Caliper is a library to integrate performance profiling capabilities into
applications. To use Caliper, developers mark code regions of interest using
Caliper's annotation API. Applications can then enable performance profiling at
runtime with Caliper's configuration API. Alternatively, you can configure
Caliper through environment variables or config files.

Caliper can be used for lightweight always-on profiling or advanced performance
engineering use cases, such as tracing, monitoring, and auto-tuning. It is
primarily aimed at HPC applications, but works for any C/C++/Fortran program on
Unix/Linux.