| File sizes and the SAVE command [message #48054] |
Wed, 22 March 2006 01:39 |
Carsten Pathe
Messages: 5
Registered: December 2002
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Junior Member |
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Hi there,
I am wondering about the IDL save command and the disk space of the
created save files.
Just an simple example:
a=intarr(100000)
tmp = size(a)
print, string(format='(f10.3)',(tmp(1)*tmp(2))/(2.^10.))+' kbyte'
;195.313 kbyte
save, a, filename='d:\temp\test\b.dat'
b=fltarr(100000)
tmp = size(b)
print, string(format='(f10.3)',(tmp(1)*tmp(2))/(2.^10.))+' kbyte'
;390.625 kbyte
save, a, filename='d:\temp\test\a.dat'
c=dblarr(100000)
tmp = size(c)
print, string(format='(f10.3)',(tmp(1)*tmp(2))/(2.^10.))+' kbyte'
;488.281 kbyte
save, c, filename='d:\temp\test\c.dat'
When you look at the created files and their sizes, you will see the
following:
a.dat 393 kb
b.dat 393 kb
c.dat 784 kb
If you compare the file sizes to the sizes, the arrays were allocating
in the memory before they were save to disk, you see differences which
will cost you a lot of disk space when saving arrays of several hundred
megabytes.
Does anybody know, why the save command is producing files larger than
they should be?
PS: I know, that I can also use:
openw, 10, 'd:\temp\test\a.dat'
writeu, 10, a
close, 10
But when I want to restore the data, I have to know the structure of the
data to restore - which is not always the case.
Thanks a lot help
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