77 lines
1.6 KiB
C
77 lines
1.6 KiB
C
#include "solve.h"
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#include <math.h>
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#define eps 1e-17
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int t8_solve(double *a, int m, int n)
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{
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const int BS = 30;
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int max_i = 0, max_j = 0;
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double maximum = 0;
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for (int jj = 0; jj < n; jj += BS)
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for (int j = jj; j < jj + BS && j < n; j++)
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{
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double sum_j = 0;
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for (int ii = 0; ii < m; ii += BS)
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for (int k = ii; k < ii + BS && k < m; k++)
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sum_j += fabs(a[k*n + j]);
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for (int ii = 0; ii < m; ii += BS)
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for (int i = ii; i < ii + BS && i < m; i++)
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{
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double sum_i = 0;
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double aij = fabs(a[i*n + j]);
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sum_j -= aij;
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if (j == 0)
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{
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double num = a[i*n];
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for (int kk = 1; kk < n; kk += BS)
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for (int k = kk; k < kk + BS && k < n; k++)
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sum_i += fabs(a[i*n + k]);
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a[i*n] = copysign(fabs(num) + sum_i, num);
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}
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else
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sum_i = fabs(a[i*n]) - fabs(a[i*n + j]);
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if (((sum_j + sum_i) - maximum) > eps)
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maximum = (sum_j + sum_i), max_i = i, max_j = j;
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sum_j += aij;
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}
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}
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if (max_j != 0)
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for (int ii = 0; ii < m; ii += BS)
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for (int i = ii; i < ii + BS && i < m; i++)
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{
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double orig = a[i*n];
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double num = fabs(orig);
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for (int jj = 1; jj < n; jj += BS)
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for (int j = jj; j < jj + BS && j < n; j++)
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num -= fabs(a[i*n + j]);
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a[i*n] = copysign(num, orig);
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}
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for (int l = max_j+1, del_j = 1; l < max_i*n; l++)
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{
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if (l == ((n * del_j) + max_j))
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del_j++;
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else
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a[l - del_j] = a[l];
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}
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for (int l = (max_i+1)*n, del_j = max_i; l < m*n; l++)
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{
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if (l == ((n * (del_j + 1)) + max_j))
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del_j++;
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else
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a[l - del_j - n] = a[l];
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}
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return max_i * n + max_j;
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}
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