= Name and subject of the action

Last edition: '''[[Wikinfo(changed_ts)]]''' by '''[[Wikinfo(changed_by)]]'''

The PI is responsible to closely follow the progress of the action, 
and especially to contact NEMO project manager if 
the delay on preview (or review) are longer than the 2 weeks expected.

[[PageOutline(2, , inline)]]

== Summary

||=Action       || VALID-05_mathiot_debug                        ||
||=PI(S)        || mathiot                                                 ||
||=Digest       || add a debug interface which print global min/max/sum and a simple checksum     ||
||=Dependencies || If any                                                ||
||=Branch       || source:/NEMO/branches/{YEAR}/dev_r{REV}_{ACTION_NAME} ||
||=Previewer(s) || Names                                                 ||
||=Reviewer(s)  || Names                                                 ||
||=Ticket       || #XXXX                                                 ||

=== Description

{{{#!box width=25em help
Describe the goal of development and the methodology, \\
add reference documents or publications if relevant.
}}}

''THe purpose of this action is to add a simple debug interface debug(ctxt,rvar) to print some key number if needed:
- global min/max to assess if the value are physical
- global sum to spot NaN as soon as they appears
- a checksum to catch reproducibility issue as soon as possible. In a test (change of operation order), the glob_sum catch difference 200 time step later.

The suggested check_sum is based on the idea start to appear in the bit at rank 0 and then propagate. So first you need to 'convert' a double to integer using the TRANSFERT function (print the integer corresponding to the bit pattern of the corresonding float), then each processor can do it 'local sum' of MOD(idat,ibig_prime_number) with the same modulo being used after the sum of each element. This only keep the bit from rank 0 to X (depending of the prime number choosen). Then a global sum is done.

Discussion at which level it should be implemented need to be discussed (module level, subroutine level, namelist parameter as dbg lvl or by code section (tra, dyn, zdf, sbc ...))
''

=== Implementation

{{{#!box width=35em help
Describe flow chart of the changes in the code. \\
List the Fortran modules and subroutines to be created/edited/deleted. \\
Detailed list of new variables to be defined (including namelists), \\
give for each the chosen name and description wrt coding rules.
}}}

''...''

=== Documentation updates

{{{#!box width=55em help
Using previous parts, define the main changes to be done in the NEMO literature 
(manuals, guide, web pages, …).
}}}

''...''

== Preview 

{{{#!box width=50em info
[[Include(wiki:Developers/DevProcess#preview_)]]
}}}

''...''

== Tests

{{{#!box width=50em info
[[Include(wiki:Developers/DevProcess#tests)]]
}}}

''...''

== Review

{{{#!box width=50em info
[[Include(wiki:Developers/DevProcess#review)]]
}}}

''...''