collapse the bins if the caller requests a monotone direction on a no…

…minal or multiclass target

shared/libebm/GenerateTermUpdate.cpp

@@ -949,7 +949,8 @@ EBM_API_BODY ErrorEbm EBM_CALLING_CONVENTION GenerateTermUpdate(void* rng,
       // are going to remain having 0 splits.
       pBoosterShell->GetInnerTermUpdate()->Reset();
 
-      if(IntEbm{0} == lastDimensionLeavesMax || (1 != cRealDimensions && MONOTONE_NONE != monotoneDirection)) {
+      if(IntEbm{0} == lastDimensionLeavesMax ||
+            ((1 != cRealDimensions || bNominal || 1 != cScores) && MONOTONE_NONE != monotoneDirection)) {
          // this is kind of hacky where if any one of a number of things occurs (like we have only 1 leaf)
          // we sum everything into a single bin. The alternative would be to always sum into the tensor bins
          // but then collapse them afterwards into a single bin, but that's more work.

shared/libebm/PartitionOneDimensionalBoosting.cpp

@@ -779,9 +779,13 @@ template<bool bHessian, size_t cCompilerScores> class PartitionOneDimensionalBoo
       EBM_ASSERT(2 <= cBins); // filter these out at the start where we can handle this case easily
       EBM_ASSERT(1 <= cSplitsMax); // filter these out at the start where we can handle this case easily
       EBM_ASSERT(nullptr != pTotalGain);
+      EBM_ASSERT(!bNominal || MONOTONE_NONE == monotoneDirection);
 
       BoosterCore* const pBoosterCore = pBoosterShell->GetBoosterCore();
       const size_t cScores = GET_COUNT_SCORES(cCompilerScores, pBoosterCore->GetCountScores());
+
+      EBM_ASSERT(1 == cScores || MONOTONE_NONE == monotoneDirection);
+
       const size_t cBytesPerBin = GetBinSize<FloatMain, UIntMain>(true, true, bHessian, cScores);
       auto* const pRootTreeNode = pBoosterShell->GetTreeNodesTemp<bHessian, GetArrayScores(cCompilerScores)>();
       pRootTreeNode->Init();