发送字节数到标准输出C / C ++最好的方法 [英] C/C++ best way to send a number of bytes to stdout

问题描述

我的概要分析程序和打印功能是服用大量的时间来执行。如何我可以发送原始的字节直接输出到标准输出，而不是使用FWRITE，并使其更快（需要发送的所有9bytes在打印（），同时向标准输出）？

Profiling my program and the function print is taking a lot of time to perform. How can I send "raw" byte output directly to stdout instead of using fwrite, and making it faster (need to send all 9bytes in the print() at the same time to the stdout) ?

void print(){
    unsigned char temp[9];

    temp[0] = matrix[0][0];
    temp[1] = matrix[0][1];
    temp[2] = matrix[0][2];
    temp[3] = matrix[1][0];
    temp[4] = matrix[1][1];
    temp[5] = matrix[1][2];
    temp[6] = matrix[2][0];
    temp[7] = matrix[2][1];
    temp[8] = matrix[2][2];

    fwrite(temp,1,9,stdout);

}

矩阵全局定义为一个无符号字符矩阵[3] [3];

Matrix is defined globally to be a unsigned char matrix[3][3];

推荐答案

IO是不是一种廉价的操作。这是，事实上，一个阻止运行，这意味着操作系统可以preempt你的过程，当你调用写来让更多的CPU-绑定进程运行，你写来完成操作的IO设备之前。

IO is not an inexpensive operation. It is, in fact, a blocking operation, meaning that the OS can preempt your process when you call write to allow more CPU-bound processes to run, before the IO device you're writing to completes the operation.

您可以使用（如果你在* nix机器上开发）唯一较低水平的功能，是使用原始的写功能，但即使如此，你的表现会不会是速度远远超过现在。简单地说：IO是昂贵的。

The only lower level function you can use (if you're developing on a *nix machine), is to use the raw write function, but even then your performance will not be that much faster than it is now. Simply put: IO is expensive.

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