Efficiency Comparison Between fstream and C-Style File Read/Write methods (such as fread and fwrite)

 

In order to explore the efficiency of reading and writing files in the C ++ style fstream and C style (such as fread and fwrite), I made two special experiments.

 

My machine is Windows XP, Visual Studio 2008

 

1. Test File writing speed

 

 

Program Design Idea: Write test_size characters into files in two ways and record the time consumption in two ways.

 

 

Lab code:

 

Void test_write () <br/>{< br/> const int test_size = 10000000; <br/> const char * c_plus_write_file = "H: // c_plus_write_file.txt "; <br/> const char * c_write_file = "H: // c_write_file.txt"; </P> <p> cout <"test size:" <test_size <Endl; <br/> // C ++ style Writing File <br/> ofstream of (c_plus_write_file); <br/> assert (of); <br/> time_t start, end; <br/> Start = clock (); <br/> for (INT I = 0; I <test_size; ++ I) <br/>{< br/> char TMP [1]; <br/> TMP [0] = char (I ); <br/> of <TMP [0]; <br/>}< br/> end = clock (); <br/>. close (); <br/> cout <"C ++ style:" <End-start <"Ms" <Endl; <br/> // C style Writing File <br/> file * fp = fopen (c_write_file, "W"); <br/> Start = clock (); <br/> for (INT I = 0; I <test_size; ++ I) <br/>{< br/> char TMP [1]; <br/> TMP [0] = char (I); <br/> fwrite (TMP, 1, 1, FP ); <br/>}< br/> end = clock (); <br/> fclose (FP); <br/> cout <"C style: "<End-start <" Ms "<Endl; <br/> cin. get (); <br/>}< br/> 

 

Experiment results:

Figure 1

Figure 2

Figure 3

 

** As shown in figures 1, 2, and 3, the <operator of ofstream consumes nearly three times the time of fwrite ().

 

 

Changed the code of <to: Of. Write (TMP, 1 );
Result:

 

 

Lab code:

 

Void test_write () <br/>{< br/> const int test_size = 1000000; <br/> const char * c_plus_write_file = "H: // c_plus_write_file.txt "; <br/> const char * c_write_file = "H: // c_write_file.txt"; </P> <p> cout <"test size:" <test_size <Endl; <br/> // C ++ style Writing File <br/> ofstream of (c_plus_write_file); <br/> assert (of); <br/> time_t start, end; <br/> Start = clock (); <br/> for (INT I = 0; I <test_size; ++ I) <br/>{< br/> char TMP [1]; <br/> TMP [0] = char (I); <br/>. write (TMP, 1); <br/>}< br/> end = clock (); <br/>. close (); <br/> cout <"C ++ style:" <End-start <"Ms" <Endl; <br/> // C style Writing File <br/> file * fp = fopen (c_write_file, "W"); <br/> Start = clock (); <br/> for (INT I = 0; I <test_size; ++ I) <br/>{< br/> char TMP [1]; <br/> TMP [0] = char (I); <br/> fwrite (TMP, 1, 1, FP ); <br/>}< br/> end = clock (); <br/> fclose (FP); <br/> cout <"C style: "<End-start <" Ms "<Endl; <br/> cin. get (); <br/>}< br/> 

Experiment results:

 

Figure 4

Figure 5

Figure 6

 

 

Comparison between figure 4 and figure 1, Figure 5 and figure 2, figure 6 and Figure 3 shows that the <operator does not have ofstream. write (), fast, but the two are still not fwrite () fast

 

Conclusion: Efficiency fwrite ()> ofstream. Operator <()> ofstream. Write ()

 

 

 

 

3. The following is a comparison of read files:

 

Program Design Idea: Use two methods to read a text of nearly MB and record the time.

 

Lab code:

Void test_read () <br/>{< br/> const char * read_file = "H: // read4.txt"; <br/> const int buf_size = 1024; <br/> char Buf [buf_size]; <br/> // C ++ style Writing File <br/> ifstream ifs (read_file, IOS: Binary ); <br/> assert (IFS); <br/> time_t start, end; <br/> Start = clock (); <br/> while (! IFS. EOF () <br/>{< br/> ifs. read (BUF, buf_size); <br/>}< br/> end = clock (); <br/> ifs. close (); <br/> cout <"C ++ style:" <End-start <"Ms" <Endl; <br/> // C style Writing File <br/> file * fp = fopen (read_file, "rb"); <br/> Start = clock (); <br/> int Len = 0; <br/> DO <br/> {<br/> Len = fread (BUF, 1, buf_size, FP ); <br/> // cout <Len <Endl; <br/>} while (Len! = 0); <br/> end = clock (); <br/> fclose (FP); <br/> cout <"C style: "<End-start <" Ms "<Endl; <br/> cin. get (); <br/>}< br/> 

 

Experiment results:

Figure 7

 

Conclusion: to read a 100 M file, fread () is nearly ten times more efficient than ifstream. Read! (This conclusion is amazing !)