Address possible NaN in ExactSbend & ChrUniformAcc #789
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cemitch99
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bug
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Found two examples that illustrate the original problem and this fix. Just trying to decide what works best for testing. |
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ax3l
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ax3l
approved these changes
Jan 25, 2025
SchroederSa
reviewed
Jan 25, 2025
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| In this test, the initial values of :math:`\sigma_x`, :math:`\sigma_y`, :math:`\sigma_t`, :math:`\epsilon_x`, :math:`\epsilon_y`, and :math:`\epsilon_t` must agree with nominal values. | ||
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| In addition, the fraction of charge that is lost must agree with the nominal value of 7.7754%, to within a specified tolerance. |
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It's a bit unclear where the number 7.7754% is coming from.
| # add beam diagnostics | ||
| monitor = elements.BeamMonitor("monitor", backend="h5") | ||
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| # design the accelerator lattice) |
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Little typo: ')' at the end of the line
| amrex::ParticleReal const ptf_tot2 = std::pow(ptf_tot,2); | ||
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| // check whether particle lies within the domain of map definition | ||
| if (pti_tot2 <= 1_prt || ptf_tot2 <= 1_prt) { |
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Just a question: Are there coding practices on what to put in an 'if' clause and what in a 'else' clause? I would have naively thought the if(XXX) is testing the good / default case and the 'else:' handling the exception.
Thanks!
| bunch_charge_C = 1.0e-9 # used with space charge | ||
| npart = 10000 # number of macro particles | ||
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| # reference particle |
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There are an irregular number of spaces in line 28 and 32 after the '# '
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This PR addresses the special case when the square root appearing in the nonlinear map for the ExactSbend element becomes negative -- due, for example, to numerical roundoff.
A similar restriction of the domain of map definition appears for the ChrAcc element, and this is also addressed here. A modified cyclotron example is added with increased energy spread to illustrate the possibility of particle loss.
Fix #599 .
Follow-up: Check for any additional (nonlinear) elements that require further restrictions on the domain of definition to avoid nan's.