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Commented coefficients functions

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Dmitriy Shishkov 2021-10-31 16:52:34 +03:00
parent c8682c7563
commit c0c5e219ea
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1 changed files with 18 additions and 13 deletions
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main.c
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@ -38,26 +38,31 @@ double *div_diff_es(double *x, double *y, unsigned int n)
Coeficients of simplified polynomial computation
*/
/* Simplifies Newton polynomial with `el_coef` array of divided differences,
and `x` as array of x coordinates of dots,
and `n` is number of elements of this sum */
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;
double *tmp_polynomial // Temporary array for storage of coefficients of multiplication of (x-x_i) polynomial
= (double *)malloc(sizeof(double) * n);
tmp_polynomial[0] = 1; // Set polynomial to 1 to start multiplication with it
for (int i = 0; i < n; i++)
if (el_coef[i])
{
if (i > 0)
mult_by_root(tmp_polynomial, x[i - 1], i - 1);
for (int i = 0; i < n; i++) // For each elemnt of sum
{
if (i > 0) // Start multiplication from second element of sum
mult_by_root(tmp_polynomial, x[i - 1], i - 1);
for (int j = 0; j <= i; j++)
res[j] += el_coef[i] * tmp_polynomial[j];
}
for (int j = 0; j <= i; j++) // For each cumputed coefficient of i'th polynomial of sum
res[j] += el_coef[i] * tmp_polynomial[j]; // Add it, multiplied with divided difference, to sum
}
}
void mult_by_root(double *res, double root, unsigned int step)
/* `res` is an array of coefficients of polynomial which is multiplied with (x - `root`) polynomial
`power` is the power of `res` polynomial */
void mult_by_root(double *res, double root, unsigned int power)
{
for (int j = step + 1; j >= 0; j--)
res[j] = (j ? res[j - 1] : 0) - (root * res[j]);
for (int j = power + 1; j >= 0; j--)
res[j] = (j ? res[j - 1] : 0) - (root * res[j]); // coefficient is k_i-1 - root * k_i
}
/*