Re: fgets() vs std::getline() performance

"crhras" <>
16 Sep 2006 07:55:28 -0400
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"crhras" <> wrote in message

Wow ! I just used two different file IO methods and the performance
difference was huge. Is there something that I am doing wrong? or is
fgets() just that much faster than getline()?

Here's the code I used :

// -----------------
std::string line;
std::ifstream in(filename.c_str());

while (std::getline(in, line,'\n'))

// ---------------------------
FILE * fp;
fp = fopen(filename.c_str(), "r");

while (fgets(line, 512, fp) != NULL)

Thank you for the responses. I went back to the drawing board using
your suggestions. Some of the results are in this post and others will
be posted under the specific newsgroup response which I was testing.

First off, the data file used contains 3.5 million text records of
varying lengths terminated by '\n'.

I reran the tests with some timers to tell exactly how long each case is
taking. I ran each test twice in sequence to make sure that caching was
not responsible for the time difference.

// Test 1
  while (std::getline(in, line,'\n')) { }
// Test 2
  while (fgets(cline, 512, fp) != NULL) { }

Results :
Test 1 has taken 203 seconds.
Test 2 has taken 5 seconds.
Test 1 has taken 201 seconds.
Test 2 has taken 4 seconds.

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