Ian's pfb tests #72
Replies: 7 comments 2 replies
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For some context: I'm imaging some short track (~10-15 min) MeerKAT data (L-band, 1024 channels), mainly for me to get to grips with how pfbclean works, but also hopefully to perform some useful debugging tests. I have my first image out but I'm going to wind back to the Here is my reference image from wsclean: The pfb residual seems very empty, but note that I did not use a cleaning mask, and it's obviously got into some psf-cleaning instability involving that bright off-axis source. As always I believe that masks are essential, so that could go some way to explaining it, coupled perhaps with my current lack of understanding about how to set pfb's thresholding and factor parameters: It didn't seem to produce a restored image by default, so if that's possible please let me know, otherwise I can convolve the model and sum it to the residual. I will post more findings and results here as I continue to experiement with the imager. I really like the philosophy of it and I'm looking forward to getting to grips with it. Cheers. |
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Ooh ouch, it looks like clean is doing alright (just slow) but then the flux mop step is unstable. This can sometimes happen if the PSF is not twice the size of the image but I've not seen it bomb out that badly. I have seen the peak flux increasing after a flux mop step but the rms should always decrease so I am not sure what went wrong. Does the dirty image come out looking similar to wsclean's? Did it produce a pre and post mop residual? If so, can you check if the residual looked alright before the flux mop step?
A fits mask is supported. Let me know if you run into issues with it. The idea behind the flux mop is actually to provide some sort of auto-masking because it should extract all the flux inside the current mask defined as the pixels where the model is non-zero. Looks like I may still have some work to do to get that working though.
You can make a restored image with the restore worker
Note it currently writes out image cubes, I have not yet modified it to write a fits file per imaging band. I will modify that when I get a chance.
Thanks a lot for testing. I hope it will be worth your time. I am looking into why clean is so slow #70. I already have a number of optimisations in mind. In the meantime, can I suggest that you install ducc (https://gitlab.mpcdf.mpg.de/mtr/ducc) in development mode. This should speed up gridding and FFT's because it will compile for the specific hardware you are running on |
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Reinstalled ducc and disabled flux mopping, and it was much faster this time.
Images pending... |
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The residual isn't the deepest, but the cleaning ran wild over those sidelobes which are all in the model. I'll try next with a FITS mask (hopefully I have the original wsclean one somewhere) and re-enabling flux mop. Using |
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Ah, good catch. I introduced a double normalisation by wsum in the restore worker so the residuals are there they are just very tiny. I have pushed a fix that will go in with #74. This should siginificantly seed up your cleaning when using large (> 20k) images. As discussed in #70 there was some weirdness in how I was doing the padding and fftshifting. You will hopefully have a more stable memory profile now as well |
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I'll resurrect this thread for recent adventures... |
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On the ox-box:
on nash:
Mea culpa buddy. I'll try to figure out what went wrong here... Model restoration perhaps. I still don't understand why I got two different runs on nash though, maybe some git pulls in between them. I'll keep trying. |
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As per @landmanbester's request here's the log from my first cleaning run.
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