diff --git a/mddatasetbuilder/datasetbuilder.py b/mddatasetbuilder/datasetbuilder.py
index 65d7c57..5b504f8 100644
--- a/mddatasetbuilder/datasetbuilder.py
+++ b/mddatasetbuilder/datasetbuilder.py
@@ -125,7 +125,7 @@ def __init__(
         self.clusteratom = clusteratom if clusteratom else atomname
         self.atombondtype = []
         self.stepinterval = stepinterval
-        self.nproc = nproc if nproc else cpu_count()
+        self.nproc = nproc if nproc else len(os.sched_getaffinity(0))
         self.cutoff = cutoff
         self.n_clusters = n_clusters
         self.n_each = n_each