Arm DDT is an advanced debugging tool used for scalar, multi-threaded, and large-scale parallel applications.
In addition to traditional debugging features (setting breakpoints, stepping through code, examining variables), DDT also supports attaching to already-running processes and memory debugging. In-depth details of DDT can be found in the Official DDT User Guide, and instructions for how to use it on OLCF systems can be found on the Forge (DDT/MAP) Software Page. DDT is the OLCF’s recommended debugging software for large parallel applications.


GDB, the GNU Project Debugger, is a command-line debugger useful for traditional debugging and investigating code crashes. GDB lets you debug programs written in Ada, C, C++, Objective-C, Pascal (and many other languages). GDB is available on Summit under all compiler families:

module load gdb

Additional information about GDB usage and OLCF-provided builds can be found on the GDB Software Page.


Valgrind is an instrumentation framework for building dynamic analysis tools. There are Valgrind tools that can automatically detect many memory management and threading bugs, and profile your programs in detail. You can also use Valgrind to build new tools.

The Valgrind distribution currently includes five production-quality tools: a memory error detector, a thread error detector, a cache and branch-prediction profiler, a call-graph generating cache profiler, and a heap profiler. It also includes two experimental tools: a data race detector, and an instant memory leak detector.

The Valgrind tool suite provides a number of debugging and profiling tools. The most popular is Memcheck, a memory checking tool which can detect many common memory errors such as:

  • Touching memory you shouldn’t (eg. overrunning heap block boundaries, or reading/writing freed memory).
  • Using values before they have been initialized.
  • Incorrect freeing of memory, such as double-freeing heap blocks.
  • Memory leaks.

Valgrind is available on Summit under all compiler families:

module load valgrind

Additional information about Valgrind usage and OLCF-provided builds can be found on the Valgrind Software Page.