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In terms of how this plays with the filesystem cache, and hdf5 cache, the filesystem will cache the original data in the hdf5 - so if you revisit cspad from the same chunk, the compressed data may be cached by the filesystem, but hdf5 will have to decompress the whole chunk again. Now hdf5 maintains it's own chunk cache which stores recently used chunks (uncompressed). There is one cache global cache, but one can also create caches on a per dataset basis. The Translator creates datasets with a cache to hold 3 chunks - so a 300MB cache for a cspad dataset. This information is available to any program that reads the hdf5 file, but whether or not it is used is unclear. A high level program that reads the file - like hdffor the library overais in the filIf you are writing your own program to read an hdf5 file, you can set the overall chunk cache, as well as per dataset cache's explicitly.

There are options with translation to control the objects per chunk. One can also turn off compression when translating.

TimeTool

Here we cover topics specific to the offline TimeTool module. The TimeTool results can be obtained in one of two ways depending on the experimental setup. The first is directly during data acquisition, the second is during offline analysis using the psana module TimeTool.Analyze. Regrading data acquisition, for data recorded prior to Oct 13, 2014, the timetool results were always recorded as EPICS PV's. After Oct 13, 2014, they are still recorded as EPICS PV's, but also recorded in their own data type: TimeTool::DataV*. The version increments as the time tool develops. For data recorded up to around November 2014, this was DataV1. Around December of 2014 it changed to DataV2. The preferred method of accessing the data is through the high level DataV* objects, but users must take care to use the correct type. EPICS PV's are still provided for backward compatibility. Regarding offline analysis with the TimeTool.Analyze psana module, similarly to the experiment data files, this module puts a TimeTool::DataV* object in the event store depending on the version of the software. The initial versions of the software put a collection of floats, or ndarrays in the event store (for backward compatibility, it still puts the floats in the event store). Documentation on the psana TimeTool modules can be found in the psana - Module Catalog.

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