diff --git a/Code/debug/Debugger.cc b/Code/debug/Debugger.cc
index 66b250f02..a7925e9ff 100644
--- a/Code/debug/Debugger.cc
+++ b/Code/debug/Debugger.cc
@@ -15,7 +15,7 @@ namespace hemelb
   namespace debug
   {
 
-    Debugger* Debugger::Init(const char * const executable)
+    Debugger* Debugger::Init(const char * const executable, const net::MpiCommunicator& comm)
     {
       /* Static member function that implements the singleton pattern.
        * Use the namespace function PlatformDebuggerFactory to
@@ -24,7 +24,7 @@ namespace hemelb
        */
       if (Debugger::singleton == NULL)
       {
-        Debugger::singleton = PlatformDebuggerFactory(executable);
+        Debugger::singleton = PlatformDebuggerFactory(executable, comm);
       }
       Debugger::singleton->Attach();
       return Debugger::singleton;
@@ -39,10 +39,9 @@ namespace hemelb
     // Init static members
     Debugger* Debugger::singleton = NULL;
 
-    Debugger::Debugger(const char* const executable)
+    Debugger::Debugger(const char* const executable, const net::MpiCommunicator& comm) :
+      mExecutable(executable), mCommunicator(comm)
     {
-      // Ctor
-      mExecutable = std::string(executable);
     }
 
     // Dtor
diff --git a/Code/debug/Debugger.h b/Code/debug/Debugger.h
index 1c19ffe02..fe3c50f17 100644
--- a/Code/debug/Debugger.h
+++ b/Code/debug/Debugger.h
@@ -11,6 +11,7 @@
 #define HEMELB_DEBUG_DEBUGGER_H
 
 #include <string>
+#include "net/MpiCommunicator.h"
 
 namespace hemelb
 {
@@ -24,26 +25,26 @@ namespace hemelb
          */
       public:
         // the singleton pattern
-        static Debugger* Init(const char *const);
+        static Debugger* Init(const char *const, const net::MpiCommunicator& comm);
         static Debugger* Get(void);
 
         virtual void BreakHere(void) = 0;
         virtual void Print(const char* iFormat, ...) = 0;
 
       protected:
-        Debugger(const char* const executable);
+        Debugger(const char* const executable, const net::MpiCommunicator& comm);
         virtual ~Debugger();
 
         virtual void Attach() = 0;
 
         std::string mExecutable;
-
+        const net::MpiCommunicator mCommunicator;
         // Singleton pattern
         static Debugger* singleton;
 
     };
 
-    Debugger* PlatformDebuggerFactory(const char* const executable);
+    Debugger* PlatformDebuggerFactory(const char* const executable, const net::MpiCommunicator& comm);
 
   }
 }
diff --git a/Code/debug/OSX/OsxDebugger.cc b/Code/debug/OSX/OsxDebugger.cc
index b6fb5eb8f..cf25b6d47 100644
--- a/Code/debug/OSX/OsxDebugger.cc
+++ b/Code/debug/OSX/OsxDebugger.cc
@@ -15,29 +15,36 @@ namespace hemelb
 {
   namespace debug
   {
-    OsxDebugger::OsxDebugger(const char* const executable) : ActiveDebugger(executable) {}
-    
-    const std::string OsxDebugger::GetPlatformInterpreter(void) const {
+    OsxDebugger::OsxDebugger(const char* const executable, const net::MpiCommunicator& comm) :
+      ActiveDebugger(executable, comm)
+    {
+    }
+
+    const std::string OsxDebugger::GetPlatformInterpreter(void) const
+    {
       return std::string("osascript");
     }
-    
-    const std::string OsxDebugger::GetPlatformScript(void) const {
-      std::string include (__FILE__);
+
+    const std::string OsxDebugger::GetPlatformScript(void) const
+    {
+      std::string include(__FILE__);
       std::string debugOsxDir = include.substr(0, include.rfind('/'));
-      
+
       return debugOsxDir + "/MPIdebug.scpt";
     }
-    
-    const std::string OsxDebugger::GetPlatformGdbScript(void) const {
-      std::string include (__FILE__);
+
+    const std::string OsxDebugger::GetPlatformGdbScript(void) const
+    {
+      std::string include(__FILE__);
       std::string debugOsxDir = include.substr(0, include.rfind('/'));
-      
+
       return debugOsxDir + "/resume.gdb";
     }
 
