Last active
June 1, 2018 14:49
-
-
Save milleniumbug/d2d0d3ecfd96c5c36a2d7d92b464ab47 to your computer and use it in GitHub Desktop.
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
#include <random> | |
#include <iostream> | |
int main() | |
{ | |
std::random_device rd; | |
std::uniform_int_distribution<> dist(-1000000, 1000000); | |
for(int i = 0; i < 10000000; ++i) | |
std::cout << dist(rd) << "\n"; | |
} |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
#include <cstdio> | |
#include <chrono> | |
#include <iostream> | |
int main() { | |
using std::chrono::steady_clock; | |
using std::chrono::duration_cast; | |
using std::chrono::milliseconds; | |
auto start = steady_clock::now(); | |
int i; | |
for (auto _ = 0; _ < 10'000'000; ++_) { | |
std::cin >> i; | |
} | |
auto end = steady_clock::now(); | |
std::cout << "cin: " << duration_cast<milliseconds>(end - start).count() << '\n'; | |
} |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
#include <cstdio> | |
#include <chrono> | |
#include <iostream> | |
int main() { | |
using std::chrono::steady_clock; | |
using std::chrono::duration_cast; | |
using std::chrono::milliseconds; | |
auto start = steady_clock::now(); | |
int i; | |
for (auto _ = 0; _ < 10'000'000; ++_) { | |
scanf("%d", &i); | |
} | |
auto end = steady_clock::now(); | |
std::cout << "scanf: " << duration_cast<milliseconds>(end - start).count() << '\n'; | |
} |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
➜ ~ g++ -v | |
Using built-in specs. | |
COLLECT_GCC=g++ | |
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-redhat-linux/6.3.1/lto-wrapper | |
Target: x86_64-redhat-linux | |
Configured with: ../configure --enable-bootstrap --enable-languages=c,c++,objc,obj-c++,fortran,ada,go,lto --prefix=/usr --mandir=/usr/share/man --infodir=/usr/share/info --with-bugurl=http://bugzilla.redhat.com/bugzilla --enable-shared --enable-threads=posix --enable-checking=release --enable-multilib --with-system-zlib --enable-__cxa_atexit --disable-libunwind-exceptions --enable-gnu-unique-object --enable-linker-build-id --with-linker-hash-style=gnu --enable-plugin --enable-initfini-array --disable-libgcj --with-isl --enable-libmpx --enable-gnu-indirect-function --with-tune=generic --with-arch_32=i686 --build=x86_64-redhat-linux | |
Thread model: posix | |
gcc version 6.3.1 20161221 (Red Hat 6.3.1-1) (GCC) | |
➜ ~ g++ -O2 -std=c++14 cin.cpp -Wall -Wextra -pedantic -o cin.o | |
➜ ~ g++ -O2 -std=c++14 scanf.cpp -Wall -Wextra -pedantic -o scanf.o | |
➜ ~ for i in `seq 1 10`; do ./cin.o < nums; ./scanf.o < nums; done | |
cin: 4040 | |
scanf: 1575 | |
cin: 4293 | |
scanf: 1561 | |
cin: 4037 | |
scanf: 1567 | |
cin: 4078 | |
scanf: 1528 | |
cin: 4012 | |
scanf: 1575 | |
cin: 4074 | |
scanf: 1552 | |
cin: 4038 | |
scanf: 1534 | |
cin: 4044 | |
scanf: 1535 | |
cin: 4118 | |
scanf: 1533 | |
cin: 4002 | |
scanf: 1548 |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
(with std::cin.sync_with_stdio(false); ) | |
➜ ~ for i in `seq 1 10`; do ./cin.o < nums; ./scanf.o < nums; done | |
cin: 1435 | |
scanf: 1586 | |
cin: 1412 | |
scanf: 1526 | |
cin: 1457 | |
scanf: 1574 | |
cin: 1433 | |
scanf: 1527 | |
cin: 1439 | |
scanf: 1591 | |
cin: 1464 | |
scanf: 1586 | |
cin: 1434 | |
scanf: 1571 | |
cin: 1401 | |
scanf: 1610 | |
cin: 1435 | |
scanf: 1567 | |
cin: 1414 | |
scanf: 1604 | |
(with std::cin.sync_with_stdio(false); and std::cin.tie(nullptr); ) | |
cin: 1367 | |
scanf: 1584 | |
cin: 1329 | |
scanf: 1551 | |
cin: 1329 | |
scanf: 1570 | |
cin: 1340 | |
scanf: 1587 | |
cin: 1315 | |
scanf: 1585 | |
cin: 1382 | |
scanf: 1539 | |
cin: 1386 | |
scanf: 1624 | |
cin: 1343 | |
scanf: 1551 | |
cin: 1354 | |
scanf: 1587 | |
cin: 1314 | |
scanf: 1608 |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
I lost the actual run times, but the overall results were something along: | |
MSVC has scanf being 3 times faster than cin with unmodified code | |
and 2 and 1/3 times faster than cin with std::cin.sync_with_stdio(false); and std::cin.tie(nullptr); | |
(release mode, x64) | |
MinGW has scanf being 13/9 times faster than cin with unmodified code | |
MinGW has scanf being 18/5 times slower than cin with std::cin.sync_with_stdio(false); and std::cin.tie(nullptr); |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment