Reading a large binary file

I want to load a 8 GB binary data file into Matlab. My computer has 24 GB of RAM. It runs out of memory, despite me closing literally everything besides Matlab, and I don't understand why. The file should not take more than its size, right?

Code for loading is simply:

fd = fopen(['data.bin'], 'r');
data = fread(fd, 'int16');
fclose(fd);

Answer 1

[James Tursa]

Try

data = fread(fd, '*int16');

When you use 'int16' for the type to read, MATLAB reads as int16 and then converts to double (four times the memory). When you use '*int16', MATLAB keeps the type as int16. E.g.,

% Create a small sample file
fid = fopen('junk.bin','wb');
fwrite(fid,int16(4),'int16');
fclose(fid);
% read it with 'int16'
fid = fopen('junk.bin','rb');
x = fread(fid,'int16')

x = 4

class(x) % double, not what you wanted

ans = 'double'

% read it with '*int16'
frewind(fid);
x = fread(fid,'*int16')

x = int16 4

class(x) % int16, this is what you wanted

ans = 'int16'

fclose(fid);

[Dominik Rhiem]

Positive side effect: This is extremely fast.