-    Debugger* PlatformDebuggerFactory(const char * const executable) {
-      return new OsxDebugger(executable);
+    Debugger* PlatformDebuggerFactory(const char * const executable, const net::MpiCommunicator& comm)
+    {
+      return new OsxDebugger(executable, comm);
     }
- 
+
   } // namespace debug
 } // namespace hemelb
diff --git a/Code/debug/OSX/OsxDebugger.h b/Code/debug/OSX/OsxDebugger.h
index 13878b5a7..e0df27031 100644
--- a/Code/debug/OSX/OsxDebugger.h
+++ b/Code/debug/OSX/OsxDebugger.h
@@ -25,14 +25,14 @@ namespace hemelb
       const std::string GetPlatformGdbScript(void) const;
       
       // C'tor...
-      OsxDebugger(const char* const executable);
+      OsxDebugger(const char* const executable, const net::MpiCommunicator& comm);
       // ... which the factory function needs to be able to get at.
-      friend Debugger* PlatformDebuggerFactory(const char* const executable);
+      friend Debugger* PlatformDebuggerFactory(const char* const executable, const net::MpiCommunicator& comm);
       
     };
     
     // Factory. Don't be calling this.
-    Debugger* PlatformDebuggerFactory(const char* const executable);
+    Debugger* PlatformDebuggerFactory(const char* const executable, const net::MpiCommunicator& comm);
   }
 }
 
diff --git a/Code/debug/common/ActiveDebugger.cc b/Code/debug/common/ActiveDebugger.cc
index 56ec89231..2880fe507 100644
--- a/Code/debug/common/ActiveDebugger.cc
+++ b/Code/debug/common/ActiveDebugger.cc
@@ -31,8 +31,8 @@ namespace hemelb
   namespace debug
   {
 
-    ActiveDebugger::ActiveDebugger(const char* const executable) :
-      Debugger(executable), mAmAttached(false), mPIds(NULL)
+    ActiveDebugger::ActiveDebugger(const char* const executable, const net::MpiCommunicator& comm) :
+      Debugger(executable, comm), mAmAttached(false), mPIds(NULL)
     {
     }
 
@@ -67,27 +67,15 @@ namespace hemelb
         return;
 
       volatile int amWaiting = 1;
-      int rank;
-      MPI_Comm_rank(MPI_COMM_WORLD, &rank);
-      int nProcs;
-      MPI_Comm_size(MPI_COMM_WORLD, &nProcs);
-      mPIds = new VoI(nProcs);
-      int pId = getpid();
-      pid_t childPid = 0;
-
-      MPI_Gather((void*) &pId,
-                 1,
-                 net::MpiDataType(pId),
-                 (void*) & (mPIds->front()),
-                 1,
-                 net::MpiDataType(mPIds->front()),
-                 0,
-                 MPI_COMM_WORLD);
-
-      if (rank == 0)
+
+      int childPid = -1;
+      // To rank 0
+      GatherProcessIds();
+
+      if (mCommunicator.Rank() == 0)
       {
         childPid = fork();
-
+        // Fork gives the PID of the child to the parent and zero to the child
         if (childPid == 0)
         {
           // This function won't return.
@@ -99,7 +87,7 @@ namespace hemelb
       while (amWaiting)
         sleep(5);
 
