I have the following matrix 4x4:
1 2 3 4
5 6 7 8
9 10 11 12
13 14 15 16
and I want extract and store (in some news variables) the four following submatrix 2x2:
[1 2
5 6]
[3 4
7 8]
[9 10
13 14]
[11 12
15 16]
It's like the "Rect" ( http://docs.opencv.org/java/org/opencv/core/Rect.html ) function of openCV, but I don'want to use OpenCV.
I have to use a parallelizing compiler and so I would like to do the extraction of the submatrix with a famous loop transformation present in literature: "loop tiling" (also knows as "loop blocking" or "loop unroll and jam" or "loop stripmine and interchange"). - ( http://en.wikipedia.org/wiki/Loop_tiling )
Is it possible?
Is it possible?
Of course …
int n = 4;
int matrix[4][4] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16};
int submatrixes[n/2*n/2][2][2];
int i, j, x, y, z;
for (z = i = 0; i < n; i += 2)
for (j = 0; j < n; j += 2, ++z)
for (x = 0; x < 2; x++)
for (y = 0; y < 2; y++)
submatrixes[z][x][y] = matrix[i+x][j+y];
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