qprof

The qprof idea came just after the implementation of the quantum wave equation solver using QatHS, when I reached the optimisation step. Once again the issue was the lack of proper tooling around quantum computing frameworks: I wanted to optimise my implementation, but no tool I was aware of was capable of analysing the quantum circuits I generated and to give me the numbers I want.

The target of this project was to produce a gprof-compatible tool: a program that would analyse quantum circuits and output a summary in the exact same format as gprof.

The constraint on the output format (that should be exactly the same as gprof) was motivated by several points:

1. gprof is nearly 40 years old and is still recognised as one of the standard tools to profile code nowadays. As such, I came to the conclusion that its output format should be the result of many years of polishing and is probably a good starting point.
2. There exist a plethora of tools that plug themselves to gprof post-processing its output. I was mostly looking at the excellent gprof2dot tool that generates a dot file from gprof output. Having an output format compatible with gprof made the usage of all these tools possible and easy.

This project has already been tested on a big implementation involving a lot of nested calls: QatHS. The results are already quite nice as you can see on the following call graphs, generated with qprof, gprof2dot and Graphviz' dot tool using quantum circuits from QatHS.

I ended up reworking a little bit the implementation, taking out of qprof the circuit-wrapper code that was abstracting away the framework the circuit was written in to let qprof ingest a large variety of circuits. The new library doing that is called qcw (which stands for Quantum Circuit Wrapper) and is open-source and available on PyPI with plugins for qiskit, openqasm2 and myqlm.