Comparing ways to concatenate strings in Rust 1.61 nightly (1.58 stable)

Intro

There are many ways to turn a &str into a String in Rust and therefore many ways to concatenate two &strs.

Here I benchmark several different ways to concatenate the strings "2014-11-28", "T" and "12:00:09Z" into "2014-11-28T12:00:09Z".

Thanks to all the comments on and discussion on reddit where I posted these originally only 7 benchmarks. Some go into the details of what is going on in the background of these operations.

How to run?

benchmarks: cargo +nightly bench
tests: cargo +nightly test --benches

Results (on my machine)

$ cargo +nightly bench

running 46 tests
test array_concat_test ... ignored
test array_join_long_test ... ignored
test array_join_test ... ignored
test collect_from_array_to_string_test ... ignored
test collect_from_vec_to_string_test ... ignored
test concat_in_place_macro_test ... ignored
test concat_string_macro_test ... ignored
test concat_strs_macro_test ... ignored
test format_macro_implicit_args_test ... ignored
test format_macro_test ... ignored
test from_bytes_test ... ignored
test joinery_test ... ignored
test mut_string_push_str_test ... ignored
test mut_string_push_string_test ... ignored
test mut_string_with_capacity_push_str_char_test ... ignored
test mut_string_with_capacity_push_str_test ... ignored
test mut_string_with_too_little_capacity_push_str_test ... ignored
test mut_string_with_too_much_capacity_push_str_test ... ignored
test string_concat_macro_test ... ignored
test string_from_all_test ... ignored
test string_from_plus_op_test ... ignored
test to_owned_plus_op_test ... ignored
test to_string_plus_op_test ... ignored
test array_concat                                 ... bench:          24 ns/iter (+/- 0)
test array_join                                   ... bench:          22 ns/iter (+/- 0)
test array_join_long                              ... bench:          24 ns/iter (+/- 0)
test collect_from_array_to_string                 ... bench:          30 ns/iter (+/- 0)
test collect_from_vec_to_string                   ... bench:          34 ns/iter (+/- 0)
test concat_in_place_macro                        ... bench:          14 ns/iter (+/- 0)
test concat_string_macro                          ... bench:          10 ns/iter (+/- 0)
test concat_strs_macro                            ... bench:          10 ns/iter (+/- 0)
test format_macro                                 ... bench:          52 ns/iter (+/- 0)
test format_macro_implicit_args                   ... bench:          53 ns/iter (+/- 0)
test from_bytes                                   ... bench:           0 ns/iter (+/- 0)
test joinery                                      ... bench:          46 ns/iter (+/- 0)
test mut_string_push_str                          ... bench:          24 ns/iter (+/- 0)
test mut_string_push_string                       ... bench:          68 ns/iter (+/- 1)
test mut_string_with_capacity_push_str            ... bench:          10 ns/iter (+/- 1)
test mut_string_with_capacity_push_str_char       ... bench:          10 ns/iter (+/- 0)
test mut_string_with_too_little_capacity_push_str ... bench:          39 ns/iter (+/- 0)
test mut_string_with_too_much_capacity_push_str   ... bench:          19 ns/iter (+/- 10)
test string_concat_macro                          ... bench:          10 ns/iter (+/- 0)
test string_from_all                              ... bench:          43 ns/iter (+/- 1)
test string_from_plus_op                          ... bench:          27 ns/iter (+/- 0)
test to_owned_plus_op                             ... bench:          29 ns/iter (+/- 0)
test to_string_plus_op                            ... bench:          27 ns/iter (+/- 0)

test result: ok. 0 passed; 0 failed; 23 ignored; 23 measured; 0 filtered out; finished in 33.39s

The same results rearranged fastest to slowest

0 ns/iter (+/- 0)         from_bytes
10 ns/iter (+/- 0)        concat_string_macro
10 ns/iter (+/- 0)        concat_strs_macro
10 ns/iter (+/- 0)        mut_string_with_capacity_push_str_char
10 ns/iter (+/- 0)        string_concat_macro
10 ns/iter (+/- 1)        mut_string_with_capacity_push_str
14 ns/iter (+/- 0)        concat_in_place_macro
19 ns/iter (+/- 10)       mut_string_with_too_much_capacity_push_str
22 ns/iter (+/- 0)        array_join
24 ns/iter (+/- 0)        array_concat
24 ns/iter (+/- 0)        array_join_long
24 ns/iter (+/- 0)        mut_string_push_str
27 ns/iter (+/- 0)        string_from_plus_op
27 ns/iter (+/- 0)        to_string_plus_op
29 ns/iter (+/- 0)        to_owned_plus_op
30 ns/iter (+/- 0)        collect_from_array_to_string
34 ns/iter (+/- 0)        collect_from_vec_to_string
39 ns/iter (+/- 0)        mut_string_with_too_little_capacity_push_str
43 ns/iter (+/- 1)        string_from_all
46 ns/iter (+/- 0)        joinery
52 ns/iter (+/- 0)        format_macro
53 ns/iter (+/- 0)        format_macro_implicit_args
68 ns/iter (+/- 1)        mut_string_push_string

Examples explained

`array_concat()`

let datetime = &[DATE, T, TIME].concat();

`array_join()`

let datetime = &[DATE, TIME].join(T);

`array_join_long()`

let datetime = &[DATE, T, TIME].join("");

`collect_from_array_to_string()`

let list = [DATE, T, TIME];
let datetime: String = list.iter().map(|x| *x).collect();

`collect_from_vec_to_string()`

let list = vec![DATE, T, TIME];
let datetime: String = list.iter().map(|x| *x).collect();

`format_macro()`

let datetime = &format!("{}{}{}", DATE, T, TIME);

