From 24ddfae76d308d86f98bcd4bd5e87841c3be2b0f Mon Sep 17 00:00:00 2001
From: Jürgen Knödlseder <jurgen.knodlseder@irap.omp.eu>
Date: Fri, 12 Feb 2016 00:31:58 +0100
Subject: [PATCH] Delete any existing event list in ctobssim before appending new simulated events.

---
 ChangeLog                 |  1 +
 NEWS                      |  6 +++++-
 src/ctobssim/ctobssim.cpp | 13 +++++++++++--
 3 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 5996754..96c3e74 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -3,6 +3,7 @@
         * Version 1.1.0 released
         ========================
 
+        Delete existing events before simulation in ctobssim (#1663)
         Add csiactcopy script (#1661)
         ctselect allows usage of non-default events and GTI extensions (#1598)
 
diff --git a/NEWS b/NEWS
index 20d9b33..e164696 100644
--- a/NEWS
+++ b/NEWS
@@ -28,7 +28,11 @@ None
 
 5. ctobssim - CTA observation simulation
 ----------------------------------------
-None
+Any existing events in an event list are now removed before starting the
+simulation to enable providing an existing event file on input from which
+only the observation attributes are extracted (for example GTI, ROI, energy
+range, etc.) while the measured events are replaced by the simulated ones
+(#1663).
 
 
 6. ctselect - CTA event selection
diff --git a/src/ctobssim/ctobssim.cpp b/src/ctobssim/ctobssim.cpp
index 3d9c721..7ec7450 100644
--- a/src/ctobssim/ctobssim.cpp
+++ b/src/ctobssim/ctobssim.cpp
@@ -1,7 +1,7 @@
 /***************************************************************************
  *                  ctobssim - Observation simulator tool                  *
  * ----------------------------------------------------------------------- *
- *  copyright (C) 2011-2015 by Juergen Knoedlseder                         *
+ *  copyright (C) 2011-2016 by Juergen Knoedlseder                         *
  * ----------------------------------------------------------------------- *
  *                                                                         *
  *  This program is free software: you can redistribute it and/or modify   *
@@ -360,6 +360,14 @@ void ctobssim::run(void)
                 continue;
             }
 
+            // Remove now all events from the event list but keep the
+            // event list information such as ROI, Good Time Intervals,
+            // energy boundaries. This will also keep additional columns
+            // in an event list file.
+            GCTAEventList* events =
+                static_cast<GCTAEventList*>(const_cast<GEvents*>(obs->events()));
+            events->remove(0, events->size());
+
             // Work on a clone of the CTA observation. This makes sure that
             // any memory allocated for computing (for example a response
             // cache) is properly de-allocated on exit of this run
@@ -407,7 +415,8 @@ void ctobssim::run(void)
                 // to avoid multiple threads writing simultaneously
                 #pragma omp critical
                 {
-                    obs_clone.save(outfile, clobber());
+                    //obs_clone.save(outfile, clobber());
+                    obs->save(outfile, clobber());
                 }
 
                 // Dispose events
--
libgit2 0.21.4