Add ATVR to vcache analyzer

ACMR is a good metric in general but the optimal ACMR number for a given
mesh depends on the triangle/vertex ratio - ACMR of 0.5 is impossible to
reach for certain meshes. In contrast, if we assume all vertices are
required by a given mesh, ATVR (average transform to vertex ratio) has
to be at least 1.0 (each vertex is transformed once), and represents the
amount of over-transformation due to vertex cache misses.

demo/main.cpp

@@ -139,7 +139,7 @@ void optimize(const Mesh& mesh, const char* name, void (*optf)(Mesh& mesh))
 
 	PostTransformCacheStatistics stats = analyzePostTransform(&copy.indices[0], copy.indices.size(), copy.vertices.size(), kCacheSize);
 
-	printf("%-10s: ACMR %f in %f msec\n", name, stats.acmr, double(end - start) / CLOCKS_PER_SEC * 1000);
+	printf("%-10s: ACMR %f ATVR %f in %f msec\n", name, stats.acmr, stats.atvr, double(end - start) / CLOCKS_PER_SEC * 1000);
 }
 
 int main(int argc, char** argv)

src/meshoptimizer.hpp

@@ -47,7 +47,8 @@ struct PostTransformCacheStatistics
 {
 	unsigned int hits, misses;
 	float hit_percent, miss_percent;
-	float acmr; // transformed vertices / triangle count
+	float acmr; // transformed vertices / triangle count; best case 0.5, worst case 3.0, optimum depends on topology
+	float atvr; // transformed vertices / vertex count; best case 1.0, worse case 6.0, optimum is 1.0 (each vertex is transformed once)
 };
 
 // Vertex transform cache analyzer

src/vcacheanalyzer.cpp

@@ -29,6 +29,7 @@ namespace
 		result.miss_percent = 100 * static_cast<float>(result.misses) / index_count;
 
 		result.acmr = static_cast<float>(result.misses) / (index_count / 3);
+		result.atvr = static_cast<float>(result.misses) / vertex_count;
 
 		return result;
 	}