Improve header isolation and parse time of logger.h by Renaud-K · Pull Request #4445 · NVIDIA/cuda-quantum

Renaud-K · 2026-05-04T17:29:54Z

As we prepare to surface qpu headers in user code, cudaq.h is become significantly slower to parse in a prototyping sandbox. This PR addresses a slowdown introduced by logger.h as can be seen in the profile below.

The compiled code is:

#include <cudaq.h>

int main() {
return 0;
}

The compile time is 3.6s.

time clang++ cudaq_inc.cpp -std=c++20  -I ~/cudaq/cq2/install/cudaq/include
real    0m3.603s

The profile shows logger.h takes 441ms of parse time.

With this patch, the compilation time becomes 2.9s

time clang++ cudaq_inc.cpp -std=c++20  -I ~/cudaq/cq2/install/cudaq/include
real    0m2.936s

The profile show logger.h only taking 7ms.

This is achieved by replacing the std::variant with a FormatArgument which only stores a pointer and an out-of-line appending callback. The callback is instantiated in logger.cpp.

Renaud-K · 2026-05-04T17:30:52Z

/ok to test b2a36a7

Command Bot: Processing...

github-actions · 2026-05-04T18:23:57Z

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copy-pr-bot · 2026-05-04T20:25:54Z

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Renaud-K · 2026-05-04T20:26:37Z

/ok to test ded40b5

Command Bot: Processing...

sacpis

Overall LGTM. Thanks @Renaud-K. Left a few comments.

Signed-off-by: Renaud Kauffmann <rkauffmann@nvidia.com>

Renaud-K · 2026-05-06T02:56:21Z

/ok to test ad44648

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github-actions · 2026-05-06T03:45:08Z

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Renaud-K requested review from 1tnguyen, amccaskey, boschmitt, sacpis and taalexander May 4, 2026 17:29

Renaud-K force-pushed the logger-header branch from b2a36a7 to ded40b5 Compare May 4, 2026 20:25

sacpis approved these changes May 4, 2026

View reviewed changes

Renaud-K added 3 commits May 5, 2026 18:44

Improve header isolation of logger

a973941

Signed-off-by: Renaud Kauffmann <rkauffmann@nvidia.com>

Fix for gcc12

67bb889

Signed-off-by: Renaud Kauffmann <rkauffmann@nvidia.com>

Review feedback

ad44648

Signed-off-by: Renaud Kauffmann <rkauffmann@nvidia.com>

Renaud-K force-pushed the logger-header branch from ded40b5 to ad44648 Compare May 5, 2026 23:47

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