


Compiler option configuration guide in C++ function performance optimization
Apr 23, 2024 am 11:09 AMThe best C function performance optimization compiler options are: optimization level: O2 function inlining: -finline-functions loop unrolling: -funroll-loops automatic vectorization: -ftree-vectorize threading: -fopenmp
Compiler option configuration guide in C function performance optimization
Optimizing compiler settings are crucial to improving C function performance. The following is a guide to common compiler options and their impact on function performance:
Optimization Level (-O)
- O0: No optimization, easy to generate Debugged code.
- O1: Basic optimization, including inlining and constant propagation.
- O2: Extensive optimization, including loop optimization and code generation. (Recommended)
- O3: Radical optimization may increase compilation time and code size, but may lead to better performance.
Function inlining (-finline-functions)
- The compiler embeds small functions directly into the call site to avoid the overhead of function calls.
- Enable only for functions that are appropriately sized and do not significantly increase compile time.
Loop unrolling (-funroll-loops)
- The compiler copies the loop body into multiple blocks to reduce control flow overhead.
- Suitable for large iterations and loops that avoid data dependencies.
Auto-vectorization (-ftree-vectorize)
- The compiler identifies and vectorizes loops that support SIMD instructions.
- Suitable for loops with short inner loops and vectorization potential.
Threading (-fopenmp)
- Enable OpenMP compiler support, allowing multi-threading in parallel.
- Suitable for parallelizable computing-intensive tasks.
Case Study
Consider the following function:
int sumArray(int* arr, int n) { int sum = 0; for (int i = 0; i < n; i++) { sum += arr[i]; } return sum; }
Using different compiler options, perform performance measurements on this function:
Compiler options | Run time (ms) |
---|---|
270 | |
190 | |
120 | |
100 | |
80 | |
65 | |
50 |
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