Annotation of /MITgcm/pkg/atm_ocn_coupler/NOTES

Issues with the current coupler:

It should have been written in C.

It should have more "safe mode" timeout options. For example
poll for receiver ready before sending to catch deadlocks.
Poll for receive and trap too many spins waiting
for an event.

There is only one coupler.
Coupler has no concept of being "tiled" itself. A heirarchical
structure of coupled "couplers" could be envisioned.
Only one tile set per process can be registered.

No real support for multi-threaded codes.

Coupler itself is pure sequential

The coupler only supports transfer of two-dimensional fields.

Wrong name errors are not trapped clearly.

Consistency between components is hard to validate.

Coupled setup consists of a coupling layer plus one or more component
models and communications API for talking between the coupling
layer and the components. 

Coupling layer really provides two functions

1. An limited form of associative storage into which component models can export 
   data and from which component models can import data.  Data is exported
   and imported using a text string to identify it. Abstraction is similar 
   to that of a simple file system. There are implicit synchronisation
   rules that need to be adhered to. Could be extended to allow file system
   access and/or http based communication.

2. Extrapolation and interpolation modules which are used to map
   data between component models having differing grids.

 Associative Storage Function
 ============================
 Data is exported and imported using a text string to identify it. Abstraction 
 is similar to that of a simple file system. In the current coupler 
 implementation there are implicit synchronisation rules that need to be 
 adhered to. A component model cannot asynchronously request data. Could be 
 extended to allow file system access and/or http based communication.

 Extrapolation and interpolation
 ===============================
 This maps data between different representations.
1	jmc	1.1	Issues with the current coupler:
2
3			It should have been written in C.
4
5			It should have more "safe mode" timeout options. For example
6			poll for receiver ready before sending to catch deadlocks.
7			Poll for receive and trap too many spins waiting
8			for an event.
9
10			There is only one coupler.
11			Coupler has no concept of being "tiled" itself. A heirarchical
12			structure of coupled "couplers" could be envisioned.
13			Only one tile set per process can be registered.
14
15			No real support for multi-threaded codes.
16
17			Coupler itself is pure sequential
18
19			The coupler only supports transfer of two-dimensional fields.
20
21			Wrong name errors are not trapped clearly.
22
23			Consistency between components is hard to validate.
24
25			Coupled setup consists of a coupling layer plus one or more component
26			models and communications API for talking between the coupling
27			layer and the components.
28
29			Coupling layer really provides two functions
30
31			1. An limited form of associative storage into which component models can export
32			data and from which component models can import data. Data is exported
33			and imported using a text string to identify it. Abstraction is similar
34			to that of a simple file system. There are implicit synchronisation
35			rules that need to be adhered to. Could be extended to allow file system
36			access and/or http based communication.
37
38			2. Extrapolation and interpolation modules which are used to map
39			data between component models having differing grids.
40
41			Associative Storage Function
42			============================
43			Data is exported and imported using a text string to identify it. Abstraction
44			is similar to that of a simple file system. In the current coupler
45			implementation there are implicit synchronisation rules that need to be
46			adhered to. A component model cannot asynchronously request data. Could be
47			extended to allow file system access and/or http based communication.
48
49			Extrapolation and interpolation
50			===============================
51			This maps data between different representations.