SP add check for too low sparsity x numColumns combination

when localAreaDensity, aka sparsity is set, check with column sizes
that produced active output columns could be > 0

Author: breznak

src/htm/algorithms/SpatialPooler.cpp

@@ -135,8 +135,10 @@ void SpatialPooler::setGlobalInhibition(bool globalInhibition) {
 
 Real SpatialPooler::getLocalAreaDensity() const { return localAreaDensity_; }
 
-void SpatialPooler::setLocalAreaDensity(Real localAreaDensity) {
+void SpatialPooler::setLocalAreaDensity(const Real localAreaDensity) {
   NTA_CHECK(localAreaDensity > 0.0f && localAreaDensity <= 1.0f);
+  NTA_CHECK(static_cast<UInt>(localAreaDensity * getNumColumns()) > 0) 
+	  << "Too small density or sp.getNumColumns() -> would have zero active output columns.";
   localAreaDensity_ = localAreaDensity;
 }
 
@@ -391,7 +393,7 @@ void SpatialPooler::initialize(
   NTA_CHECK(inputDimensions_.size() == columnDimensions_.size()); 
 
   NTA_CHECK(localAreaDensity > 0 && localAreaDensity <= MAX_LOCALAREADENSITY);
-  localAreaDensity_ = localAreaDensity;
+  setLocalAreaDensity(localAreaDensity); 
 
   rng_ = Random(seed);
 

src/test/unit/engine/CppRegionTest.cpp

@@ -112,7 +112,7 @@ TEST(CppRegionTest, testCppLinkingSDR) {
   Network net;
 
   std::shared_ptr<Region> region1 = net.addRegion("region1", "ScalarSensor", "{dim: [6,1], n: 6, w: 2}");
-  std::shared_ptr<Region> region2 = net.addRegion("region2", "SPRegion", "{dim: [2,3]}");
+  std::shared_ptr<Region> region2 = net.addRegion("region2", "SPRegion", "{dim: [20,3]}");
 
   net.link("region1", "region2"); 
 
@@ -130,7 +130,7 @@ TEST(CppRegionTest, testCppLinkingSDR) {
   const Array r1OutputArray = region1->getOutputData("encoded");
   VERBOSE << r1OutputArray << "\n";
   std::vector<Byte> expected = {0, 0, 0, 0, 1, 1};
-  EXPECT_TRUE(r1OutputArray == expected);
+  EXPECT_EQ(r1OutputArray, expected);
 
   region2->prepareInputs();
   region2->compute();
@@ -139,22 +139,24 @@ TEST(CppRegionTest, testCppLinkingSDR) {
   const Array r2InputArray = region2->getInputData("bottomUpIn");
   VERBOSE << r2InputArray << "\n";
   EXPECT_EQ(r2InputArray.getType(), NTA_BasicType_SDR);
-  EXPECT_TRUE(r2InputArray == expected);
+  EXPECT_EQ(r2InputArray,  expected);
 
   VERBOSE << "Region 2 input after first iteration:" << std::endl;
   const Dimensions r2dims = region2->getOutput("bottomUpOut")->getDimensions();
   EXPECT_EQ(r2dims.size(), 2u) << " actual dims: " << r2dims.toString();
-  EXPECT_EQ(r2dims[0], 2u) << " actual dims: " << r2dims.toString();
+  EXPECT_EQ(r2dims[0], 20u) << " actual dims: " << r2dims.toString(); //match dims of SPRegion constructed above
   EXPECT_EQ(r2dims[1], 3u) << " actual dims: " << r2dims.toString();
 
   const Array r2OutputArray = region2->getOutputData("bottomUpOut");
   EXPECT_EQ(r2OutputArray.getType(), NTA_BasicType_SDR);
   EXPECT_EQ(r2OutputArray.getSDR().dimensions, r2dims)
       << "Expected dimensions on the output to match dimensions on the buffer.";
   VERBOSE << r2OutputArray << "\n";
-  std::vector<Byte> expected_output = {1, 0, 1, 0, 1, 0};
-  EXPECT_TRUE(r2OutputArray ==  expected_output) << "expected " << r2OutputArray;
-
+  SDR exp({20u, 3u});
+  exp.setSparse(SDR_sparse_t{
+    4, 21, 32, 46
+  });
+  EXPECT_EQ(r2OutputArray, exp.getDense()) << "got " << r2OutputArray;
 }