bilboquet / perf-tests

Currious to see how c++ and rust behave relatively to each other

perf-tests

Currious to see how c++ and rust behave relatively to each other

Tests descriptions

A naïve algorithme that search for the 20001st prime number. Implemented in C,C++ and rust in a way that looks idiomatic…

Building the test binaries

C/C++

cd nth-prime_cpp
make

generates 3 binaries:

• nth_prime_array is a C++ using an array to store the prime numbers
• nth_prime_vector is a C++ using a vector to store the prime numbers
• nth_prime_array_c is a C version using variadic array

Rust

cd nth-prime_rs
cargo build
cargo build --release

generates 2 binaries:

• target/debug/nth_prime with debug info and some code instrumentation
• target/release/nth_prime optimized for runtime

perf results

C/C++

nth-prime_cpp$ hyperfine ./nth_prime_array_c
Benchmark #1: ./nth_prime_array_c
  Time (mean ± σ):     947.5 ms ±   7.3 ms    [User: 938.4 ms, System: 7.5 ms]
  Range (min … max):   940.0 ms … 960.6 ms    10 runs

nth-prime_cpp$ hyperfine ./nth_prime_array
Benchmark #1: ./nth_prime_array
  Time (mean ± σ):     956.8 ms ±  19.9 ms    [User: 951.1 ms, System: 5.8 ms]
  Range (min … max):   941.2 ms … 999.7 ms    10 runs

nth-prime_cpp$ hyperfine ./nth_prime_vector
Benchmark #1: ./nth_prime_vector
  Time (mean ± σ):     966.2 ms ±  30.1 ms    [User: 961.0 ms, System: 5.3 ms]
  Range (min … max):   940.7 ms … 1036.8 ms    10 runs

Rust

nth-prime_rs$ hyperfine target/debug/nth_prime
Benchmark #1: target/debug/nth_prime
  Time (mean ± σ):      9.415 s ±  0.043 s    [User: 9.393 s, System: 0.013 s]
  Range (min … max):    9.367 s …  9.510 s    10 runs

nth-prime_rs$ hyperfine target/release/nth_prime
Benchmark #1: target/release/nth_prime
  Time (mean ± σ):     701.7 ms ±  18.0 ms    [User: 700.3 ms, System: 0.7 ms]
  Range (min … max):   685.3 ms … 744.9 ms    10 runs

Tools version

$ gcc --version
gcc (Ubuntu 8.3.0-6ubuntu1) 8.3.0

$ g++ --version
g++ (Ubuntu 8.3.0-6ubuntu1) 8.3.0

$ rustup --version
rustup 1.19.0 (2af131cf9 2019-09-08)

$ cargo --version
cargo 1.37.0 (9edd08916 2019-08-02)

$ rustc --version
rustc 1.37.0 (eae3437df 2019-08-13)

Conclusion

The first attempt, that triggered the creation of this page, showed that the C++ version with vector was 4 times slower than the one with simple array.

The results were not recorded and can't be reproduced for the moment, in a sense that's a good news because all C/C++ versions have the same performances, but it requires more investigation to understand where the problem was.

On the other side, Rust implementation compiled in release mode outperform all other solutions.

Comments are very welcome (I'm n00b)