Re: Matrix Dot Product

*To*: mathgroup at smc.vnet.net*Subject*: [mg52182] Re: [mg52159] Matrix Dot Product*From*: Hugh Walker <hwalker at gvtc.com>*Date*: Sun, 14 Nov 2004 04:30:20 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

On Saturday, November 13, 2004, at 03:40 AM, MacDonald, Calum ((MAT)) wrote: > Hi > > I was wondering if someone could please help me with a command for > calculating the dot product of two (NxN) matrices. > > For example, for two (2x2) matrices, A and B, we define the dot > product > as: > > A(1,1)*B(1,1) + A(2,1)*B(2,1) + A(1,2)*B(1,2) + A(2,2)*B(2,2) > > i.e. we multiply corresponding entries of the matrices and sum these > values. > > It is easy to write this in a loop but for large matrices the > calculation is rather slow. > > Is there a Mathematica function that I can call that will allow me to > do > this faster? > > Thanks > > Calum Let aMat and bMat each be nXn matrices. One way to compute your "dot prod', surely faster than looping, is (a//Flatten).(b//Flatten) ========== Hugh Walker Gnarly Oaks