diff --git a/swash/config.ini b/swash/config.ini
index 171f312..490e6c2 100644
--- a/swash/config.ini
+++ b/swash/config.ini
@@ -14,6 +14,7 @@ out=out_data
 input=sws/INPUT.sws
 swashrun=/opt/swash/swash/swashrun
 out=out
+mpi=4
 
 [post]
 out=out_post
diff --git a/swash/processing/swash.py b/swash/processing/swash.py
index 0493c64..8d7bb93 100644
--- a/swash/processing/swash.py
+++ b/swash/processing/swash.py
@@ -28,6 +28,11 @@ if out.exists():
 with tempfile.TemporaryDirectory(prefix="swash_", dir=".") as tmp_raw:
     tmpdir = pathlib.Path(tmp_raw)
 
+    if config.hasoption("swash", "mpi"):
+        mpi = ("-mpi", config.getint("swash", "mpi"))
+    else:
+        mpi = ()
+
     log.info(f"Copying files to '{tmpdir}'")
     shutil.copy2(inp, tmpdir)
     shutil.copytree(
@@ -36,7 +41,7 @@ with tempfile.TemporaryDirectory(prefix="swash_", dir=".") as tmp_raw:
     with open(tmpdir.joinpath("sws.log"), "w") as logfile:
         log.info(f"Runing swash in '{tmpdir}'")
         subprocess.run(
-            (config.get("swash", "swashrun"), "-input", inp.name),
+            (config.get("swash", "swashrun"), "-input", inp.name, *mpi),
             cwd=tmpdir,
             stdout=logfile,
             stderr=logfile,