Reducing Computation Time

Question

Dejan Cvijanovic 2012-4-26

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https://ww2.mathworks.cn/matlabcentral/answers/36697-reducing-computation-time

Hey I have somewhat tricky task of reducing computation time for one line of code in my professor's project. Is there any way to reduce the following code so that it computes at a faster rate (maybe 0.01s), right now the time to beat is 0.08s. The code is as follows:

(32 bit IEEE demultiplexed)

x = hex2float( dec2hex( fread(fid, 1, 'ubit32', 0, 'ieee-be') ))

Basicslly looking for quicker way to convert the binary file to float. If you're not sure, I'm open to specifics suggestions. Also, would it be better if I wrote a code like this in C first and then let matlab read from there? Thank you.

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Answer 1

Jan 2012-4-26

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https://ww2.mathworks.cn/matlabcentral/answers/36697-reducing-computation-time#answer_45883

在 MATLAB Online 中打开

d = fread(fid, 1, 'uint32', 'ieee-be');
x = hex2float(sprintf('%x', d));

I do not have hex2float. Could you provide some example data? I assume typecast(uint32(d), 'single') will help also, if the format of fread is set accordingly. But without hex2float I cannot test this.

See also: http://stackoverflow.com/questions/5232726/32-bit-hex-to-32-bit-floating-point-ieee-754-conversion-in-matlab

Anyhow, 0.08 sec sounds extremely slow. I assume this is cause by the rest of the code.

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Dejan Cvijanovic 2012-4-26

*produce float numbers eventually

Jan 2012-4-30

Thanks, Walter. I cannot find it in the FEX: http://www.mathworks.com/matlabcentral/fileexchange/?sort=date_desc_updated&term=hex2float

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Answer 2

Walter Roberson 2012-4-26

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https://ww2.mathworks.cn/matlabcentral/answers/36697-reducing-computation-time#answer_45884

在 MATLAB Online 中打开

Is there a reason you are not just using

x = fread(fid, 1, '*float32', 0, 'ieee-be')

Also if you are doing a lot of calculations, it is almost always faster to use fread() to read a number of items at once. (If you stick with going through hex, then dec2hex() can be used on arrays.)