(work in progress - ideas welcome!)

What is my Debugger

On Linux, this is most likely to be gdb (now that Intel have dropped idb).

Serial Debugging

1. compile with -g (and usually with -O0 to turn off any optimisations)
2. start the debugger for the given executable, e.g. gdb ./a.out
3. within the debugger you can either run or if you wish to pass arguments you use run arg1 arg2 for example
4. if there's a memory issue, then gdb will halt at the bad line. if there's no issues it will continue until completion or until you CNTL-C and enter a gdb command

Debugging OpenMP

1. compile with -g (and usually with -O0 to turn off any optimisations) and the OpenMP compilation flag e.g. -fopenmp
2. set the number of OpenMP threads e.g. export OMP_NUM_THREADS=2
3. start the debugger for the given executable, e.g. gdb ./a.out
4. within the debugger you can either run or if you wish to pass arguments you use run arg1 arg2 for example
5. if there's a memory issue, then gdb will halt at the bad line on the first thread that has a problem. if there's no issues it will continue until completion or until you CNTL-C and enter a gdb command

Debugging MPI

1. compile with -g (and usually with -O0 to turn off any optimisations) for your favored MPI installation e.g. mpiicc -g -O0
2. we need to use mpirun -np N (for N processes) and for this to launch a terminal, e.g. xterm in which we can then start the debugger for the given executable. That is we will have a command line akin to
   mpirun -np N xterm -e gdb ./a.out
3. within the debugger in each terminal you can either run or if you wish to pass arguments you use run arg1 arg2 for example
4. if there's a memory issue, then gdb will halt at the bad line on the first process that has a problem. if there's no issues it will continue until completion or until you CNTL-C and enter a gdb command

Useful gdb commands

quit the debugger (may be needed on each thread and each process)