File get contents vs fread performance

New replies are no longer allowed. Am I correct? Quote from the manual: In my opinion you should use fread only if you are working with streams and you have functionality based on that the code has fopen of stuff and you already have the resource.

What do you need to achieve? On my i machine with Ubuntu Yes, mmap gained a nearly 4x speedup! I have verified on two other machines, they also reported at least 3x speedup. So I have a lot of experience with mmap and unfortunately how fast it works is highly dependent on the OS and what bells or whistles you have installed. Years ago Digital Unix had a well deserved reputation for being the fastest mmap. It was and no doubt still is just blazing fast.

In fact Unix in general tends to have high quality fast mmap implementations. When I moved to the Linux world it was like being kicked by a horse. Memory mapping was either poorly implemented or just plain missing! It has slowly improved over the years but still leaves a lot to be desired on many versions of Linux. Memory mapping on windows has generally been okay, but there again they have been working on it and it has improved over time. Your email address will not be published.

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Save my name, email, and website in this browser for the next time I comment. You may subscribe to this blog by email. Skip to content My home page My papers My software. It is as simple as it gets. The standard C library also offers a higher level fread function.

Unlike the read function, you can set a buffer size. Buffers can be good or bad. On the one hand, they reduce the number of disk accesses. On the other hand, they introduce an intermediate step between the disk and you data. That is, they may cause the data to be copied needlessly. Buffers usually makes software faster because copying data in memory is much faster than reading it from disk.

It is very similar to fread, but with a more object-oriented flavor. Finally, you can use memory mapping. Instead of reading blocks of data, you map the content of the file to a pointer and the operating system is responsible with filling in the data. It has the reputation to be very fast because the data on disk can be mapped directly to memory without any undue copying.

However, in my experience, it is also less stable: you are unlikely to cause a bus error with fread or ifstream, but the slightest mistake with memory mapping and your program can crash. Memory mapping is not beneficial: method millions of int. Published by. Here are the results: fread That is correct, the little program reports the speed, so higher numbers are better. Unfortunately, IO is difficult to benchmark reliably.

Rogers Thanks. Sign in Join Now. New Post. Follow Post Reply. You need the handle provided by fopen for many operations like fgetcsv. Another advantage of fread is that you can read just a said amount of bytes from a line - you don't have to read the full file at once. Jerry Stuckle. Like almost anything else in programming, "it depends". But it can also be slower - because it reads the entire file into memory at one time.

If you're not having performance problems, I'd say don't worry about it.