Current version

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Current version

On september, 29th 2008, an improvement was introduced on the development branch of CLASS in its data format. It was officially released in gildas dec08 version. There are now two types for the CLASS files, both based on the standard CLASS data format. Each type is associated to a new syntax of the command FILE OUT:

- FILE OUT Name MULTIPLE: File of type MULTIPLE allows to have several version of the same spectrum (same ObservationNumber).
- FILE OUT Name SINGLE: For file of type SINGLE, the ObservationNumber is a unique identifier of the spectrum: only one version exists.

The MULTIPLE type is the “historical” one for CLASS, but it has been improved, though. Inserting a new observation or a new observation version is done in a sorted list, which is a algorithm (behaving as when is large enough). The counterpart is that the list of observations is sorted when opening an output file with MULTIPLE type, but this is a minor cost compared to the subsequent gain.

The SINGLE type has been introduced to simplify and speed up On-The-Fly processing. When writing an observation, its number is automatically set such as it is unique (or it must not exist if it is provided). With this new feature, the algorithm has a dependency. This can be observed in the benchmarks performed hereafter.

Another benefit of this new type is that merging two set of observations in a SINGLE file ensures that all observations have a different number. With the historical status, or with the MULTIPLE type, two different spectra with the same number are merged under this number but with different version.