diff --git a/config_example.py b/config_example.py
index 0ac65ad..c2f7fcf 100644
--- a/config_example.py
+++ b/config_example.py
@@ -20,6 +20,10 @@ dumpXML = 1
 visualization = 1
 logLevel = logging.INFO
 
+# number of parallel workers. -1: all cores; 1: sequential
+# for more details, see joblib.Parallel
+numJobs = 3
+
 # Number of simulation runs with the same parameters for statistical relevance
 runs = range(10)
 
diff --git a/study.py b/study.py
index 914acfe..f557fc2 100644
--- a/study.py
+++ b/study.py
@@ -50,7 +50,8 @@ def study():
     sim.logger.info("Starting simulations:", extra=sim.format)
     start = time.time()
 
-    results = Parallel(-1)(delayed(runOnce)(sim, config, shape) for shape in config.nextShape())
+    results = Parallel(config.numJobs)(delayed(runOnce)(sim, config, shape) for shape in config.nextShape())
+
 
     end = time.time()
     sim.logger.info("A total of %d simulations ran in %d seconds" % (len(results), end-start), extra=sim.format)