Re: [Haskell-cafe] Is the #functional programming paradigm antithetical to efficient strings? #Haskell

rust (no need for array but anyway) [bmaxa@manjaro rust]$ time ./append 10000000 took 0.064016791 110000000 took 0.13466229 real 0m0.204s user 0m0.167s sys 0m0.033s haskell (your fastest version) [bmaxa@manjaro rust]$ time ./concat "Done" real 0m0.224s user 0m0.220s sys 0m0.000s c++ (no array) [bmaxa@manjaro rust]$ time ./a.out real 0m0.115s user 0m0.100s sys 0m0.013s rust: use std::time::*; fn main() { let mut arr=Vec::new(); arr.reserve(10_000_000); let start = Instant::now(); for _ in 0 .. 10_000_000 { arr.push("hello world"); } let end = start.elapsed(); let diff = (end.as_secs()*1000000000 + end.subsec_nanos() as u64) as f64/1000000000.; println!("{} took {}",arr.len(),diff); let mut str = String::new(); str.reserve(110_000_000); let start = Instant::now(); for i in arr { str .push_str(i); } let end = start.elapsed(); let diff = (end.as_secs()*1000000000 + end.subsec_nanos() as u64) as f64/1000000000.; println!("{} took {}",str.len(),diff); } c++: #include #include <string> int main() { std::string tmp; tmp.reserve(110000000); for (int i=0;i<10000000;i++) { tmp += "hello world"; } } Model name: Intel(R) Core(TM) i3-5005U CPU @ 2.00GHz On 07/12/2016 05:36 AM, William Yager wrote:

You picked the single slowest way to do it. Please see https://gist.github.com/wyager/df063ad4edd9a9c8b0ab762c91a79894

All times are on my Intel Atom Macbook. Compiled with -O3, no other options.

Using Lazy Bytestrings (either through the Builder interface or plain old concatenation) is about 7-7.5 times faster than string concatenation so on your computer it should take about 0.12 seconds. In other words, faster than C.

This is my usual experience with lazy bytestrings; due to their optimization for cache size, they are extremely fast with almost no effort. They often out-perform "fast" array operations in C due to fusion and cache coherency.

I will note that if you want to do exactly what C does (often with only slightly different assembly output), you can often achieve this with unboxed vectors (mutable or immutable, depending on your application).

--Will

On Mon, Jul 11, 2016 at 10:24 PM, Richard A. O'Keefe mailto:ok@cs.otago.ac.nz> wrote:

Making a list of "Hello world" 10,000,000 times and then concatenating that list to produce a single String took 0.87 seconds (start program to end program) in Haskell.

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