[Numpy-discussion] Efficient ?axpy operation without copy (B += a*A)

Michael McNeil Forbes mforbes@physics.ubc...
Tue Jun 23 13:19:48 CDT 2009


Hi,

Is there a way of performing vectorized ?axpy (daxpy) operations  
without making copies or dropping into C?

i.e: I want to do

big = (10000,5000)
A = np.ones(big,dtype=float)
B = np.ones(big,dtype=float)
a = 1.5
B += a*A

without making any copies?

(I know I could go

A *= a
B += A
A /= a

but that is not so efficient either).

There are exposed blas daxpy operations in scipy, but in the version I  
have (EPD), these also seem to make copies (though recent version seem  
to be fixed by looking at the source.)

Thanks,
Michael.


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