Hello, I have been doing rust for quite a while and i do not have cpp background. I am using the below code for taking input from terminal. What is the best method to take such large input multiple time, also i know only little cpp and do not know how cpp program is taking less time. Input format:…

As a summary of the optimisations we've used: Lock stdin at the start of the process so we don't need to re-lock it on every read Use a buffered reader so we read more input less frequently (Edit: this actually isn't needed because std::io::StdinLock is already buffered and implements BufRead) Reu…

Use stdin().lock() to avoid locking on every read call. You can also make BufReader with a larger buffer. I think 4KB is the default one. let _ = … collect::<Vec<usize>>(); is a total waste. You're allocating memory and dropping it. Use for_each if you want to iterate, but I don't get what the co…

Actually here is the scenario: The above program just reads input and count the number of time it stays in while loop. Just tried locking the stdin() use std::io::{stdin, BufRead, BufReader}; fn main() { let s = stdin(); let mut buf = BufReader::new(s.lock()).lines(); let mut case = …

Try this: use std::io::{stdin, BufRead, BufReader}; fn main() { let s = stdin(); let mut buf = BufReader::new(s.lock()).lines(); let mut case = buf.next().unwrap().unwrap().parse::<usize>().unwrap(); let mut c = 0; while case > 0 { let input = buf.next().unwrap().unwrap…

This would be an equivalent program which only uses the one buffer (adapted to run on the playground). use anyhow::{Context, Error}; use std::io::{self, BufRead, BufReader, Read}; fn count_lines<R: Read>(reader: R) -> Result<(), Error> { let mut reader = BufReader::new(reader); let mut lin…

.lines() will generate a sequence of Strings, each allocated on the heap. You can avoid this by re-using a String like let mut input_line = String::new(); loop { input_line.clear(); match buf.read_line(&mut input_line) { Ok(0) => break, // quit the loop, EO…

Hello, I think now this code is performing better than cpp code, here is the performance for your version of code $ time bash v_rust.sh 10566000 real 0m0.777s user 0m0.764s sys 0m0.060s Thank you very much

You are welcome. I think @Michael-F-Bryan and @qaopm solution/idea should make it even faster.

Hello, I changed the syntax and preserve your method and found it to be better than cpp version. also i love to see some advance version of my program by using anyhow crate. Thank you very much. use std::io::{stdin, BufRead, BufReader}; fn main() { let s = stdin(); let mut reader = BufRea…

std::io::stdin() already is buffered. Re-buffering it only increase the memcpy calls. stdio.rs - source Source of the Rust file `library/std/src/io/stdio.rs`. Edit: this behavior is documented. stdin in std::io - Rust Constructs a new handle to…

That's a good point. It looks like the StdinLock we get when locking stdin also implements BufRead, so we can drop the intermediate BufReader and just call locked_stdin.read_line() directly. That should cut the number of copies in half.

Correct way for taking large input from keyboard

help

Hyeonu February 8, 2021, 3:31pm 11

std::io::stdin() already is buffered. Re-buffering it only increase the memcpy calls.

Edit: this behavior is documented.

Topic		Replies	Views
Code review: a simple input scanner for stdio and file help	1	1180	December 3, 2018
Rust IO reading numbers from stdin	3	190	October 9, 2025
Reading 2 numbers from command line	15	5032	August 5, 2019
Reason for wrongness of Code Jam submission help	6	499	June 7, 2022
Reading stdin line by line selectively help	4	2330	September 16, 2019

Correct way for taking large input from keyboard

Related topics