From 7e8e717423c5be35636fb4cadc394955c4c74180 Mon Sep 17 00:00:00 2001
From: Deepak Cherian <deepak@cherian.net>
Date: Sat, 20 Jan 2024 15:23:35 -0700
Subject: [PATCH] Add threshold

---
 flox/core.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/flox/core.py b/flox/core.py
index c7455a05a..cdb2b4ab8 100644
--- a/flox/core.py
+++ b/flox/core.py
@@ -260,7 +260,8 @@ def chunk_unique(labels, slicer, nlabels, label_is_present=None):
         uniques = ilabels[label_is_present[:-1]]
         return uniques
 
-    if nlabels < approx_chunk_size:
+    if nlabels < 5 * approx_chunk_size:
+        logger.debug("Using threadpool since %s < 5 * %s", nlabels, approx_chunk_size)
         with ThreadPoolExecutor() as executor:
             futures = [
                 executor.submit(chunk_unique, labels, slicer, nlabels)