Specialise filtering for Ref arrays in Sets and Maps

Author: mikera

convex-core/src/main/java/convex/core/data/MapTree.java

@@ -102,17 +102,19 @@ public static <K extends ACell, V extends ACell> MapTree<K, V> create(MapEntry<K
 	 */
 	private static <K extends ACell, V extends ACell> AHashMap<K, V> createFull(Ref<AHashMap<K, V>>[] children, int shift, long count) {
 		if (children.length != FANOUT) throw new IllegalArgumentException("16 children required!");
-		Ref<AHashMap<K, V>>[] newChildren = Utils.filterArray(children, a -> {
-			if (a == null) return false;
-			AMap<K, V> m = a.getValue();
-			return ((m != null) && !m.isEmpty());
-		});
-
-		if (children != newChildren) {
-			return create(newChildren, shift, Utils.computeMask(children, newChildren), count);
-		} else {
-			return create(children, shift, (short) 0xFFFF, count);
+		int mask=0;
+		for (int i=0; i<FANOUT; i++) {
+			Ref<AHashMap<K, V>> ch=children[i];
+			if (ch!=null) {
+				AMap<K, V> m = ch.getValue();
+				if ((m!=null)&&(!m.isEmpty())) {
+					mask|=(1<<i);
+				}
+			}
 		}
+		if (mask==0xFFFF) return create(children, shift, (short) 0xFFFF, count);
+		Ref<AHashMap<K, V>>[] newChildren = Refs.filterSmallArray(children, mask);
+		return create(newChildren, shift, (short)mask, count);
 	}
 
 	/**
@@ -171,7 +173,7 @@ private static <K extends ACell, V extends ACell> AHashMap<K, V> create(Ref<AHas
 			}
 		}
 		if (mask != newMask) {
-			return new MapTree<K, V>(Utils.filterSmallArray(children, sel), shift, newMask, count);
+			return new MapTree<K, V>(Refs.filterSmallArray(children, sel), shift, newMask, count);
 		}
 		return new MapTree<K, V>(children, shift, mask, count);
 	}

convex-core/src/main/java/convex/core/data/Refs.java

@@ -190,4 +190,31 @@ private static void printTree(StringBuilder sb, Ref<ACell> ref, int indent) {
 		}
 	}
 
+	/**
+	 * Filters an array of Refs, returning an array containing only the elements where the
+	 * mask bit is set. May return the same array if all elements areincluded.
+	 *
+	 * @param arr Array to filter
+	 * @param mask Mask of elements to include
+	 * @return Filtered array.
+	 */
+	@SuppressWarnings("unchecked")
+	public static <T extends ACell> Ref<T>[] filterSmallArray(Ref<T>[] arr, int mask) {
+		int n = arr.length;
+		if (n > 32) throw new IllegalArgumentException("Array too long to filter: " + n);
+		int fullMask = (1 << n) - 1;
+		if (mask == fullMask) return arr;
+		int nn = Integer.bitCount(mask);
+		Ref<T>[] result = new Ref[nn];
+		if (nn == 0) return result;
+		int ix = 0;
+		for (int i = 0; i < n; i++) {
+			if ((mask & (1 << i)) != 0) {
+				result[ix++] = arr[i];
+			}
+		}
+		assert (ix == nn);
+		return result;
+	}
+
 }

convex-core/src/main/java/convex/core/data/SetTree.java

@@ -104,17 +104,19 @@ public static <V extends ACell> SetTree<V> create(Ref<V>[] elementRefs, int shif
 	 */
 	private static <T extends ACell> AHashSet<T> createFull(Ref<AHashSet<T>>[] children, int shift, long count) {
 		if (children.length != 16) throw new IllegalArgumentException("16 children required!");
-		Ref<AHashSet<T>>[] newChildren = Utils.filterArray(children, a -> {
-			if (a == null) return false;
-			AHashSet<T> m = a.getValue();
-			return ((m != null) && !m.isEmpty());
-		});
-
-		if (children != newChildren) {
-			return create(newChildren, shift, Utils.computeMask(children, newChildren), count);
-		} else {
-			return create(children, shift, (short) 0xFFFF, count);
+		int mask=0;
+		for (int i=0; i<16; i++) {
+			Ref<AHashSet<T>> ch=children[i];
+			if (ch!=null) {
+				AHashSet<T> m = ch.getValue();
+				if ((m!=null)&&(!m.isEmpty())) {
+					mask|=(1<<i);
+				}
+			}
 		}
+		if (mask==0xFFFF) return create(children, shift, (short) 0xFFFF, count);
+		Ref<AHashSet<T>>[] newChildren = Refs.filterSmallArray(children, mask);
+		return create(newChildren, shift, (short)mask, count);
 	}
 
 	/**
@@ -173,7 +175,7 @@ private static <V extends ACell> AHashSet<V> create(Ref<AHashSet<V>>[] children,
 			}
 		}
 		if (mask != newMask) {
-			return new SetTree<V>(Utils.filterSmallArray(children, sel), shift, newMask, count);
+			return new SetTree<V>(Refs.filterSmallArray(children, sel), shift, newMask, count);
 		}
 		return new SetTree<V>(children, shift, mask, count);
 	}

convex-core/src/main/java/convex/core/util/Utils.java

@@ -20,7 +20,6 @@
 import java.util.List;
 import java.util.Random;
 import java.util.function.Function;
-import java.util.function.Predicate;
 import java.util.function.Supplier;
 import java.util.stream.Collectors;
 
@@ -858,59 +857,6 @@ public int compare(T a, T b) {
 		});
 		return result;
 	}
-	
-	/**
-	 * Filters the array, returning an array containing only the elements where the
-	 * predicate returns true. May return the same array if all elements are
-	 * included.
-	 *
-	 * @param arr Array to filter
-	 * @param predicate Predicate to test array elements
-	 * @return Filtered array.
-	 */
-	public static <T> T[] filterArray(T[] arr, Predicate<T> predicate) {
-		if (arr.length <= 32) return filterSmallArray(arr, predicate);
-		throw new IllegalArgumentException("Can't Filter large arrays");
-	}
-
-	/**
-	 * Filters the array, returning an array containing only the elements where the
-	 * predicate returns true. May return the same array if all elements are
-	 * included.
-	 *
-	 * Array must have a maximum of 32 elements
-	 *
-	 * @param arr
-	 * @param predicate
-	 * @return
-	 */
-	private static <T> T[] filterSmallArray(T[] arr, Predicate<T> predicate) {
-		int mask = 0;
-		int n = arr.length;
-		for (int i = 0; i < n; i++) {
-			if (predicate.test(arr[i])) mask |= (1 << i);
-		}
-		return filterSmallArray(arr, mask);
-	}
-
-	@SuppressWarnings("unchecked")
-	public static <T> T[] filterSmallArray(T[] arr, int mask) {
-		int n = arr.length;
-		if (n > 32) throw new IllegalArgumentException("Array too long to filter: " + n);
-		int fullMask = (1 << n) - 1;
-		if (mask == fullMask) return arr;
-		int nn = Integer.bitCount(mask);
-		T[] result = (T[]) Array.newInstance(arr.getClass().getComponentType(), nn);
-		if (nn == 0) return result;
-		int ix = 0;
-		for (int i = 0; i < n; i++) {
-			if ((mask & (1 << i)) != 0) {
-				result[ix++] = arr[i];
-			}
-		}
-		assert (ix == nn);
-		return result;
-	}
 
 	/**
 	 * Computes a bit mask of up to 16 bits by scanning a full array for which