How can I do faster a loop using the GPU? (GPU: RTX 3070)

n=700;

A=rand(n,n);

%%

Ms=gpuArray(M);

As=gpuArray(A);

% First questions: this loop takes to much time. How can I do this loop using the cores available in the GPU

tic

for i=1:100;

AA(:,:,i)=As; %this is just an example, in practice, As is different for each i of the loop

MM(:,:,i)=Ms; %Ms is the same for all the indexes i.

end

toc

%I m using this array to make 2 multiplications and a pointwise produt

% This are the multiplications

AGpage=gpuArray(AA);

Fs=gpuArray(fftshift(dftmtx(m)));%

Gs=gpuArray(fftshift(dftmtx(n)));

CG=pagefun(@mtimes,AGpage,Fs);

Hs=pagefun(@mtimes,Gs,CG);

% what I need next is this result: sum(Ms.*Hs,[2 1]);

%But, I use a reshape to use all the cores in the pointwise multiplication

Ms2=gpuArray(MM);

MMT=reshape(Ms2,l,l,49*100);

ST=reshape(Hs,l,l,49*100);

for iter=1:30

aG2=sum(MMT.*ST,[2 1]);

%%

% I need to go back to recover the sum of the pointwise multiplication sum(Ms.*Hs,[2 1]);

%First questions: But now, again this loop is too slow

for index=1:100

tramo=aG2((index-1)*49+1:49*index);

aG3(index)=sum(tramo);

end

%how can I do faster a loop using the GPU?