Editing Portal:HPC - High Performance Computing (section)

=== SHMEM, OpenSHMEM, and PGAS-style thinking ===

In HPC, “shmem” can mean more than local SysV shared memory. It can also refer to SHMEM-style or OpenSHMEM-style programming models used in distributed-memory supercomputing.

OpenSHMEM is a Partitioned Global Address Space, or PGAS, style programming model. NVIDIA’s HPC-X documentation describes SHMEM routines as providing low-latency, high-bandwidth communication for highly parallel scalable programs and notes that SHMEM can be used alone or in combination with MPI.<ref>NVIDIA HPC-X Documentation, “PGAS Shared Memory Access Overview,” https://docs.nvidia.com/networking/display/HPCXv215/PGAS%2BShared%2BMemory%2BAccess%2BOverview, accessed July 3, 2026.</ref>

The key idea is that each processing element has local memory, but parts of memory can be accessed in a global, one-sided communication style. This is different from ordinary local shared memory and different from classic two-sided MPI send/receive messaging.

Perl does not have a widely used modern OpenSHMEM ecosystem comparable to C, C++, or Fortran OpenSHMEM codes. However, Perl can still interact with SHMEM-based workflows by:

* generating configuration and launch scripts;
* wrapping compiled OpenSHMEM programs;
* parsing their output;
* managing test cases;
* coordinating benchmarking;
* using FFI or XS for specialized bindings where needed.

The important historical point is that Perl can participate around these programming models even when it is not the language in which the core parallel kernel is written.