This is pure speculation, but I have been trying to find documentation for the sandboxing for a while (unsuccessfully), and I wonder whether this might be the issue? Memory mapping seems very likely to be restrictable, and there's nothing in /usr/share/sandbox/xgridagentd_*.sb which would appear to allow it. If that is the problem, you could try either finding some documentation (good luck!) or changing (deny default) to (allow default) - if that works it would completely undermine the sandboxing, but hey, if it's a private cluster...
I'd be interested to know if that's the problem.
Cheers,
Richard.
> 6. Successfully reports memory mapping the above file (as judged from the error returns) and *problematically* performs math on the data.
>
> That last is the problem. When the program is run directly on the head node via the command-line, it performs flawlessly every time. (or for that matter, on another stand-alone machine.) But when run remotely via Xgrid, the file remains all zeroes, no data written to it. (Actually, once it came back with all zeroes until the last few megabytes, then the data was correctly written. This caused me to wonder if the file pointer being at the end of the file when I mapped it was an issue. So I closed the file after creating and initializing it, then opened it again before mapping it. The file came back all zeroes.)
>
> So, is there a known problem with Xgrid and memory mapping? I would hate to give it up for the following reason: while the XSAN is so fast that memory mapping doesn't provide much of a speed boost, I was hoping eventually to allow simultaneous mapping of different sections of the file from multiple versions of the program all running on the grid. Thus version 1 could analyze data points 1-1,000,000, version 2 could analyze 1,000,001-2,000,000, etc.
>
> And, yes, we have thousands of these 650 MB files...
>
> Thanks in advance for the help!
> Mark Spano
> Bioengineering Dept.
> Arizona State University
>
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