Lazy Vietoris-Rips which is sorted by construction. Worth writing up???

appliedtopology · May 6, 2024 · 4e5161b · 4e5161b
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diff --git a/src/main/scala/org/appliedtopology/tda4j/VietorisRips.scala b/src/main/scala/org/appliedtopology/tda4j/VietorisRips.scala
@@ -349,7 +349,8 @@ object LazyStratifiedVietorisRips {
   def apply[VertexT: Ordering](
     metricSpace: FiniteMetricSpace[VertexT],
     maxFiltrationValue: Double,
-    maxDimension: Int = 2) : Array[LazyList[AbstractSimplex[VertexT]]] =
+    maxDimension: Int = 2
+  ): Array[LazyList[AbstractSimplex[VertexT]]] =
     this(metricSpace, Some(maxFiltrationValue), maxDimension)
 
   def apply[VertexT: Ordering](
@@ -360,6 +361,9 @@ object LazyStratifiedVietorisRips {
 
     val filtrationValue = FiniteMetricSpace.MaximumDistanceFiltrationValue[VertexT](metricSpace)
 
+    inline def maxSize: Int = maxDimension + 1
+    val maxFVal = maxFiltrationValue.getOrElse(metricSpace.minimumEnclosingRadius)
+
     val lazyLists: Array[LazyList[AbstractSimplex[VertexT]]] = Array.ofDim(maxDimension + 1)
     lazyLists(0) = LazyList.from(metricSpace.elements.map(AbstractSimplex(_)))
     (1 to maxDimension).foreach(lazyLists(_) = LazyList.empty)
@@ -368,6 +372,9 @@ object LazyStratifiedVietorisRips {
       metricSpace.elements.toList
         .combinations(2)
         .toVector
+        .filter { xys =>
+          val List(x,y) = xys; metricSpace.distance(x,y) <= maxFVal
+        }
         .sortBy { xys =>
           val List(x, y) = xys; metricSpace.distance(x, y)
         }
@@ -393,8 +400,7 @@ object LazyStratifiedVietorisRips {
     )
     @tailrec def oneStep(foldState: FoldState): Array[LazyList[AbstractSimplex[VertexT]]] =
       if (foldState.taskStack.isEmpty) foldState.outputLists
-      else if (foldState.taskStack.head._1.size > maxDimension)
-        oneStep(foldState.copy(taskStack = foldState.taskStack.tail))
+      else if (foldState.taskStack.head._1.size > maxSize) oneStep(foldState.copy(taskStack = foldState.taskStack.tail))
       else {
         val (simplex, edge) = foldState.taskStack.head
         val List(src, tgt) = edge.toList.sorted // ensure src < tgt
@@ -431,3 +437,14 @@ object LazyStratifiedVietorisRips {
     oneStep(startState)
   }
 }
+
+class LazyStratifiedCliqueFinder[VertexT: Ordering]() extends CliqueFinder[VertexT] {
+  override val className: String = "LazyStratifiedCliqueFinder"
+  def apply(
+    metricSpace: FiniteMetricSpace[VertexT],
+    maxFiltrationValue: Double = Double.PositiveInfinity,
+    maxDimension: Int = 2
+  ): Seq[AbstractSimplex[VertexT]] =
+    LazyStratifiedVietorisRips(metricSpace, maxFiltrationValue, maxDimension)
+      .foldRight(LazyList[AbstractSimplex[VertexT]]())((lz, sq) => sq #::: lz)
+}
diff --git a/src/test/scala/org/appliedtopology/tda4j/ProfilingSpec.scala b/src/test/scala/org/appliedtopology/tda4j/ProfilingSpec.scala
@@ -11,7 +11,7 @@ import collection.immutable.BitSet
 class ProfilingSpec(args: Arguments) extends mutable.Specification {
   """This is a profiling script to measure performance of different implementations.""" >> {
     val bitlength: Int = args.commandLine.intOr("bitlength", 3)
-    val maxFVal: Double = args.commandLine.doubleOr("maxFVal", 7.0)
+    val maxFVal: Double = args.commandLine.doubleOr("maxFVal", 4.0)
     val maxDim: Int = args.commandLine.intOr("maxDim", 7)
 
     val symmetry: HyperCubeSymmetry = HyperCubeSymmetry(bitlength)
@@ -110,5 +110,17 @@ class ProfilingSpec(args: Arguments) extends mutable.Specification {
       symmetry_gen.representatives.size === symmetry_gen.representatives.size
     }
     section("ripser-gens")
+
+    section("lazy-stratified")
+    "Lazy Vietoris-Rips sorted by construction" >> {
+      val zi: HyperCubeProfiling =
+        HyperCubeProfiling(
+          LazyStratifiedCliqueFinder[Int](),
+          symmetry,
+          bitlength,
+          "LS"
+        )
+    }
+    section("lazy-stratified")
   }
 }