112 lines
2.1 KiB
C
112 lines
2.1 KiB
C
#include "solve.h"
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#include "io_status.h"
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#include <float.h>
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// c - changes in rows
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int t14_solve(int n, double * restrict A, double * restrict X, int * restrict c)
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{
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for (int k = 0; k < n; ++k) {
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max_t max = { .val = -1.0 };
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#pragma omp parallel for reduction(+:max)
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for (int i = k; i < n; ++i)
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for (int j = k; j < n; ++j)
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{
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double aij = fabs(A[i * n + j]);
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if (aij > max.val) {
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max.val = aij;
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max.i = i;
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max.j = j;
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}
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}
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if (fabs(max.val) < DBL_EPSILON)
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return SINGULAR;
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if (max.i != k)
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{
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#pragma omp simd
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for (int kn = k*n, in = max.i*n; kn < k*(n+1); ++kn, ++in)
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{
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double swap = X[kn];
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X[kn] = X[in];
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X[in] = swap;
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}
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#pragma omp parallel for simd
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for (int kn = k*n+k, in = max.i*n+k; kn < (k+1)*n; ++kn, ++in)
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{
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double swap = X[kn];
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X[kn] = X[in];
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X[in] = swap;
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swap = A[kn];
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A[kn] = A[in];
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A[in] = swap;
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}
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}
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if (max.j != j)
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{
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int swap_temp = c[max.j];
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c[max.j] = k;
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c[k] = swap_temp;
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#pragma omp simd
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for (int in = k * n; in < n; in+=n)
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{
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double swap = A[in + k];
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A[in + k] = A[in + max.j];
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A[in + max.j] = swap;
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}
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}
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gauss_inverse(n, k, A, X);
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}
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}
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void gauss_inverse(const int n, const int k, double * restrict A, double * restrict X)
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{
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const int kn = k*n, const int kk = kn + k;
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const double inv_akk = 1./A[kn + k];
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A[kn + k] = 1.;
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for (int ij = kn; ij < kn+k; ++ij)
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{
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double xij = X[ij];
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if (fabs(xij) > DBL_EPSILON) X[ij] = xij*inv_akk;
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}
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for (int ij = kn + k+1; ij < kn+n; ++ij)
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{
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double aij = A[ij], xij = X[ij];
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if (fabs(aij) > DBL_EPSILON) A[ij] = aij*inv_akk;
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if (fabs(xij) > DBL_EPSILON) X[ij] = xij*inv_akk;
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}
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#pragma omp parallel for
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for (int i = k+1; i < n; ++i)
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{
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const int in = i*n;
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const double aik = A[in + k];
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A[in + k] = 0;
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X[in + k] -= X[kk] * aik;
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#pragma omp simd
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for (int j = 0; j < k; ++j)
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X[in + j] -= X[kn + j] * aik;
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#pragma omp simd
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for (int j = k+1; j < n; ++j)
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{
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A[in + j] -= A[kn + j] * aik;
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X[in + j] -= X[kn + j] * aik;
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}
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}
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}
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void gauss_back_substitution(const int n, double * restrict A, double * restrict X)
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{
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}
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