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Practical Suggestion for Setting Up a Large Bank of Filters:

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We have carefully explained (how to avoid) a number of the pitfalls in computing post-Newtonian chirps. Before using the chirp generators to spit out hundreds or thousands of chirps needed for a bank of filters and farming out the computations out to dozens of parallel processors in a massive coalescing binary search, we strongly suggest that you edit the examples already given and check the routine against the three extreme cases you will encounter in your search.

  1. Try the example with both masses set to the minimum mass in your proposed search, i.e. compute the phase and frequency evolution and the chirps for the template in the upper right hand corner in figure [*]. This is the template of longest duration. If you are going to have a memory allocation problem you will have it with this template. Also, knowing the duration of the longest template in your search will help you decide the length of the segments of data which you filter. In general, you want the length of these data segments to be at least several times longer than the longest chirp. See Section [*] for further details.
  2. Try the chirp generator with both masses set to the maximum mass in your search, i.e. compute the phase and frequency evolution of the template in the lower left corner of figure [*]. This is the shortest duration template and the one least likely to make it to the upper cut off frequency before going out of the region of post-Newtonian viability. This case will be the most demanding test of the ``chirp-termination'' logic in phase_frequency(). It is also possible in the case of extremely large masses that there really is no chirp at all in the frequency regime requested. For example a binary composed of two 100$M_\odot$ object will coalesce long before it reaches the initial chirp frequency of the 60Hz we are using as our a lower cutoff frequency in our example. Don't worry. The routine phase_frequency() will warn you that the root finder was unable to find a viable solution for the initial time. You may have to adjust the search range accordingly.
  3. Try the chirp generator with one mass at the minimum allowed value and the other mass at the maximum allowed value, i.e. compute the phase and frequency evolution for the template in the upper left corner of figure [*]. This is the template which is most dominated by post-Newtonian terms in the evolution.
If the routine gives satisfactory results for these three cases, it should work for all the cases shown in figure [*]; you are now ready for wholesale production.


next up previous contents
Next: Additional contributions to the Up: GRASP Routines: Gravitational Radiation Previous: Example: filters program   Contents
Bruce Allen 2000-11-19