Computation time optimisation

This issue was created automatically from an original CUE issue. Further discussion may take place here.

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I identified this problem in a Telemac-2D computation but it's similar for 3D and maybe other modules.
When using Atmospheric binary data file in Selafin format, we're facing an increase of time computing.
In fact at each time step, when we compute the interpolated value in time, I noticed that we always searching the record time surrounding the requested time and we always read the record values at those both time.
As we are in an always increase time we could imagine to store surrounding time and values and just read a new record when it's needed by computation.
This will save a lot of time as meteorological file are often hourly based (1, 3 or 6h) and computation time step are around few seconds.
In addition, it could be great to automatically manage the initial date and time value of the atmospheric data file to find the right moment for the interpolation rather than adding a time shift if we run a simulation which use a long meteo file...