`format_macro_implicit_args()`

let datetime = &format!("{DATE}{T}{TIME}");

`from_bytes()` ⚠️ don't actually do this

use std::ffi::OsStr;
use std::os::unix::ffi::OsStrExt;
use std::slice;

let bytes = unsafe { slice::from_raw_parts(DATE.as_ptr(), 20) };

let datetime = OsStr::from_bytes(bytes);

`mut_string_push_str()`

let mut datetime = String::new();
datetime.push_str(DATE);
datetime.push_str(T);
datetime.push_str(TIME);

`mut_string_push_string()`

let mut datetime = Vec::<String>::new();
datetime.push(String::from(DATE));
datetime.push(String::from(T));
datetime.push(String::from(TIME));
let datetime = datetime.join("");

`mut_string_with_capacity_push_str()`

let mut datetime = String::with_capacity(20);
datetime.push_str(DATE);
datetime.push_str(T);
datetime.push_str(TIME);

`mut_string_with_capacity_push_str_char()`

let mut datetime = String::with_capacity(20);
datetime.push_str(DATE);
datetime.push('T');
datetime.push_str(TIME);

`mut_string_with_too_little_capacity_push_str()`

let mut datetime = String::with_capacity(2);
datetime.push_str(DATE);
datetime.push_str(T);
datetime.push_str(TIME);

`mut_string_with_too_much_capacity_push_str()`

let mut datetime = String::with_capacity(200);
datetime.push_str(DATE);
datetime.push_str(T);
datetime.push_str(TIME);

`string_from_all()`

let datetime = &(String::from(DATE) + &String::from(T) + &String::from(TIME));

`string_from_plus_op()`

let datetime = &(String::from(DATE) + T + TIME);

`to_owned_plus_op()`

let datetime = &(DATE.to_owned() + T + TIME);

`to_string_plus_op()`

let datetime = &(DATE.to_string() + T + TIME);

Additional macro benches

`concat_string_macro`

Rank: #1 @10ns
Crate: https://crates.io/crates/concat-string

#[macro_use(concat_string)]
extern crate concat_string;
let datetime = concat_string!(DATE, T, TIME);

`concat_strs_macro`

Rank: #1 @10ns
Crate: https://crates.io/crates/concat_strs

Unfortunately, this macro breaks RustAnalyzer.

#[macro_use(concat_strs)]
extern crate concat_strs;
let datetime = &concat_strs!(DATE, T, TIME);

`string_concat_macro`

Rank: #1 @10ns
Crate: https://crates.io/crates/string_concat

#[macro_use]
extern crate string_concat;
let datetime = &string_concat::string_concat!(DATE, T, TIME);

`concat_in_place_macro`

Rank: #2 @14ns
Crate: https://crates.io/crates/concat-in-place

let datetime = concat_in_place::strcat!(&mut url, DATE T TIME);

`joinery`

Rank: #12 @46ns
Crate: https://crates.io/crates/joinery

use joinery::prelude::*;
let vec = vec![DATE, T, TIME];
let datetime = &vec.iter().join_concat().to_string();

hoodie/concatenation_benchmarks-rs

hoodie

Reviews

Repository Details

Comparing ways to concatenate strings in Rust 1.61 nightly (1.58 stable)

Intro

How to run?

Results (on my machine)

The same results rearranged fastest to slowest

Examples explained

`array_concat()`

`array_join()`

`array_join_long()`

`collect_from_array_to_string()`

`collect_from_vec_to_string()`

`format_macro()`

`format_macro_implicit_args()`

`from_bytes()` ⚠️ don't actually do this

`mut_string_push_str()`

`mut_string_push_string()`

`mut_string_with_capacity_push_str()`

`mut_string_with_capacity_push_str_char()`

`mut_string_with_too_little_capacity_push_str()`

`mut_string_with_too_much_capacity_push_str()`

`string_from_all()`

`string_from_plus_op()`

`to_owned_plus_op()`

`to_string_plus_op()`

Additional macro benches

`concat_string_macro`

`concat_strs_macro`

`string_concat_macro`

`concat_in_place_macro`

`joinery`

More Repositories

hoodie/concatenation_benchmarks-rs

hoodie

Reviews

Repository Details

Comparing ways to concatenate strings in Rust 1.61 nightly (1.58 stable)

Intro

How to run?

Results (on my machine)

The same results rearranged fastest to slowest

Examples explained

array_concat()

array_join()

array_join_long()

collect_from_array_to_string()

collect_from_vec_to_string()

format_macro()

format_macro_implicit_args()

from_bytes() ⚠️ don't actually do this

mut_string_push_str()

mut_string_push_string()

mut_string_with_capacity_push_str()

mut_string_with_capacity_push_str_char()

mut_string_with_too_little_capacity_push_str()

mut_string_with_too_much_capacity_push_str()

string_from_all()

string_from_plus_op()

to_owned_plus_op()

to_string_plus_op()

Additional macro benches

concat_string_macro

concat_strs_macro

string_concat_macro

concat_in_place_macro

joinery

More Repositories

`array_concat()`

`array_join()`

`array_join_long()`

`collect_from_array_to_string()`

`collect_from_vec_to_string()`

`format_macro()`

`format_macro_implicit_args()`

`from_bytes()` ⚠️ don't actually do this

`mut_string_push_str()`

`mut_string_push_string()`

`mut_string_with_capacity_push_str()`

`mut_string_with_capacity_push_str_char()`

`mut_string_with_too_little_capacity_push_str()`

`mut_string_with_too_much_capacity_push_str()`

`string_from_all()`

`string_from_plus_op()`

`to_owned_plus_op()`

`to_string_plus_op()`

`concat_string_macro`

`concat_strs_macro`

`string_concat_macro`

`concat_in_place_macro`

`joinery`