Re: Performance of fread

[Quentin Spencer]

Sascha Berkenkamp wrote:

> Hi,
>
> I would like to know some things about the speed of the fread function.
> In my scenary I'll get about  1000 pictures of one CCD camera. I have 
> to know the data from one pixel about the 1000 pictures. So in my 
> first step I sort the pictures new. So at the result I'll get all 
> informations about the pixel in one file (in my case the 
> pixels-informations of one column of the CCD array in one file).
>
> The second step is to open all the files and read the pixels in order 
> to do some FFT and filtering. I have to read about 800 files (each as 
> about 578 information of the pixels). In the end I do about 400.000 ffts.
> But I think that the fread (and the speed of the disk) function is the 
> least link.
> Is there any chance to make the fread faster, or is it better to do 
> all the task in C?


fread is already written in C, so I don't know how you're going to speed 
it up by rewriting it. Disk speed could be part of the problem, but you 
really haven't provided very much information here. If you really want 
to know what is make this slow, you need to do some measurements using 
functions like tic and toc. If you can provide some data on how much 
time each step is taking, then we can possibly be more helpful.

-Quentin



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