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On the HSC side, we have two driver tasks for coaddition and mulitband multiband processing that use parallel processing primitives that aren't yet available on the LSST side. These combine DetectCoaddSourcesTask with MakeCoaddTempExpTask and AssembleCoaddTask (so we only have to write one coadd image, as noted above), and then combine the rest of these into a single driver. I'd eventually like to get to a similar position on the LSST side, but I think the transfer or reimplementation of those parallel processing primitives is a separate issue, so for now I'm assuming we'll just transfer all of these tasks individually. They'll still have the same functionality, but they'll rely more on I/O for communication and require more human intervention.
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