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- entry bus (contains initial conditions - almost not used anymore in GEM5)
- dynamic bus (contains fields which get passed from and to the dynamics)
- volatile bus (contains physics fields of which the content is not needed to calculate the next timestep)
- permanent bus (contains physics fields of which the content is needed to calculate the next timestep)
- surface bus (contains only physics fields used by the surface schemes)
Declaring a field in a bus
All fields that are in a bus need to get declared with the command "PHYVARnCx".
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The main specialty with this bus is that it is gets "differentadjusted" for each surface fraction. It always contains all surface fields but only for the points for which a certain surface scheme is valid. For example, when a land surface scheme (ISBA, SVS, CLASS) is called, this bus will only contain points with a land fraction greater than a certain threshold. By doing this one avoids nasty if-constructions inside the surface routines, checking that a point has a valid surface fraction, and the bus is more compact, without any "holes", and therefore faster to read.
Accessing fields declared in a bus
There are different ways of accessing fields declared in a bus. But they all have in common that the bus(ses) need(s) to get passed to all routines which want to access fields from the bus. The bus(ses) itself/themselves need to get passes as well as its/their length.
From the basic physics
The main physics subroutine, 'physlb1', passes the three main busses on to 'phyexe'. From there on the busses are generally named:
| Volet |
|---|
| d - dynamic bus with its length, dsiz v - volatile bus with its length, vsiz f - permanent bus with its length, fsiz |
Note that the name for the permanent bus is now 'f' and not 'p' !!!!!!!!!!
To get access to the variable names one needs to also use the module 'phybus':
| Volet |
|---|
| use phybus |
From the surface schemes
In the surface one passes the surface bus, its size, the list of variable and its size to the surface routine.
Explain what a bus is: slab with just land points etc.
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