[dasher: 25/38] Fix uniformity in RoutingPPM, make sure each route gets at least 1!

[Patrick Welche <pwelche src gnome org>]

commit 099afd0ed2b3feacfa9f7172b0b1707530b4b851
Author: Alan Lawrence <acl33 inf phy cam ac uk>
Date:   Mon Dec 19 12:48:50 2011 +0000

    Fix uniformity in RoutingPPM, make sure each route gets at least 1!
    
    Otherwise some routes were disappearing after training.

 .../LanguageModelling/RoutingPPMLanguageModel.cpp  |   15 +++++++++------
 1 files changed, 9 insertions(+), 6 deletions(-)
---
diff --git a/Src/DasherCore/LanguageModelling/RoutingPPMLanguageModel.cpp b/Src/DasherCore/LanguageModelling/RoutingPPMLanguageModel.cpp
index 0737869..20ed83c 100644
--- a/Src/DasherCore/LanguageModelling/RoutingPPMLanguageModel.cpp
+++ b/Src/DasherCore/LanguageModelling/RoutingPPMLanguageModel.cpp
@@ -31,8 +31,8 @@ CRoutingPPMLanguageModel::CRoutingPPMLanguageModel(CSettingsUser *pCreator, cons
 void CRoutingPPMLanguageModel::GetProbs(Context context, std::vector<unsigned int> &probs, int norm, int iUniform) const {
   const CPPMContext *ppmcontext = (const CPPMContext *)(context);
 
-  const int iNumSymbols(m_pBaseSyms->size()); //i.e., the #routes - so loop from i=1 to <iNumSymbols
-  probs.resize(iNumSymbols);
+  const int iNumRoutes(m_pBaseSyms->size()); //i.e., the #routes - so loop from i=1 to <iNumSymbols
+  probs.resize(iNumRoutes);
   
   unsigned int iToSpend = norm;
   unsigned int iUniformLeft = iUniform;
@@ -40,9 +40,12 @@ void CRoutingPPMLanguageModel::GetProbs(Context context, std::vector<unsigned in
   // TODO: Sort out zero symbol case
   probs[0] = 0;
   
-  for(int i = 1; i < iNumSymbols; i++) {
-    probs[i] = iUniformLeft / (iNumSymbols - i);
-    iUniformLeft -= probs[i];
+  //Make sure each ROUTE gets at least one
+  for(int i = 1; i < iNumRoutes; i++) {
+    if (iUniformLeft >= iNumRoutes-i)
+      iUniformLeft -= probs[i] = iUniformLeft / (iNumRoutes-i);
+    else
+      probs[i]=1; //leave iUniformLeft
     iToSpend -= probs[i];
   }
   
@@ -109,7 +112,7 @@ void CRoutingPPMLanguageModel::GetProbs(Context context, std::vector<unsigned in
   //for each base, distribute any remaining probability mass
   // uniformly to all the routes to that base.
   for (int i=1; i<GetSize(); i++) {
-    if (!baseProbs[i]) continue; //=already distributed
+    if (!baseProbs[i]) continue; //none for that base (routes already have >=1), or already distributed
     
     //ok, so there's some probability mass assigned to the base symbol,
     // which we haven't assigned to any route