C/C++ Examples

Basic C Measurement

Given algorithm.c:

#include <stdio.h>
#include <math.h>

double compute(int n) {
    double sum = 0.0;
    for (int i = 0; i < n; i++)
        sum += sin(i) * cos(i);
    return sum;
}

int main() {
    double result = compute(10000000);
    printf("Result: %f\n", result);
    return 0;
}

Measure energy:

# Coarse: total program energy
codegreen measure c algorithm.c --

# Fine: per-function breakdown
codegreen measure c algorithm.c -g fine

CodeGreen automatically compiles with -O2 and links against libcodegreen-nemb.so.

C++ Measurement

Given nbody.cpp:

codegreen measure cpp nbody.cpp -- 5000
codegreen measure cpp nbody.cpp -g fine --export-plot energy.html -- 5000

How It Works for C/C++

1. Tree-sitter parses the source and identifies function definitions
2. Checkpoint calls are injected at function enter/exit points
3. The instrumented source is compiled with gcc/g++, linking -lcodegreen-nemb -lpthread
4. The compiled binary runs with LD_LIBRARY_PATH set to find libcodegreen-nemb.so
5. Results are collected via the same NEMB backend as Python

Notes

• C++ class bodies are not instrumented (executable statements cannot be placed there)
• Compilation flags: -O2 by default for realistic energy measurement
• The -lpthread flag is required for the NEMB background polling thread