-      if (rank == 0)
+      if (mCommunicator.Rank() == 0)
       {
         // Reap the spawner
         int deadPid = waitpid(childPid, NULL, 0);
@@ -110,28 +98,22 @@ namespace hemelb
 
     void ActiveDebugger::GatherProcessIds()
     {
-      if (mAmAttached)
-      {
-        // Return a vector of the process ids
-        int rank;
-        MPI_Comm_rank(MPI_COMM_WORLD, &rank);
-        int nProcs;
-        MPI_Comm_size(MPI_COMM_WORLD, &nProcs);
-
-        mPIds = new VoI(nProcs);
+      int rank = mCommunicator.Rank();
+      int nProcs = mCommunicator.Size();
 
-        int pId = getpid();
+      mPIds = new VoI(nProcs);
 
-        MPI_Gather((void*) &pId,
-                   1,
-                   net::MpiDataType(pId),
-                   (void*) & (mPIds->front()),
-                   1,
-                   net::MpiDataType(mPIds->front()),
-                   0,
-                   MPI_COMM_WORLD);
+      int pId = getpid();
 
-      }
+      HEMELB_MPI_CALL(MPI_Gather,
+          ((void*) &pId,
+              1,
+              net::MpiDataType(pId),
+              (void*) & (mPIds->front()),
+              1,
+              net::MpiDataType(mPIds->front()),
+              0,
+              mCommunicator));
     }
 
     void ActiveDebugger::SpawnDebuggers(void)
diff --git a/Code/debug/common/ActiveDebugger.h b/Code/debug/common/ActiveDebugger.h
index 4a3aa2a51..b3aa74286 100644
--- a/Code/debug/common/ActiveDebugger.h
+++ b/Code/debug/common/ActiveDebugger.h
@@ -36,7 +36,7 @@ namespace hemelb
         typedef std::vector<std::string> VoS;// Vector of Strings
 
         // C'tor
-        ActiveDebugger(const char* const executable);
+        ActiveDebugger(const char* const executable, const net::MpiCommunicator& comm);
 
         bool mAmAttached;// Indicate attachment state
         VoI* mPIds;// vector of process IDs
diff --git a/Code/debug/linux/LinuxDebugger.cc b/Code/debug/linux/LinuxDebugger.cc
index 46f642ee1..99d9110a6 100644
--- a/Code/debug/linux/LinuxDebugger.cc
+++ b/Code/debug/linux/LinuxDebugger.cc
@@ -15,30 +15,30 @@ namespace hemelb
 {
   namespace debug
   {
-    LinuxDebugger::LinuxDebugger(const char* const executable) :
-      ActiveDebugger(executable) {}
-    
+    LinuxDebugger::LinuxDebugger(const char* const executable, const net::MpiCommunicator& comm) :
+      ActiveDebugger(executable, comm) {}
+
     const std::string LinuxDebugger::GetPlatformInterpreter(void) const {
       return std::string("bash");
     }
-    
+
     const std::string LinuxDebugger::GetPlatformScript(void) const {
       std::string include (__FILE__);
       std::string debugLinuxDir = include.substr(0, include.rfind('/'));
-      
+
       return debugLinuxDir + "/launchGdbs.sh";
     }
-    
+
     const std::string LinuxDebugger::GetPlatformGdbScript(void) const {
       std::string include (__FILE__);
       std::string debugLinuxDir = include.substr(0, include.rfind('/'));
-      
+
       return debugLinuxDir + "/resume.gdb";
     }
-    
-    Debugger* PlatformDebuggerFactory(const char * const executable) {
-      return new LinuxDebugger(executable);
+
+    Debugger* PlatformDebuggerFactory(const char * const executable, const net::MpiCommunicator& comm) {
+      return new LinuxDebugger(executable, comm);
     }
- 
+
   } // namespace debug
 } // namespace hemelb
diff --git a/Code/debug/linux/LinuxDebugger.h b/Code/debug/linux/LinuxDebugger.h
index f31d0e368..c8a011f2c 100644
--- a/Code/debug/linux/LinuxDebugger.h
+++ b/Code/debug/linux/LinuxDebugger.h
@@ -25,14 +25,14 @@ namespace hemelb
       const std::string GetPlatformGdbScript(void) const;
       
