Avoid modifying the input pixel array in place in wcs_pix2world#19859
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astrofrog wants to merge 3 commits into
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Avoid modifying the input pixel array in place in wcs_pix2world#19859astrofrog wants to merge 3 commits into
astrofrog wants to merge 3 commits into
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…fsetting a bounded scratch buffer instead
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I wonder if maybe it's best to not backport and to just say that we are going to focus on thread-safety issues for 8.1.0 |
mhvk
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Jun 4, 2026
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This looks good! Two totally nitpicky comments, which can definitely be ignored.
| npy_intp block = ncoord; | ||
| double* pixscratch = NULL; | ||
| if (delta != 0.0 && ncoord > 0) { | ||
| block = (ncoord < 1024) ? ncoord : 1024; |
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Since you have access to numpy headers, you could use NPY_BUFSIZE here -- which ends up being the same (it is 8192 bytes).
| double* pixscratch = NULL; | ||
| if (delta != 0.0 && ncoord > 0) { | ||
| block = (ncoord < 1024) ? ncoord : 1024; | ||
| pixscratch = (double*)malloc((size_t)block * nelem * sizeof(double)); |
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Is nelem typically 2? I'd tend to make the scratch size independent of its value.
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This is a fix for #16244 and an alternative to #16459
The basic idea here is that instead of modifying the input array in-place (which is very thread-unsafe), we iterate over the coordinates in blocks of 1024 elements. This size was chosen as it results in essentially no measurable overhead - it's an optimal value that is not too small yet fits in a typical L1 cache.
When origin=1, the block size is just the number of coordinates and there is no chunking necessary.
Fixes #16244