diff --git a/test/sort_hddm.py b/test/sort_hddm.py
new file mode 100755
index 0000000..53bace3
--- /dev/null
+++ b/test/sort_hddm.py
@@ -0,0 +1,87 @@
+#!/usr/bin/env python3
+
+import sys
+import hddm_s
+import hddm_r
+
+max_eventNo = 10000000000
+max_readbuf = 1000
+eventNo = 1
+xmlout = 0
+clean = 0
+rest = 0
+
+readbuf = {}
+
+narg = 1
+while narg < len(sys.argv):
+   if sys.argv[narg] == "-n":
+      max_eventNo = int(sys.argv[narg + 1])
+      narg += 2
+      print(f"stopping after {max_eventNo} events")
+   elif sys.argv[narg] == "-x":
+      xmlout = 1
+      narg += 1
+   elif sys.argv[narg] == "-c":
+      clean = 1
+      narg += 1
+   elif len(sys.argv[narg]) > 2 and sys.argv[narg][:2] == "-n":
+      max_eventNo = int(sys.argv[narg][2:])
+      print(f"stopping after {max_eventNo} events")
+      narg += 1
+   else:
+      break
+
+def getPhysicsEvents(rec):
+   if rest == 0:
+      return rec.getPhysicsEvents()
+   else:
+      return rec.getReconstructedPhysicsEvents()
+
+for fin in sys.argv[narg:]:
+   finhead = open(fin, 'r').readline()
+   if '<HDDM class="s" ' in finhead:
+      rest = 0
+      fini = hddm_s.istream(fin)
+      fout = hddm_s.ostream("sort_hddm.hddm")
+      if xmlout > 0:
+         xout = open("sort_hddm.xml", 'w')
+   elif '<HDDM class="r" ' in finhead:
+      rest = 1
+      fini = hddm_r.istream(fin)
+      fout = hddm_r.ostream("sort_hddm.hddm")
+      if xmlout > 0:
+         xout = open("sort_hddm.xml", 'w')
+   else:
+      print(f"input file {fin} has unknown data format, skipping...")
+      continue
+   for rec in fini:
+      for pev in getPhysicsEvents(rec):
+         if clean > 0:
+            pev.deleteHitViews()
+         if pev.eventNo == eventNo:
+            if clean > 0:
+               for rea in pev.getReactions():
+                  rea.deleteVertices(-1,1)
+            fout.write(rec)
+            if xmlout > 0:
+               xout.write(rec.toXML())
+            if eventNo % 100 == 0:
+               print("wrote event", eventNo)
+            eventNo += 1
+            while eventNo in readbuf and eventNo < max_eventNo:
+               fout.write(readbuf[eventNo])
+               if xmlout > 0:
+                  xout.write(readbuf[eventNo].toXML())
+               if eventNo % 100 == 0:
+                  print("wrote event", eventNo)
+               del readbuf[eventNo]
+               eventNo += 1
+            if eventNo == max_eventNo:
+               sys.exit(0)
+         else:
+            readbuf[pev.eventNo] = rec
+            if len(readbuf) > max_readbuf:
+               print("readbuf backed up with", len(readbuf), "waiting events")
+               print("giving up, sorry.")
+               sys.exit(1)