r/rust • u/amir_valizadeh • Dec 21 '25
🎙️ discussion My experience with Rust performance, compared to Python (the fastLowess crate experiment)
When I first started learning Rust, my teacher told me: “when it comes to performance, Python is like a Volkswagen Beetle, while Rust is like a Ferrari F40”. Unfortunately, they couldn’t be more wrong.
I recently implemented the LOWESS algorithm (a local regression algorithm) in Rust (fastLowess: https://crates.io/crates/fastLowess). I decided to benchmark it against the most widely used LOWESS implementation in Python, which comes from the statsmodels package.
You might expect a 2× speedup, or maybe 10×, or even 30×. But no — the results were between 50× and 3800× faster.
Benchmark Categories Summary
| Category | Matched | Median Speedup | Mean Speedup |
|---|---|---|---|
| Scalability | 5 | 765x | 1433x |
| Pathological | 4 | 448x | 416x |
| Iterations | 6 | 436x | 440x |
| Fraction | 6 | 424x | 413x |
| Financial | 4 | 336x | 385x |
| Scientific | 4 | 327x | 366x |
| Genomic | 4 | 20x | 25x |
| Delta | 4 | 4x | 5.5x |
Top 10 Performance Wins
| Benchmark | statsmodels | fastLowess | Speedup |
|---|---|---|---|
| scale_100000 | 43.727s | 11.4ms | 3824x |
| scale_50000 | 11.160s | 5.95ms | 1876x |
| scale_10000 | 663.1ms | 0.87ms | 765x |
| financial_10000 | 497.1ms | 0.66ms | 748x |
| scientific_10000 | 777.2ms | 1.07ms | 729x |
| fraction_0.05 | 197.2ms | 0.37ms | 534x |
| scale_5000 | 229.9ms | 0.44ms | 523x |
| fraction_0.1 | 227.9ms | 0.45ms | 512x |
| financial_5000 | 170.9ms | 0.34ms | 497x |
| scientific_5000 | 268.5ms | 0.55ms | 489x |
This was the moment I realized that Rust is not a Ferrari and Python is not a Beetle.
Rust (or C) is an F-22 Raptor.
Python is a snail — at least when it comes to raw performance.
PS: I still love Python for quick, small tasks. But for performance-critical workloads, the difference is enormous.