How to Achieve Optimal File Writing Performance in C ?

How to Enhance File Writing Performance in C

When writing voluminous data to a binary file, optimizing performance is crucial. Here's how to enhance your writing speed:

Utilizing FILE* for Direct File Handling:

In the example code, the use of FILE* allows direct file access, bypassing intermediate layers and reducing overhead. This approach yields significant performance gains, as observed in the original question.

Code Optimization for FILE* Usage:

#include <stdio.h><br>const unsigned long long size = 8ULL<em>1024ULL</em>1024ULL;<br>unsigned long long a[size];</p>
<p>int main()<br>{</p>
<pre class="brush:php;toolbar:false">FILE* pFile;
pFile = fopen("file.binary", "wb");
for (unsigned long long j = 0; j < 1024; ++j){
    // Some calculations to fill a[]
    fwrite(a, 1, size*sizeof(unsigned long long), pFile);
}
fclose(pFile);
return 0;

}

This optimized code utilizes FILE* directly to write to the binary file, achieving faster writing speeds.

Comparison of Approaches:

Recent measurements indicate that std::fstream offers comparable performance to FILE* for large file writing. Here's a comparison of different approaches:

#include <fstream></p><h1>include <chrono></h1><h1>include <vector></h1><h1>include <cstdint></h1><h1>include <numeric></h1><h1>include <random></h1><h1>include <algorithm></h1><h1>include <iostream></h1><h1>include <cassert></h1><p>long long option_1(std::size_t bytes)<br>{</p><pre class="brush:php;toolbar:false">// Using std::fstream
std::vector<uint64_t> data = GenerateData(bytes);
auto startTime = std::chrono::high_resolution_clock::now();
auto myfile = std::fstream("file.binary", std::ios::out | std::ios::binary);
myfile.write((char*)&amp;data[0], bytes);
myfile.close();
auto endTime = std::chrono::high_resolution_clock::now();
return std::chrono::duration_cast<std::chrono::milliseconds>(endTime - startTime).count();

}

long long option_2(std::size_t bytes)
{

// Using FILE*
std::vector<uint64_t> data = GenerateData(bytes);
auto startTime = std::chrono::high_resolution_clock::now();
FILE* file = fopen("file.binary", "wb");
fwrite(&amp;data[0], 1, bytes, file);
fclose(file);
auto endTime = std::chrono::high_resolution_clock::now();
return std::chrono::duration_cast<std::chrono::milliseconds>(endTime - startTime).count();

}

Measurements show that both option_1 (std::fstream) and option_2 (FILE*) achieve comparable performance for large file writing.

Conclusion:

For writing large buffers to a binary file in C , both FILE* and std::fstream offer high performance. The choice between the two depends on specific requirements and preferences.

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