Investigate the need/use of ADFH_MAXIMUM_FILES 128


Interesting development. I just tried to open more than 128 CGNS files using the 3.1.4 MLL… It stops at 128 files.

I just searched the MLL code for the cgio error message, and I quickly found this 128 file limit… See in src/ADFH.c around line 170-ish:


This line is the source of my open file limit problem I discussed below…

Hi Scot,

Just to clarify that I have learned at this point. There appear to be two limits we are dealing with here:

1) A limit on the number of “distinct” CGNS files that can be open at any one time (via cg_open())
a. This seems to currently be set to 128 in the MLL (per my prior email below).
b. Note: CGNS MLL v2.5 did not have this limit and was only subject to OS file handle limit.

2) A limit on the number of simultaneous OS file handles that the MLL can have open at any time.
a. Limit controlled by OS & system admins - Per our prior discussion, this can easily be adjusted up from default of (e.g.) 1024.
b. A single CGNS file may internally link many “slave” CGNS files, up to the OS file handle limit, not the CGNS limit of 128.

So, my code was not previously distinguishing these two file limit scenarios, as I didn’t know there was a difference. I had just assumed that the “link” file count limit was the same as the “cg_open” limit (which is 128), so I had overly restricted our linking capability (which we increasingly need).




Scot Breitenfeld

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