What is the best way to parse a large floating point file stored in ASCII?
What would be the fastest way to do it? I remember someone telling me using ifstream was bad, because it worked on a small number of bytes, and it would be better to just read the file into memory first. Is that true?
Edit: I am running on Windows, and the file format is for a point cloud that is stored in rows like x y z r g b. I am attempting to read them into arrays. Also, the files are around 20 MB each, but I have around 10 GB worth of them.
Second edit: I am going to have to load the files to display every time I want to do a visualization, so it would be nice to have it as fast as possible, but honestly, if ifstream preforms reasonably, I wouldn’t mind sticking with readable code. It’s running quite slow right now, but that might be more of a hardware I/O limitation than anything I can do in software, I just wanted to confirm.
I think your first concern should be how large the floating point numbers are. Are they float or can there be double data too? The traditional (C) way would be to use fscanf with the format specifier for a float and afaik it is rather fast. The iostreams do add a small overhead in terms of parsing the data, but that is rather negligible. For the sake of brevity I would suggest you use iostreams (not to mention the usual stream features that you’d get with it).
Also, I think it will really help the community if you could add the relevant numbers along with your question, like for e.g., how large a file are you trying to parse ? Is this a small memory footprint environment (like an embedded system).