc

@@ -233,7 +233,7 @@ namespace hemelb::redblood {
             auto time = std::make_shared<LatticeTime>(timeStep - 1e0
                                                       + std::numeric_limits<LatticeTime>::epsilon() - offset);
 
-            std::default_random_engine randomGenerator(conf.seed);
+            std::minstd_rand randomGenerator(conf.seed);
             std::uniform_real_distribution<double> uniformDistribution(-1.0, 1.0);
 
             auto condition = [time, timeStep, dt, uniformDistribution, randomGenerator]() mutable

Code/redblood/RBCInserter.h

@@ -32,7 +32,7 @@ namespace hemelb::redblood
      */
     class RBCInserter
     {
-      public:
+    public:
         /**
          * Creates an RBC Inserter.
          *
@@ -106,12 +106,14 @@ namespace hemelb::redblood
     //! Red blood cell inserter that adds random rotation and translation to each cell
     class RBCInserterWithPerturbation : public RBCInserter
     {
-      public:
+    public:
+        using PRNG = std::minstd_rand;
+
         RBCInserterWithPerturbation(std::function<bool()> condition,
                                     std::unique_ptr<CellBase const> cell,
                                     util::Matrix3D const &initialRotation, Angle dtheta, Angle dphi,
                                     LatticePosition const& dx, LatticePosition const& dy,
-                                    std::default_random_engine::result_type randomGeneratorSeed = std::default_random_engine::default_seed) :
+                                    PRNG::result_type randomGeneratorSeed = PRNG::default_seed) :
             RBCInserter(condition, std::move(cell)), initialRotation(initialRotation),
                 dtheta(dtheta), dphi(dphi), dx(dx), dy(dy), randomGenerator(randomGeneratorSeed), uniformDistribution(-1.0,1.0)
         {
@@ -129,7 +131,7 @@ namespace hemelb::redblood
         //! Two vectors alongst which to move cell
         LatticePosition dx, dy;
 
-        std::default_random_engine randomGenerator;
+        PRNG randomGenerator;
         std::uniform_real_distribution<double> uniformDistribution;
     };