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Code Coverage

Overview

This example demonstrates code coverage analysis by providing two functionally identical code paths - run_real() and run_fake() - that can be switched at runtime via the CODE_COVERAGE_USE_FAKE environment variable. Both functions perform multi-threaded Fibonacci computation with atomic result accumulation. By toggling which path executes, you can test profiler and coverage tool capabilities to detect exercised vs. unexercised code branches and measure instrumentation completeness across alternate execution paths.

Source Files

  • code-coverage.cpp - Defines fib() (recursive Fibonacci), run_real() and run_fake() (identical Fibonacci computation with atomic accumulation), and a function-pointer-based dispatch selected by environment variable.
  • code-coverage.py - Python companion script for coverage analysis.

Prerequisites

  • CMake 3.25+
  • C++ compiler with pthreads support

Building

Standalone build:

cmake -B <build_dir> -S <project_root>/examples/code-coverage
cmake --build <build_dir>

As part of the examples suite:

cmake -B <build_dir> -S <project_root>/examples/
cmake --build <build_dir> --target code-coverage

Running

# Default: run_real path, fib(10), min(16, ncpus) threads, 5000 iterations
./code-coverage

# Use alternate code path
CODE_COVERAGE_USE_FAKE=1 ./code-coverage

# Custom: fib(12), 4 threads, 2000 iterations
./code-coverage 12 4 2000

Arguments:

Position Description Default
1 Fibonacci number to compute 10
2 Number of threads min(16, hardware concurrency)
3 Number of iterations per thread 5000

Environment:

Variable Description
CODE_COVERAGE_USE_FAKE If set, switches to run_fake() code path

Profiling with rocprofiler-systems

# Profile the default path
rocprof-sys-run -- ./code-coverage 10 4 2000

# Profile the alternate path
rocprof-sys-run -e CODE_COVERAGE_USE_FAKE=1 -- ./code-coverage 10 4 2000
Variable Value Purpose
ROCPROFSYS_TRACE true Generate Perfetto trace
ROCPROFSYS_PROFILE true Generate call-stack profile showing exercised functions
ROCPROFSYS_USE_SAMPLING ON Enable sampling for coverage correlation