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I then changed the "run_exe" value from "${EXEROOT}/acme.exe" to "pgdbg gdb ${EXEROOT}/acme.exe" to have it run the debugger in env_mach_specific.xml
EXEROOT
On Titan, the EXEROOT is important because while the executable may normally live in NFS file space, if the executable is an argument to a debugger, it must then live in Lustre space. The EXEROOT variable in CIME is currently defaulting to: $CIME_OUTPUT_ROOT/$CASE/bld, which is good because it means that one can change the location of the executable by specifying --output-root in the ./create_newcase command, which makes things much simpler.
Running Interactively
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qsub -I -A stf006 -lwalltime=01:00:00,nodes=1 -q debugThen, inside the job,
source .env_mach_specific.sh
./case.submit --no-batch