move to Pythia8 random number generator

Generators/Pythia8_i/src/UserHooks/DecayToSUEP.cxx

@@ -115,7 +115,7 @@ namespace Pythia8{
 	particleFound=true;
 
 	//setup SUEP shower
-	static Suep_shower suep_shower(m_darkMesonMass(settingsPtr), m_darkTemperature(settingsPtr), m_mass(settingsPtr));
+	static Suep_shower suep_shower(m_darkMesonMass(settingsPtr), m_darkTemperature(settingsPtr), m_mass(settingsPtr), rndmPtr);
 
 #ifdef SUEP_DEBUG
 	std::cout << "[SUEP_DEBUG] " << "Particle (pdgId=" << m_pdgId(settingsPtr) << ", isFinal=True) found. Decaying to SUEP now." << std::endl;

Generators/Pythia8_i/src/UserHooks/suep_shower.cxx

@@ -10,10 +10,11 @@ using namespace std;
 using namespace Pythia8;
 
   // constructor
-  Suep_shower::Suep_shower(double mass, double temperature, double energy) {
+  Suep_shower::Suep_shower(double mass, double temperature, double energy, Pythia8::Rndm *rndm) {
     m = mass;
     Temp=temperature;
     Etot=energy;
+    rndmEngine = rndm;
     
     A=m/Temp;
     p_m=std::sqrt(2/(A*A)*(1+std::sqrt(1+A*A)));
@@ -56,8 +57,13 @@ using namespace Pythia8;
     double U(0.0), V(0.0), X(0.0), Y(0.0), E(0.0);
     int i=0;      
     while(i<100){
-      U = ((double) rand() / RAND_MAX);
-      V = ((double) rand() / RAND_MAX);
+      if (rndmEngine) {
+	U = rndmEngine->flat();
+	V = rndmEngine->flat();
+      } else {
+	U = ((double) rand() / RAND_MAX);
+	V = ((double) rand() / RAND_MAX);
+      }
         
       if(U < q_m){
 	Y=U/q_m;
@@ -85,8 +91,13 @@ using namespace Pythia8;
     p=X*(this->m); // X is the dimensionless momentum, p/m
     
     // now do the angles
-    phi = 2.0*M_PI*((double) rand() / RAND_MAX);
-    theta = acos(2.0*((double) rand() / RAND_MAX)-1.0);
+    if (rndmEngine) {
+      phi = 2.0*M_PI*(rndmEngine->flat());
+      theta = acos(2.0*rndmEngine->flat()-1.0);
+    } else {
+      phi = 2.0*M_PI*((double) rand() / RAND_MAX);
+      theta = acos(2.0*((double) rand() / RAND_MAX)-1.0);
+    }
     
     // compose the 4 vector
     en = std::sqrt(p*p+(this->m)*(this->m));

Generators/Pythia8_i/src/UserHooks/suep_shower.h

@@ -11,6 +11,7 @@
 #include <boost/math/tools/roots.hpp>
 #include <boost/bind.hpp>
 #include "Pythia8/PhaseSpace.h"
+#include "Pythia8/Basics.h"
 
 //** Auxiliary class for tolerance checks */
 class tolerance {
@@ -32,13 +33,21 @@ class Suep_shower
 { 
  public:
   
-  // Constructor
-  Suep_shower(double mass, double temperature, double energy);
+  /** Constructor.
+   * @param mass Mass of the dark meson
+   * @param temperature model parameter
+   * @param energy total energy of decaying system
+   * @param rndm random number generator, if any (if not provided will use the rand() function).
+   */
+  Suep_shower(double mass, double temperature, double energy, Pythia8::Rndm *rndm = 0);
   
   /** Generate a shower event, in the rest frame of the showe. */
   std::vector< Pythia8::Vec4 > generate_shower();
   
  protected: 
+
+  /** Random number generator, if not provided will use rand() */
+  Pythia8::Rndm *rndmEngine;
   
   /** Mass of the dark mesons to be generated in the shower */
   double m;