Modsim ass3: Started work on question 1 (harmonic oscillator).

modsim/ass3/Makefile

@@ -2,10 +2,13 @@ CC=gcc
 CFLAGS=-Wall -Wextra -pedantic -std=c99 -D_GNU_SOURCE -g -O0
 LFLAGS=-lm
 
-all: test
+all: test harm_osc
 
 test: test.o methods.o
 	$(CC) $(CFLAGS) $(LFLAGS) -o $@ $^
 
+harm_osc: harm_osc.o methods.o
+	$(CC) $(CFLAGS) $(LFLAGS) -o $@ $^
+
 clean:
-	rm *.o test
+	rm *.o test harm_osc

modsim/ass3/harm_osc.c

+#include <stdlib.h>
+#include <stdio.h>
+#include <math.h>
+#include "methods.h"
+
+#define DT .001
+
+#define INTEGRATE(method, t0, t1) { \
+    if( method(t0, t1, DT, y0, y1, 2, &f_osc, &k) ) \
+        puts("FAIL"); \
+    else \
+        printf("y1 using %-12s s:%.10f\n", #method ":", *y1); \
+}
+#define COMPARE(t0, t1) { \
+    INTEGRATE(Euler, t0, t1); \
+    INTEGRATE(RungeKutta2, t0, t1); \
+    INTEGRATE(RungeKutta4, t0, t1); \
+}
+/*
+void log(double t, double *y) {
+    printf("%f,%f,%f\n", t, y[0], y[1]);
+}
+*/
+int f_osc(double t, double *y, double *dy, void *params) {
+    dy[0] = y[1];
+    dy[1] = -*(double *)(params) * y[0];
+
+    return 0;
+}
+
+int main(void) {
+    double k = .5, y0[2] = {.0, 5.0}, y1[2] = {.0, .0};
+
+    COMPARE(.0, 10.0)
+
+    return 0;
+}