belliottsmith commented on code in PR #207:
URL: https://github.com/apache/cassandra-accord/pull/207#discussion_r2185127951
##########
accord-core/src/main/java/accord/utils/SortedArrays.java:
##########
@@ -1793,4 +1794,29 @@ private static void swap(int[] values, int i, int j)
values[i] = values[j];
values[j] = t;
}
+
+ public static <T extends Comparable<? super T>> BitSet
toBitSet(SortedArrays.SortedArrayList<T> src,
+
SortedArrays.SortedArrayList<T> subset)
+ {
+ BitSet bitSet = new BitSet(src.size());
+ for (int i = 0; i < src.size(); i++)
+ {
+ if (subset.contains(src.get(i)))
Review Comment:
we should use `foldlIntersection` for O(n) versus O(n.lg(n)) complexity
e.g.
`return foldlIntersection(superset.array, 0, superset.array.length,
subset.array, 0, subset.array.length, (i, bs, li, ri) -> { bs.set(li); return
bs; }, new SimpleBitSet(superset.size()));`
This does require copying foldlIntersection to support operating over
objects rather than long:
```
@Inline
public static <T extends Comparable<? super T>, V> V
foldlIntersection(T[] as, int ai, int alim, T[] bs, int bi, int blim,
IndexedFoldIntersect<? super T, V> fold, V accumulate)
{
return foldlIntersection(1, Comparable::compareTo, as, ai, alim, bs,
bi, blim, fold, accumulate);
}
@Inline
public static <T, V> V foldlIntersection(int aiMatchIncrement,
AsymmetricComparator<? super T, ? super T> comparator, T[] as, int ai, int
alim, T[] bs, int bi, int blim, IndexedFoldIntersect<? super T, V> fold, V
accumulate)
{
while (true)
{
long abi = findNextIntersection(as, ai, alim, bs, bi, blim,
comparator);
if (abi < 0)
break;
ai = (int)(abi);
bi = (int)(abi >>> 32);
accumulate = fold.apply(as[ai], accumulate, ai, bi);
ai += aiMatchIncrement;
++bi;
}
return accumulate;
}
```
and copying IndexedFoldIntersectToLong to IndexedFoldIntersect:
```
package accord.utils;
public interface IndexedFoldIntersect<P1, Accumulate>
{
/**
* Apply some merge function accepting a constant object parameter p1,
and the prior output of this function
* or the initial value, to some element of a collection, with the index
of the element provided.
*
* This function is used for efficiently folding over some subset of a
collection.
*/
Accumulate apply(P1 p1, Accumulate p2, int leftIndex, int rightIndex);
}
```
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