Problem 60753. 2x2 binning of a large sparse matrix

Consider the 20000 x 20000 sparse matrix,
A=round(sprand(2e4,2e4,1/1e4*100)*1000);
The task is to divide this matrix into 2x2 tiles and to form the reduced 10000 x 10000 matrix B such that B(i,j) is the sum over the elements of (i,j)-th tile of A. For example,
B(1,1) = A(1,1)+A(2,1)+A(1,2)+A(2,2)
B(2,1) = A(3,1)+A(4,1)+A(3,2)+A(4,2)
etc...
Your solution must execute in less than 0.3 sec.
Solve

Solution Stats

71.43% Correct | 28.57% Incorrect
Last Solution submitted on Oct 30, 2024

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