57 lines
1.5 KiB
C
57 lines
1.5 KiB
C
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#include "integrate.h"
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#include <math.h>
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#include <stdio.h>
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typedef struct
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{
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float a2, a1, a0;
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} quad_t;
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static float f_quad(float x, void *ctx)
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{
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const quad_t *q = (const quad_t *)ctx;
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return (q->a2 * x * x) + (q->a1 * x) + q->a0;
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}
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static void run_one(const char *name, integrand_f f, void *ctx, float a,
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float b, float exact, unsigned n)
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{
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float r = 0.0f, t = 0.0f, s = 0.0f;
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integ_status_t stS;
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midpoint(f, ctx, a, b, n, &r);
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trapezoid(f, ctx, a, b, n, &t);
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stS = simpson(f, ctx, a, b, n, &s);
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printf("\n%s on [%.6f, %.6f], n=%u\n", name, a, b, n);
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printf("Exact: %.9f\n", exact);
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printf("Midpoint: %.9f err=%.9f\n", r, fabsf(r - exact));
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printf("Trapezoid: %.9f err=%.9f\n", t, fabsf(t - exact));
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if (stS == INTEG_OK)
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printf("Simpson: %.9f err=%.9f\n", s, fabsf(s - exact));
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else
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printf("Simpson: not computed (n must be even)\n");
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}
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int main(void)
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{
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const quad_t q = {1.0f, 0.0f, 0.0f}; /*x^2*/
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const quad_t q2 = {-1.0f, 3.0f, 50.0f}; /*x^2+3x+50*/
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const quad_t q3 = {-9.0f, 3.0f, -100.0f}; /*-9x^2+3x-100*/
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const quad_t q4 = {6.0f, -10.0f, 0.0f}; /*6x^2-10x*/
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run_one("x^2", f_quad, (void *)&q, 0.0f, 1.0f, 1.0f / 3.0f, 10u);
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run_one("x^2+3x+50", f_quad, (void *)&q2, -3.0f, 15.0f, 90.0f, 22u);
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run_one("-9x^2+3x-100", f_quad, (void *)&q3, 12.0f, 15.0f, -5119.5f, 2u);
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run_one("6x^2-10x", f_quad, (void *)&q4, -50.0f, -5.0f, 262125.0f, 6u);
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return 0;
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}
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