70 lines
1 KiB
C
70 lines
1 KiB
C
#include "solve.h"
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#include <math.h>
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#include <float.h>
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#include <stdbool.h>
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#include <stdint.h>
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#include <string.h>
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int t1_solve (
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double (*f) (double),
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double a, double b,
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double eps, int m, double *x
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) {
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int it = 0;
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uint64_t bits;
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double c = DBL_MAX, y, y_a = f(a), y_b = f(b);
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bool sgn_a, sgn_b, sgn_c;
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memcpy(&bits, &y_a, sizeof(bits));
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sgn_a = (bits >> 63) & 1;
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memcpy(&bits, &y_b, sizeof(bits));
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sgn_b = (bits >> 63) & 1;
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if (fabs(y_a) - eps < DBL_EPSILON)
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{
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*x = a;
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return 1;
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} if (fabs(y_b) - eps < DBL_EPSILON)
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{
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*x = b;
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return 1;
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}
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if (sgn_a == sgn_b)
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{
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*x = DBL_MAX;
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return -1;
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}
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for (it = 1; it <= m; ++it)
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{
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c = (a + b) * 0.5;
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y = f(c);
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memcpy(&bits, &y, sizeof(bits));
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sgn_c = (bits >> 63) & 1;
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if (fabs(y) - eps < DBL_EPSILON)
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break;
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else if ((fabs(c - a) < DBL_EPSILON) || (fabs(c - b) < DBL_EPSILON))
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it = m+1;
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else if (sgn_c == sgn_a)
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{
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a = c;
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y_a = y;
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} else if (sgn_c == sgn_b)
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{
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b = c;
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y_b = y;
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}
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}
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if (it > m)
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it = -1;
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*x = c;
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return it;
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}
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