dm1sh/polynomial_interpolation
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Switched to "recursive" polynomial siplification

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Dmitriy Shishkov 2021-10-31 16:26:27 +03:00
parent 8555f1e30e
commit 5311f70746
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GPG Key ID: 14358F96FCDD8060
2 changed files with 16 additions and 57 deletions
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68
main.c
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@ -38,66 +38,26 @@ double *div_diff_es(double *x, double *y, unsigned int n)
Coeficients of simplified polynomial computation Coeficients of simplified polynomial computation
*/ */
void simplify_polynomial(double *res, double *rev_el_coef, double *x, unsigned int n) void simplify_polynomial(double *res, double *el_coef, double *x, unsigned int n)
{ {
double *tmp_polynomial = (double *)malloc(sizeof(double) * n);
tmp_polynomial[0] = 1;
for (int i = 0; i < n; i++) for (int i = 0; i < n; i++)
if (rev_el_coef[i]) if (el_coef[i])
{
if (i > 0)
mult_by_root(tmp_polynomial, x[i - 1], i - 1);
for (int j = 0; j <= i; j++) for (int j = 0; j <= i; j++)
res[i - j] += (j % 2 ? -1 : 1) * rev_el_coef[i] * compute_sum_of_multiplications_of_k(x, j, i); res[j] += el_coef[i] * tmp_polynomial[j];
}
} }
double compute_sum_of_multiplications_of_k(double *arr, unsigned int k, unsigned int n) void mult_by_root(double *res, double root, unsigned int step)
{ {
if (k == 0) for (int j = step + 1; j >= 0; j--)
return 1; res[j] = (j ? res[j - 1] : 0) - (root * res[j]);
if (k == 1 && n == 1)
return arr[0];
unsigned int *selected = (unsigned int *)malloc(sizeof(unsigned int) * k); // Indexes of selected for multiplication elements
int i = 0, // index of `arr` array
j = 0; // index of `selected` array
double sum = 0;
while (j >= 0)
{
if (i <= (n + (j - k)))
{
selected[j] = i;
if (j == k - 1)
{
sum += mult_by_indexes(arr, selected, k);
i++;
}
else
{
i = selected[j] + 1;
j++;
}
}
else
{
j--;
if (j >= 0)
i = selected[j] + 1;
}
}
free(selected);
return sum;
}
double mult_by_indexes(double *arr, unsigned int *indexes, unsigned int size)
{
double res = 1;
for (int i = 0; i < size; i++)
res *= arr[indexes[i]];
return res;
} }
/* /*

5
polynominal_interpolation.h
View File

@ -30,8 +30,7 @@ void print_poly(double *coef, unsigned int n);
Coeficients of simplified polynomial computation Coeficients of simplified polynomial computation
*/ */
void simplify_polynomial(double *res, double *rev_el_coef, double *x, unsigned int n); void simplify_polynomial(double *res, double *el_coef, double *x, unsigned int n);
double compute_sum_of_multiplications_of_k(double *x, unsigned int k, unsigned int n); void mult_by_root(double *res, double root, unsigned int step);
double mult_by_indexes(double *arr, unsigned int *indexes, unsigned int size);
#endif #endif