[Numpy-discussion] type of matrixmultiply result

[Todd Miller]

On Thu, 2004-06-24 at 06:14, Curzio Basso wrote:
> Hi.
> 
> I noticed that when multiplying two matrices of type Float32, the result 
> is Float64:
> 
> -----------------------------------------
> In [103]: a=NA.ones((2,2), NA.Float32)
> 
> In [104]: b=NA.ones((2,2), NA.Float32)
> 
> In [105]: c=NA.matrixmultiply(a,b)
> 
> In [106]: c.type()
> Out[106]: Float64
> -----------------------------------------
> 
> Since the matrix I'm going to multiply in practice are quite big, I'd 
> like to do the operation in Float32. Otherwise this is what I get:
> 
> Traceback (most recent call last):
>    File "/home/basso/work/python/port/apps/pca-heads.py", line 141, in ?
>      pc = NA.array(NA.matrixmultiply(cent, c), NA.Float32)
>    File "/home/basso/usr//lib/python/numarray/numarraycore.py", line 
> 1150, in dot    return ufunc.innerproduct(array1, _gen.swapaxes(array2, 
> -1, -2))
>    File "/home/basso/usr//lib/python/numarray/ufunc.py", line 2047, in 
> innerproduct
>      r = a.__class__(shape=adots+bdots, type=rtype)
> MemoryError
> 
> Any suggestion (apart from doing the operation one column at a time)?
> 

I modified dot() and innerproduct() this morning to return Float32 and
Complex32 for like inputs.  This is in CVS now.  numarray-1.0 is
dragging out,  but will nevertheless be released relatively soon.

I'm curious about what your array dimensions are.  When I implemented
matrixmuliply for numarray,  I was operating under the assumption that
no one would be multiplying truly huge arrays because it's an O(N^3)
algorithm.

Regards,
Todd

> thanks
> 
> 
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-- 
Todd Miller <jmiller at stsci.edu>