linear combinations in python/numpy
- by nmaxwell
greetings,
I'm not sure if this is a dumb question or not.
Lets say I have 3 numpy arrays, A1,A2,A3, and 3 floats, c1,c2,c3
and I'd like to evaluate B = A1*c1+ A2*c2+ A3*c3
will numpy compute this as for example,
E1 = A1*c1
E2 = A2*c2
E3 = A3*c3
D1 = E1+E2
B = D1+E3
or is it more clever than that? In c++ I had a neat way to abstract this kind of operation.
I defined series of general 'LC' template functions, LC for linear combination like:
template<class T,class D>
void LC( T & R,
T & L0,D C0,
T & L1,D C1,
T & L2,D C2)
{
R = L0*C0
+L1*C1
+L2*C2;
}
and then specialized this for various types,
so for instance, for an array the code looked like
for (int i=0; i<L0.length; i++)
R.array[i] =
L0.array[i]*C0 +
L1.array[i]*C1 +
L2.array[i]*C2;
thus avoiding having to create new intermediate arrays.
This may look messy but it worked really well.
I could do something similar in python, but I'm not sure if its nescesary.
Thanks in advance for any insight.
-nick
