Multi Dimension Matrix Elements multiplication
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Hello,
I am strugling with some matrix multiplication...
I am having one M: 
matrix and one N: 
matrix with some given elements. Elements of M are given as 
whereas elements of N are given as 
. I wish to obtain maxtrix P: 
whose elements 
, 
and 
. Thus, matrix 
would be in my case.
matrix and one N: matrix with some given elements. Elements of M are given as whereas elements of N are given as . I wish to obtain maxtrix P: whose elements , and . Thus, matrix would be in my case.Does anyone know how to perform this complex operation in the fastest way (without loops)?
Thanks in advance
回答（2 个）
Not completely without loops, but this should be fast enough. You should also be aware that loops can sometimes be the fastest way.
M=rand(3,2);N=rand(2,3,4);
%prime the execution engine to produce a more reliable comparison
timeit(@()option1(M,N));
timeit(@()option1(M,N))
timeit(@()option2(M,N))
isequal(option1(M,N),option2(M,N))
function P=option1(M,N)
P=zeros(size(M,1),size(N,2),size(N,3));
for n=1:size(M,1)
P(n,:,:)=M(n,1)*N(1,:,:)+M(n,2)*N(2,:,:);
end
end
function P=option2(M,N)
P=zeros(size(M,1),size(N,2),size(N,3));
for i=1:size(M,1)
for j=1:size(N,2)
for k=1:size(N,3)
P(i,j,k)=M(i,1)*N(1,j,k)+M(i,2)*N(2,j,k);
end
end
end
end
Steven Lord
2021-2-24
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