{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

ode_exp_rk2

# ode_exp_rk2 - yin[0 = y[i rk2(x[i yin yout h do one...

This preview shows pages 1–2. Sign up to view the full content.

/* ode_exp_euler.c * Example code to solve dy/dx=y using second order Runge-Kutta. */ #include <stdio.h> #define N 1 /* number of ODEs */ #define NSTEP 10 /* number of integration steps */ #define XMIN 0.0 /* starting point for integration */ #define XMAX 1.0 /* stopping point for integration */ #define Y0 1.0 /* initial value */ void derivs(float xin, float yin[], float dydx[]); void rk2(float xin, float yin[], float yout[], float h); int main() { int i; float h = (XMAX - XMIN)/(1.0*NSTEP); /* stepsize for integration */ float yin[N], yout[N]; /* values of y before and after a step, for a given x */ float x[NSTEP+1], y[NSTEP+1]; for (i = 0; i <= NSTEP; i++) /* Define array of x values */ x[i] = XMIN + h * i; y[0] = Y0; /* initial value */ printf("%f %f\n", x[0], y[0]); for (i = 0; i < NSTEP; i++) /* loop over x values */

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: { yin[0] = y[i]; rk2(x[i], yin, yout, h); /* do one integration step */ y[i+1] = yout[0]; printf("%f %f\n", x[i+1], y[i+1]); } return 0; } void derivs(float xin, float yin, float dydx) { /* evaluate RHS of ODE */ dydx[0] = yin[0]; return; } void rk2(float xin, float yin, float yout, float h) { /* Second order Runge-Kutta scheme */ int i; float k1[N], k2[N], yt[N], dydx[N]; /* N is the number of ODEs */ /* Evaluate k1 */ derivs(xin, yin, dydx); for (i = 0; i < N; i++) { k1[i] = h*dydx[i]; yt[i] = yin[i] + 0.5*k1[i]; } /* Evaluate k2, then update the dependent variable */ derivs(xin + 0.5*h, yt, dydx); for (i = 0; i < N; i++) { k2[i] = h*dydx[i]; yout[i] = yin[i] + k2[i]; } return; }...
View Full Document

{[ snackBarMessage ]}