Comment 8 for bug 1218842

Thanks a lot for the investigation.

Cheers,

Olivier
On Nov 27, 2013, at 10:29 PM, Pavel Demin <email address hidden> wrote:

> I've just looked at the mcfio/stdhep code includedd with the pythia-pgs
> package in MG5.
>
> The code in pythia-pgs/src/pythia.f calls the following chain of
> functions to write an event:
>
> 1. stdxwrt defined in pythia-pgs/libraries/PGS4/src/stdhep-dir/src/stdhep/stdxwrt.F
> 2. stdxwevt defined in pythia-pgs/libraries/PGS4/src/stdhep-dir/src/stdhep/stdxwevt.F
> 3. mcfio_block defined in pythia-pgs/libraries/PGS4/src/stdhep-dir/mcfio/src/mcfio_Block.c
>
> Then he mcfio_block function uses the xdr_getpos and xdr_setpos
> functions from the XDR library. These functions are used to get and set
> postion in the output file.
>
> The problem is that these functions operate on 32-bit values and return
> 32-bit values. When the position in file reaches the 4GB limit, the
> 32-bit position overflows and the mcfio/sdthep librarry starts to write
> events in the very beginning of the file and thus corrupts the file
> header.
>
> So, my conclusion is that the mcfio/stdhep library used by the pythia-
> pgs/src/pythia.f program can't work with files larger than 4GB.
>
> --
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> https://bugs.launchpad.net/bugs/1218842
>
> Title:
> STDHEP files larger than 4GB are corrupted
>
> Status in The MadGraph Matrix Element Generator version 5:
> Confirmed
>
> Bug description:
> I've just tested several STDHEP files produced by MG+HERWIG6.
>
> I've tested 50MB, 3.3GB and 4.0GB files.
>
> The 50MB and 3.3GB files can be read without any problem.
>
> The 4.0GB file can't be read.
>
> In the 4.0GB file, already the 2nd block has a block ID number equal
> 2. Normally, it should be 4 (Event Header). The following blocks have
> completely wrong block ID numbers. So, I'd say that it's corrupted
> from the very beginning.
>
> In some cases, adding the following compilation flag helps:
>
> -D_FILE_OFFSET_BITS=64
>
> Normally, the STDHEP library and maybe the PYTHIA and HERWIG
> interfaces should be compiled with this flag.
>
> If you can tell me where to put this flag, I can redo the test.
>
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