Fix Version/s: None
Component/s: meas_algorithms, pipe_tasks
For DESC, I have built an "online coaddition" class that is a replacement for afw.statisticsStack written in pure python/numpy that can do mean and clipped mean stacks using a running sum. This results in significant memory savings vs statisticsStack and does not require reading sub-regions. Tests on ci_hsc show it is 15-20% faster than statisticsStack for mean coaddition (due to reduced overhead), but it is slower for clipped means (in a way that scales with number of images) due to the increased i/o.
This code currently lives at https://github.com/lsst/pipe_tasks/tree/u/erykoff/onlinecoadd . The AccumulatorMeanStack class will be put in meas_algorithms, a more appropriate location. Changing to the online coaddition code in AssembleCoaddTask will be configured with a doOnlineCoaddition config option that will only apply to "MEAN" and "MEANCLIP" coadds.
Also: upon further review, when working on the tests, I realized that the MEANCLIP option would not work without an online median statistic option, and this is not trivial. Therefore, this ticket is only for straight MEAN statistics.
PRs are https://github.com/lsst/meas_algorithms/pull/251 and https://github.com/lsst/pipe_tasks/pull/551