> Hi,
> 
> Is it possible to have a view of a float64 array that is itself float32?
> So that:
> 
>>>> A = np.arange(5, dtype='d')
>>>> A.view(dtype='f')
> 
> would return a size 5 float32 array looking at A's data?

I think not. The memory layout of a 32-bit IEEE float is not a subset of that 
of a 64-bit float -- see e.g. the first table in:
http://steve.hollasch.net/cgindex/coding/ieeefloat.html

This would work for int8/int16 or other int types (so long as the number 
doesn't exceed the range of the smaller type), but AFAIK not floats.

Note how the subset relationship works for the int8/int16 case, but not 
float32/float64:

str(numpy.array(100,dtype=numpy.int8).data)
'd'

str(numpy.array(100,dtype=numpy.int16).data)
'd\x00'

str(numpy.array(-100,dtype=numpy.int16).data)
'\x9c\xff'

str(numpy.array(-100,dtype=numpy.int8).data)
'\x9c'

str(numpy.array(100,dtype=numpy.float32).data)
'\x00\x00\xc8B'

str(numpy.array(100,dtype=numpy.float64).data)
'\x00\x00\x00\x00\x00\x00Y@'


Zach



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