Dear list,
I'm trying to read a section of a large 4-d chunk array into memory and am
getting some strange behaviour.
The array is a set up as:
/realizations (CArray(3, 1978, 1556, 288), shuffle, zlib(1)) ''
atom := Float32Atom(shape=(), dflt=0.0)
maindim := 0
flavor := 'numpy'
byteorder := 'little'
chunkshape := (1, 1978, 1556, 1)
so overall dimensions of (3, 1978, 1556, 288) made up of chunks of (1, 1978,
1556, 1).
Reading in a 2-d block (corresponding to a single chunk)...
f_chunk = hr.realizations[0,:,:,0]
...takes under a second.
Reading in a 3-d block of width=2 across the first dimension....
f_chunk = hr.realizations[0:2:1,:,:,0]
...takes about a second:
So far so good, but reading in a 3-d block of width=2 across the fourth
dimension....
f_chunk = hr.realizations[0,:,:, 0:2:1]
...suddenly takes nearer 45 minutes!
I'd be very grateful if anyone could explain why the latter operation is
requiring this much time - clearly something is going on in pytables that I
don't currently understand...
Thanks in advance,
Pete
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