code cleanup

Author: breznak

src/examples/mnist/MNIST_SP.cpp

@@ -88,7 +88,7 @@ void setup() {
     /* synPermConnected */            0.5f, //no difference, let's leave at 0.5 in the middle
     /* minPctOverlapDutyCycles */     0.2f, //speed of re-learning?
     /* dutyCyclePeriod */             1402,
-    /* boostStrength */               7.0f, // Boosting does help, but entropy is high, on MNIST it does not matter, for learning with TM prefer boosting off (=0.0), or "neutral"=1.0
+    /* boostStrength */               7.0f, // Boosting does help, but entropy is high, on MNIST it does not matter, for learning with TM prefer boosting off (BOOSTING_DISABLED), or "neutral"=1.0
     /* seed */                        4u,
     /* spVerbosity */                 1u,
     /* wrapAround */                  true); // does not matter (helps slightly)

src/htm/algorithms/SpatialPooler.cpp

@@ -758,20 +758,20 @@ void applyBoosting_(const UInt i,
 		    const vector<Real>& actualDensity,
 		    const Real boost,
 	            vector<Real>& output) {
-
-  if(boost == SpatialPooler::BOOSTING_LOG) { //logarithmic boosting
+  if(boost == SpatialPooler::BOOSTING_DISABLED) output[i] = actualDensity[i]; //no change
+  else if(boost == SpatialPooler::BOOSTING_LOG) { //logarithmic boosting
     output[i] = log2(actualDensity[i]) / log2(targetDensity);
-  } else if(boost > 0) { //exponential boost
+  } else if(boost >= SpatialPooler::BOOSTING_EXP) { //exponential boost
     output[i] = exp((targetDensity - actualDensity[i]) * boost);
-  } //else: BOOSTING_DISABLED
+  } else NTA_THROW << "Invalid boost mode! " << boost; 
 }
 
 
 void SpatialPooler::updateBoostFactorsGlobal_() {
   Real targetDensity;
   if (numActiveColumnsPerInhArea_ > 0) {
     UInt inhibitionArea =
-        (UInt)(pow((Real)(2 * inhibitionRadius_ + 1), (Real)columnDimensions_.size()));
+        (UInt)(pow((Real)(2 * inhibitionRadius_ + 1), (Real)columnDimensions_.size())); //FIXME make this correct for nD with smaller dims: (28,28) vs (28,28,1) vs (28*28, 1)
     inhibitionArea = min(inhibitionArea, numColumns_);
     NTA_ASSERT(inhibitionArea > 0);
     targetDensity = ((Real)numActiveColumnsPerInhArea_) / inhibitionArea;
@@ -792,12 +792,12 @@ void SpatialPooler::updateBoostFactorsLocal_() {
     Real localActivityDensity = 0.0f;
 
     if (wrapAround_) {
-      for(auto neighbor: WrappingNeighborhood(i, inhibitionRadius_, columnDimensions_)) {
+      for(const auto neighbor: WrappingNeighborhood(i, inhibitionRadius_, columnDimensions_)) {
         localActivityDensity += activeDutyCycles_[neighbor];
         numNeighbors += 1;
       }
     } else {
-      for(auto neighbor: Neighborhood(i, inhibitionRadius_, columnDimensions_)) {
+      for(const auto neighbor: Neighborhood(i, inhibitionRadius_, columnDimensions_)) {
         localActivityDensity += activeDutyCycles_[neighbor];
         numNeighbors += 1;
       }

src/htm/algorithms/SpatialPooler.hpp

@@ -35,8 +35,6 @@ namespace htm {
 
 using namespace std;
 
-static const int DISABLED = -1; //value denoting a feature is disabled
-
 /**
  * CLA spatial pooler implementation in C++.
  *
@@ -63,19 +61,30 @@ static const int DISABLED = -1; //value denoting a feature is disabled
 class SpatialPooler : public Serializable
 {
 public:
+  static const constexpr Real DISABLED = -1.0f; //value denoting a feature is disabled
+  //boosting modes:
   static const constexpr Real BOOSTING_DISABLED = 0.0f;
-  static const constexpr Real BOOSTING_LOG      = -1234.0f;
+  static const constexpr Real BOOSTING_LOG      = -1.0f * htm::Epsilon; //negative value closest to 0, so it's possible to search <BOOSTING_LOG, (DISABLED=0.0),..10.0> in parameter optimization to try all 3 combinations of boosting. 
+  static const constexpr Real BOOSTING_EXP      = 1.0f * htm::Epsilon; //any value > BOOSTING_DISABLED enables the exponential boosting mode
 
   SpatialPooler();
-  SpatialPooler(const vector<UInt> inputDimensions, const vector<UInt> columnDimensions,
-                UInt potentialRadius = 16u, Real potentialPct = 0.5f,
-                bool globalInhibition = true, Real localAreaDensity = DISABLED,
+  SpatialPooler(const vector<UInt> inputDimensions, 
+		const vector<UInt> columnDimensions,
+                UInt potentialRadius = 16u, 
+		Real potentialPct = 0.5f,
+                bool globalInhibition = true, 
+		Real localAreaDensity = DISABLED,
                 Int numActiveColumnsPerInhArea = 10u,
-                UInt stimulusThreshold = 0u, Real synPermInactiveDec = 0.008f,
-                Real synPermActiveInc = 0.05f, Real synPermConnected = 0.1f,
+                UInt stimulusThreshold = 0u, 
+		Real synPermInactiveDec = 0.008f,
+                Real synPermActiveInc = 0.05f, 
+		Real synPermConnected = 0.1f,
                 Real minPctOverlapDutyCycles = 0.001f,
-                UInt dutyCyclePeriod = 1000u, Real boostStrength = 0.0f,
-                Int seed = 1, UInt spVerbosity = 0u, bool wrapAround = true);
+                UInt dutyCyclePeriod = 1000u, 
+		Real boostStrength = BOOSTING_DISABLED,
+                Int seed = 1, 
+		UInt spVerbosity = 0u, 
+		bool wrapAround = true);
 
   virtual ~SpatialPooler() {}
 
@@ -204,6 +213,9 @@ class SpatialPooler : public Serializable
 	This helps achieving the target sparsity of the output.
 	However, too much boosting may also lead to instability of SP outputs.
 
+	Notes:
+	- Log boosting does not require a parameter, but it is slower than exp.
+
 
   @param seed Seed for our random number generator. If seed is < 0
         a randomly generated seed is used. The behavior of the spatial

src/htm/types/Types.hpp

@@ -130,7 +130,7 @@ typedef std::size_t Size;
  *     numeric_limits<float>::epsilon()  == 1.19209e-7
  *     numeric_limits<double>::epsilon() == 2.22045e-16
  */
-static const htm::Real32 Epsilon = htm::Real(1e-6);
+static const constexpr htm::Real32 Epsilon = htm::Real(1e-6);
 
 /**
  * Represents a signed integer.