make cin cout faster
To make cin
and cout
faster in C++, you can use the following techniques:
1. Disable synchronization with C I/O functions:
By default, cin
and cout
are synchronized with the C I/O functions (stdio
). This means that when you read from or write to cin
or cout
, the corresponding C I/O functions are also called, which can slow down the process. You can disable this synchronization to make cin
and cout
faster by adding the following lines of code at the beginning of your program:
std::ios::sync_with_stdio(false);
std::cin.tie(nullptr);
The std::ios::sync_with_stdio(false)
line disables the synchronization between iostream
and stdio
, and std::cin.tie(nullptr)
unties cin
from cout
, which further improves the performance.
2. Use a larger buffer size:
By default, cin
and cout
use a small buffer size for input and output operations. You can increase the buffer size to reduce the number of system calls, which can improve the performance. You can do this by calling the rdbuf()
function on cin
and cout
and setting a larger buffer size. For example:
std::cout.rdbuf(std::cout.rdbuf()->pubsetbuf(nullptr, 0));
std::cin.rdbuf(std::cin.rdbuf()->pubsetbuf(nullptr, 0));
The pubsetbuf
function sets the buffer to nullptr
and the size to 0
, which lets the stream library choose an appropriate buffer size.
3. Avoid unnecessary calls to endl
:
The endl
manipulator in C++ is equivalent to '\n'
and also flushes the output buffer. Calling endl
frequently can slow down the output operation. Instead, you can use '\n'
to insert a newline character without flushing the buffer, unless you explicitly need to flush the buffer.
By applying these techniques, you can make cin
and cout
faster in your C++ programs. Remember to test the performance gain after making these changes, as the actual impact may vary depending on the specific program and system configuration.