From 2183765fd615b6402cb80c36f50ef0baa3fb6d92 Mon Sep 17 00:00:00 2001
From: Matthias Wolf <matthias.wolf@cern.ch>
Date: Mon, 9 Feb 2015 22:29:42 +0100
Subject: [PATCH] Allow for more than 3 skipped LHE files.

Currently, the LHESource reads by calling nextEvent(), which in turn
calls LHEReader::next().  The latter method returns an empty reference
at the end of a file [1].

When reading an event in a fourth file, nextEvent() is first called in
the constructor of LHESource [2], returning an empty reference at the
end of the fist file.  The other calls to nextEvent(), [3] and [4],
return an empty reference at the end of the second and third file.
But there is a check after [4], and LHESource quits reading files
without attempting to open the fourth file.

Try to address the situation by keeping reading files as long as new
files are opened and empty events are returned.  This potentially also
removes the need for the check after [4].

Also pertains to dmwm/CRABServer#4659.

[1]: http://cmslxr.fnal.gov/lxr/source/GeneratorInterface/LHEInterface/src/LHEReader.cc#0491
[2]: http://cmslxr.fnal.gov/lxr/source/GeneratorInterface/LHEInterface/plugins/LHESource.cc#0042
[3]: http://cmslxr.fnal.gov/lxr/source/GeneratorInterface/LHEInterface/plugins/LHESource.cc?v=CMSSW_7_4_0_pre5#0166
[4]: http://cmslxr.fnal.gov/lxr/source/GeneratorInterface/LHEInterface/plugins/LHESource.cc?v=CMSSW_7_4_0_pre5#0169
---
 GeneratorInterface/LHEInterface/plugins/LHESource.cc | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/GeneratorInterface/LHEInterface/plugins/LHESource.cc b/GeneratorInterface/LHEInterface/plugins/LHESource.cc
index 2a9c0b2c0cd76..df894608210b5 100644
--- a/GeneratorInterface/LHEInterface/plugins/LHESource.cc
+++ b/GeneratorInterface/LHEInterface/plugins/LHESource.cc
@@ -64,8 +64,11 @@ void LHESource::nextEvent()
 		return;
         }
 
-	bool newFileOpened = false;
-	partonLevel = reader->next(&newFileOpened);
+	bool newFileOpened;
+	do {
+		newFileOpened = false;
+		partonLevel = reader->next(&newFileOpened);
+	} while (newFileOpened && !partonLevel);
 
 	if (!partonLevel) {
 		return;