Using pagemtimes multiplying from left and right side

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Morten Nissov
Morten Nissov el 3 de Mayo de 2021
Respondida: Felipe Padua el 29 de Ag. de 2022
I have a 3D array I need to multiply on left and right sides by a constant 3x3 matrix, take a cholesky decomposition and multiply it by a random vector, I am trying to avoid for loops. The arrays are P 6x6xN and F 3x6. The equivalent for loop multiplication is
for i=1:length(Pf)
w = chol(Fn*Pf(:,:,i)*Fn')*randn(3,1);
out(:,i) = out(:,i) + w;
end

Respuestas (1)

Felipe Padua
Felipe Padua el 29 de Ag. de 2022
You can use pagemtimes to perform both multiplications but, since chol accept only matrices (2D arrays) as arguments, you'll still need a loop. Try the code below:
n = size(Pf, 3);
aux = pagemtimes(Fn, Pf);
aux = pagemtimes(aux, Fn');
for i = 1:n
aux (:,:,i) = chol(aux(:,:,i));
end
aux = pagemtimes(aux, rand(3,1,n));
If you desire retrieve the steps taken, you may avoid overwriting the aux variable renaming the sucessive results as aux1, aux2 etc, or other names of your preference.

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