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POWhy is this C code faster than this C++ code ? getting biggest line in file
 

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  1. POWhy is this C code faster than this C++ code ? getting biggest line in file
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    <p>I have two versions of a program that does basically the same thing, getting the biggest length of a line in a file, I have a file with about 8 thousand lines, my code in C is a little bit more primitive (of course!) than the code I have in C++. The C programm takes about 2 seconds to run, while the program in C++ takes 10 seconds to run (same file I am testing with for both cases). But why? I was expecting it to take the same amount of time or a little bit more but not 8 seconds slower!</p> <p>my code in C:</p> <pre><code>#include &lt;stdio.h&gt; #include &lt;stdlib.h&gt; #include &lt;string.h&gt; #if _DEBUG #define DEBUG_PATH "../Debug/" #else #define DEBUG_PATH "" #endif const char FILE_NAME[] = DEBUG_PATH "data.noun"; int main() { int sPos = 0; int maxCount = 0; int cPos = 0; int ch; FILE *in_file; in_file = fopen(FILE_NAME, "r"); if (in_file == NULL) { printf("Cannot open %s\n", FILE_NAME); exit(8); } while (1) { ch = fgetc(in_file); if(ch == 0x0A || ch == EOF) // \n or \r or \r\n or end of file { if ((cPos - sPos) &gt; maxCount) maxCount = (cPos - sPos); if(ch == EOF) break; sPos = cPos; } else cPos++; } fclose(in_file); printf("Max line length: %i\n", maxCount); getch(); return (0); } </code></pre> <p>my code in C++:</p> <pre><code>#include &lt;iostream&gt; #include &lt;fstream&gt; #include &lt;stdio.h&gt; #include &lt;string&gt; using namespace std; #ifdef _DEBUG #define FILE_PATH "../Debug/data.noun" #else #define FILE_PATH "data.noun" #endif int main() { string fileName = FILE_PATH; string s = ""; ifstream file; int size = 0; file.open(fileName.c_str()); if(!file) { printf("could not open file!"); return 0; } while(getline(file, s) ) size = (s.length() &gt; size) ? s.length() : size; file.close(); printf("biggest line in file: %i", size); getchar(); return 0; } </code></pre>
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      1. POWhy is this C code faster than this C++ code ? getting biggest line in file
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    1. COThe programs are far from being equivalent. You actually copy the whole line into memory in C++ version. Equivalent C++ version would be C version with `file >> ch;` instead of `ch = fgetc(in_file);`
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      1. POWhy is this C code faster than this C++ code ? getting biggest line in file
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    2. COWhat does getline() in the C++ version do? I've seen ifstream.getline() but not a getline function that takes ifstream...?
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      1. POWhy is this C code faster than this C++ code ? getting biggest line in file
      1. USJoachim Isaksson
    3. COBtw, both 2 and 10 seconds seems very slow for just a few thousand lines. What kind of computer are you using?
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      1. POWhy is this C code faster than this C++ code ? getting biggest line in file
      1. USThomas Padron-McCarthy
 

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