1. Reorganization of ReadoutElements: goal – optimize data access (algorithm timing!)
Mdt example
now:
MdtReadoutElement = 1 multilayer
MdtPrepDataCollection contains data corresponding to 2 MdtReadoutElements
for rel. 14.x.0
keep MdtReadoutElements
purely readout geometry – no link to raw geometry volumes
add MdtDetectorElements
holding pointers to 2 MdtReadoutElements
MdtPrepDataCollection contains data corresponding to 1 MdtDetectorElement
First implementation

2. Reorganization of ReadoutElements: goal – optimize data access (algorithm timing!)
test algorithm with a old and new-style access to tube center
use callgrind for algorithm profiling
3.04% of Job cpu for processCollectionOld
1.24% manager->getMdtReadoutElement [identifier decoding]
0.83% MdtReadoutElement->center(Identifier) [identifier decoding]
1.49% of job cpu for processCollection
1.01% MdtDetectorElement->center(Identifier)
0.xx% x 3 MdtIdHelper->multilayer/tubeLayer/tube(Identifier)
0.34% MdtReadoutElement->center(tubeLayer, tube)
MuonGeoModel in opt mode gain 50%
test is sensitive only if GeoModel cache is filled init time
more details in

3. Clash survey
Dennis Wright recently joined the Atlas Simulation team and started a systematic survey of the Muon Geometry clashes in the ideal layout (R01)
concentrating on active volumes as a start
identified several small clashes ~0.1nm between nearby volumes (shared boundaries)
introduced small tolerances removing the problems
fixes will go in
possibly he will take care of implementing cutouts in active volumes