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| ▲ | hatthew 3 hours ago | parent [-] | | The program is a useless toy that nobody would write and expect to be performant in real life. I can write an optimized version of the algorithm that prints the exact same output (barring edge cases) without looping. With this new algorithm (really just a single expression), the C program is 500x faster than before and the python script is 5000x faster than before. So python is only 10x slower than C in this example (and I'd imagine that this is measuring more overhead and less arithmetic). Presumably the C compiler has a relative advantage at optimizing the looped algorithm vs the arithmetic algorithm. How much? Is C 100x faster than python, or was the compiler able to get closer to the non-looping algorithm than python? How close? Is it something about the arithmetic or the looping that's natively faster in C? What part of it was optimized by the compiler? Since nobody does large loops in python, would python be more comparable if we introduced a C-backed library like numpy? What other objects do you think we should bash this apple with? | | |
| ▲ | Dylan16807 3 hours ago | parent [-] | | Do you think a slightly more complex piece of math that can't be replaced with an equation would have significantly different performance from the benchmark? I don't. So the simple math just makes things easier, it doesn't harm results. Your suggestion to skip the math entirely is the apple-smash. > Since nobody does large loops in python Oh I doubt that. Numpy would be fine as a different entry. | | |
| ▲ | hatthew 2 hours ago | parent [-] | | I don't know whether or not a more complex piece of math would change the outcome, so I would err on the side of not making assumptions until I had done more benchmarks and investigated the inner workings more. You probably know more about C than I do and might be able to make that assumption more confidently, but I think most people know less than either of us, and will read too much into a single statistic without context. Nobody who cares about performance enough to look at a benchmark like this would do large loops in pure python. | | |
| ▲ | Dylan16807 2 hours ago | parent [-] | | > Nobody who cares about performance enough to look at a benchmark like this would do large loops in pure python. Because they already know it would be very slow, and putting specific numbers on that is helpful for them and for non-veterans too. Even with some wiggle room for "microbenchmarks are weird". | | |
| ▲ | hatthew an hour ago | parent [-] | | I already know that python is generally slower than C. This microbenchmark tells me that python is 100x slower than C, but only in these specific circumstances that wouldn't happen in the real world, but may or may not be similar enough to the real world to infer that C could be 10^(2±1) faster, but only for a small portion of someone's program, and only if they don't use one of the libraries that they probably do use. Personally, I find it misleading for the results of a benchmark to be posted when it's not made clear up front what the benchmark is measuring. At minimum I'd want a disclaimer that mentions at least one of the first two points mentioned in the top comment https://news.ycombinator.com/item?id=42250205 |
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