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Note that only calls to other module modules are asynchronous in this way - the functions internal to the Macro language (see List of Operators and Functions) are part of the Macro module and are therefore not farmed out to the other modules. As a rule of thumb, Macro function calls which relate to an icon (e.g. Cross Section Data, Observation Filter) will be called asynchronously.
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Although Metview's own internals do not use threading, Metview relies on several libraries for some of its work. Magics is used for plotting, and employs multiple threads when plotting contours. When regridding GRIB data through the Mars Retrieval or the GRIB Filter icon, Metview uses Emoslib; although this package is not multi-threaded, Metview will in the future use the new interpolation package, which will use multiple threads.
Temporary files
To avoid the use of temporary files in large Macro computations, see Vectors.