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Keywords: speed 4.3.2 4.4.0 examples n02 n03
Forum: Documentation and Examples
Re: Question speed differences between 4.4.0 and 4.3.2 with examples... (Frank Schwamm)
Date: 15 Feb, 2002
From: Gabriele Cosmo <Gabriele Cosmo>

Hi Frank,

several reasons explain the performance degradation you noticed from
release 3.2 to release 4.0.
Definitely, one thing that will already help and you should do, is to
apply patch-01 to release 4.0 that you can download from the web.
However, there're other issues which make 4.0 slower than 3.2 and we
are tracing them all:
- 4.0 uses CLHEP-1.7, we experienced a serious performance degradation
  in handling 3/4-vectors in this new version of CLHEP. These issues
  have been reported to CLHEP editors and they're working to fix this;
- if you're testing on a Linux box, the setup for Linux-g++ has changed
  since 3.2 to adopt ANSI C++ setup. We noticed a slight penalty for
  this as well;
- 4.0 includes a new mechanism for handling touchables in the geometry,
  which are now reference-counted. We know a 5% penalty (in the worst
  cases) is due to this;
- 4.0 EM physics includes a more precise algorithm for multiple
  scattering, which in some cases may lead up to 10% performance loss;
- a new mechanism for handling cuts in range is implemented in 4.0,
  that we identified is not yet optimally tuned.

We're currently working for cleaning this penalty and even optimising
the overall performance. We plan to distribute a second patch by end of
February which also will deal with most of these issues.

Cheers, Gabriele

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