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FAQs - Frequently asked questions | ||
================================= | ||
| **Q:** How do I know what order to put the parameter values in the pytorch | ||
tensor which gets passed to the simulator? | ||
| **A:** If you are using any ``Module``` object (so a simulator), then you can | ||
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||
**Q:** How do I know what order to put the parameter values in the pytorch tensor which gets passed to the simulator? | ||
----------- | ||
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**A:** If you are using any ``Module``` object (so a simulator), then you can | ||
get the parameters using ``print(simulator)``. The order of the dynamical | ||
parameters (top to bottom) corresponds to the order you should use in your | ||
parameter value tensor. Note that you can ignore the static parameters. | ||
| **Q:** Why can I put the lens redshift at higher values than the source | ||
redshift or to negative values for some parametric models? | ||
| **A:** We can calculate everything for those profiles with reduced deflection | ||
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**Q:** Why can I put the lens redshift at higher values than the source redshift or to negative values for some parametric models? | ||
----------- | ||
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**A:** We can calculate everything for those profiles with reduced deflection | ||
angles where the redshifts do not actually play into the calculation. If you use | ||
a profile defined by the lens mass, like a NFW lens, or a Multiplane lens then | ||
it does matter that the redshifts make sense and you will very likely get errors | ||
for those. Similarly, if you call the ``lens.physical_deflection_angle`` you | ||
will encounter errors. | ||
| **Q:** I do (multiplane-)lensing with pixelated convergence using the | ||
pixelated kappa map of a parametric profile. The lensing effect differs from | ||
directly using the parametric lens. Why is the lensing effect different? | ||
| **A:** Since you do pixelated convergence your mass is binned in pixels in a | ||
finite field of view (FOV) so you are missing some mass. At the limit of | ||
infinite resolution and infinite FOV the pixelated profile gives you the | ||
parametric profile. If the difference is above your error tolerance then you | ||
have to increase the resolution and/or FOV of your pixelated convergence map. | ||
Especially for SIE or EPL profiles (which go to infinity density in the | ||
center, and have infinite mass outside any FOV) you will miss infinite mass | ||
when pixelating. | ||
|
||
**Q:** I do (multiplane-)lensing with pixelated convergence using the pixelated kappa map of a parametric profile. The lensing effect differs from directly using the parametric lens. Why is the lensing effect different? | ||
----------- | ||
|
||
**A:** Since you do pixelated convergence your mass is binned in pixels in a | ||
finite field of view (FOV) so you are missing some mass. At the limit of | ||
infinite resolution and infinite FOV the pixelated profile gives you the | ||
parametric profile. If the difference is above your error tolerance then you | ||
have to increase the resolution and/or FOV of your pixelated convergence map. | ||
Especially for SIE or EPL profiles (which go to infinity density in the | ||
center, and have infinite mass outside any FOV) you will miss infinite mass | ||
when pixelating. |