       // C'tor...
-      LinuxDebugger(const char* const executable);
+      LinuxDebugger(const char* const executable, const net::MpiCommunicator& comm);
       // ... which the factory function needs to be able to get at.
-      friend Debugger* PlatformDebuggerFactory(const char* const executable);
+      friend Debugger* PlatformDebuggerFactory(const char* const executable, const net::MpiCommunicator& comm);
       
     };
     
     // Factory. Don't be calling this.
-    Debugger* PlatformDebuggerFactory(const char* const executable);
+    Debugger* PlatformDebuggerFactory(const char* const executable, const net::MpiCommunicator& comm);
   }
 }
 
diff --git a/Code/debug/none/NullDebugger.cc b/Code/debug/none/NullDebugger.cc
index 17ef11f55..b7e894880 100644
--- a/Code/debug/none/NullDebugger.cc
+++ b/Code/debug/none/NullDebugger.cc
@@ -25,14 +25,14 @@ namespace hemelb
     {
     }
 
-    NullDebugger::NullDebugger(const char* const executable) :
-      Debugger(executable)
+    NullDebugger::NullDebugger(const char* const executable, const net::MpiCommunicator& comm) :
+      Debugger(executable, comm)
     {
     }
 
-    Debugger* PlatformDebuggerFactory(const char * const executable)
+    Debugger* PlatformDebuggerFactory(const char * const executable, const net::MpiCommunicator& comm)
     {
-      return new NullDebugger(executable);
+      return new NullDebugger(executable, comm);
     }
   }
 }
diff --git a/Code/debug/none/NullDebugger.h b/Code/debug/none/NullDebugger.h
index b03f697d1..691db31b2 100644
--- a/Code/debug/none/NullDebugger.h
+++ b/Code/debug/none/NullDebugger.h
@@ -24,11 +24,11 @@ namespace hemelb
 
       protected:
         void Attach(void);
-        NullDebugger(const char* const executable);
-        friend Debugger* PlatformDebuggerFactory(const char* const executable);
+        NullDebugger(const char* const executable, const net::MpiCommunicator& comm);
+        friend Debugger* PlatformDebuggerFactory(const char* const executable, const net::MpiCommunicator& comm);
     };
 
-    Debugger* PlatformDebuggerFactory(const char* const executable);
+    Debugger* PlatformDebuggerFactory(const char* const executable, const net::MpiCommunicator& comm);
   }
 }
 
diff --git a/Code/main.cc b/Code/main.cc
index 9907768aa..369da220f 100644
--- a/Code/main.cc
+++ b/Code/main.cc
@@ -23,10 +23,10 @@ int main(int argc, char *argv[])
   hemelb::log::Logger::Init();
   try
   {
+    hemelb::net::MpiCommunicator hemelbCommunicator = hemelb::net::MpiCommunicator::World();
     // Start the debugger (no-op if HEMELB_USE_DEBUGGER is OFF)
-    hemelb::debug::Debugger::Init(argv[0]);
+    hemelb::debug::Debugger::Init(argv[0], hemelbCommunicator);
 
-    hemelb::net::MpiCommunicator hemelbCommunicator = hemelb::net::MpiCommunicator::World();
     hemelb::net::NetworkTopology::Instance()->Init(hemelbCommunicator);
     try
     {
diff --git a/Code/unittests/main.cc b/Code/unittests/main.cc
index fdb9c8b93..082f1aaf1 100644
--- a/Code/unittests/main.cc
+++ b/Code/unittests/main.cc
@@ -37,6 +37,8 @@ int main(int argc, char **argv)
   hemelb::log::Logger::Init();
 
   hemelb::net::MpiCommunicator testCommunicator = hemelb::net::MpiCommunicator::World();
+  hemelb::debug::Debugger::Init(argv[0], testCommunicator);
+
   hemelb::net::NetworkTopology::Instance()->Init(testCommunicator);
 
   std::ostream * reportto=&std::cerr;