fix: nms perf (#3351)

Co-authored-by: hhstuhacker <hhstuhacker@gmail.com>

Author: lonelyclick

tfjs-core/src/backends/non_max_suppression_impl.ts

@@ -71,11 +71,15 @@ function nonMaxSuppressionImpl_(
     returnScoresTensor = false, padToMaxOutputSize = false): NamedTensorMap {
   // The list is sorted in ascending order, so that we can always pop the
   // candidate with the largest score in O(1) time.
-  const candidates =
-      Array.from(scores)
-          .map((score, boxIndex) => ({score, boxIndex, suppressBeginIndex: 0}))
-          .filter(c => c.score > scoreThreshold)
-          .sort(ascendingComparator);
+  const candidates = [];
+
+  for (let i = 0; i < scores.length; i++) {
+    if (scores[i] > scoreThreshold) {
+      candidates.push({ score: scores[i], boxIndex: i, suppressBeginIndex: 0 });
+    }
+  }
+
+  candidates.sort(ascendingComparator);
 
   // If softNmsSigma is 0, the outcome of this algorithm is exactly same as
   // before.