ModSim ass4 taddeus: Source code cleanup.

modsim/ass4_taddeus/vibstring/seq.c

@@ -4,7 +4,7 @@
 #include <math.h>
 
 double **create_y(int steps) {
-    double **y = (double **)malloc(steps * sizeof(double *));
+    double **y = (double **)malloc(3 * sizeof(double *));
     int i;
 
     if( y == NULL ) {
@@ -12,8 +12,8 @@ double **create_y(int steps) {
         exit(EXIT_FAILURE);
     }
 
-    for( i = 0; i < steps; i++ )
-        y[i] = (double *)malloc(3 * sizeof(double));
+    for( i = 0; i < 3; i++ )
+        y[i] = (double *)malloc(steps * sizeof(double));
 
     return y;
 }
@@ -23,11 +23,11 @@ double **create_y(int steps) {
  */
 void init_sinus(double **y, int steps, double l, double dx, double n) {
     for( int i = 0; i < steps; i++ )
-        y[i][0] = sin(n * M_PI * i * dx / l);
+        y[0][i] = sin(n * M_PI * i * dx / l);
 
     // The string is attached at both ends
-    y[0][2] = y[0][1] = y[0][0];
-    y[steps - 1][2] = y[steps - 1][1] = y[steps - 1][0];
+    y[2][0] = y[1][0] = y[0][0];
+    y[2][steps - 1] = y[1][steps - 1] = y[0][steps - 1];
 }
 
 /*
@@ -38,64 +38,63 @@ void init_plucked(double **y, int steps, double l, double dx, double xp) {
 
     for( int i = 0; i < steps; i++ ) {
         x = i * dx;
-        y[i][0] = x < xp ? x / xp : (l - x) / (l - xp);
+        y[0][i] = x < xp ? x / xp : (l - x) / (l - xp);
     }
 
     // The string is attached at both ends
-    y[0][2] = y[0][1] = y[0][0];
-    y[steps - 1][2] = y[steps - 1][1] = y[steps - 1][0];
+    y[2][0] = y[1][0] = y[0][0];
+    y[2][steps - 1] = y[1][steps - 1] = y[0][steps - 1];
 }
 
 #define VERBOSE
+
+#ifdef VERBOSE
 #define PRINT_FORMAT "%e"
 
+void print(double **y, int time_step, int t, int string_steps, double dx) {
+    printf("%d", time_step);
+
+    for( int i = 0; i < string_steps; i++ )
+        printf(" " PRINT_FORMAT " " PRINT_FORMAT, i * dx, y[t][i]);
+
+    puts("");
+}
+#endif
+
 /*
  *
  */
-void iterate(double **y, int string_steps, double dx, int time_steps, double dt,
-        double theta) {
+void iterate(double **y, int string_steps, double dx, int count, int stride,
+        double tau) {
     double x;
-    int i, t, prev = 0, current = 1, next = 2;
+    int i, t, prev = 0, current = 1, next = 2, time_steps = count * stride;
 
     // Calculate the position over the entire string at time dt using the
     // position at t = 0 and the information that y(x, -dt) == y(x, dt)
     for( i = 1; i < string_steps - 1; i++ ) {
         x = i * dx;
-        y[i][1] = y[i][0] + .5 * theta * theta * (y[i-1][0] - 2 * y[i][0]
-                  + y[i+1][0]);
+        y[1][i] = y[0][i] + .5 * tau * tau * (y[0][i-1] - 2 * y[0][i]
+                  + y[0][i+1]);
     }
 
-    // Print init states
     #ifdef VERBOSE
-    for( t = 0; t < 2; t++ ) {
-        printf(PRINT_FORMAT, t * dt);
-
-        for( i = 0; i < string_steps; i++ )
-            printf(" " PRINT_FORMAT " " PRINT_FORMAT, i * dx, y[i][t]);
+    // Print init states
+    print(y, 0, 0, string_steps, dx);
 
-        puts("");
-    }
+    if( stride == 1 )
+        print(y, 1, 1, string_steps, dx);
     #endif
 
     // Iterate over the length of the string for each time interval step
     for( t = 2; t < time_steps; t++ ) {
-        #ifdef VERBOSE
-        printf(PRINT_FORMAT " " PRINT_FORMAT " " PRINT_FORMAT, t * dt, .0,
-               y[0][next]);
-        #endif
-
         for( i = 1; i < string_steps - 1; i++ ) {
-            y[i][next] = 2 * y[i][current] - y[i][prev] + theta * theta
-                * (y[i-1][current] - 2 * y[i][current] + y[i+1][current]);
-
-            #ifdef VERBOSE
-            printf(" " PRINT_FORMAT " " PRINT_FORMAT, i * dx, y[i][next]);
-            #endif
+            y[next][i] = 2 * y[current][i] - y[prev][i] + tau * tau
+                * (y[current][i-1] - 2 * y[current][i] + y[current][i+1]);
         }
 
         #ifdef VERBOSE
-        printf(" " PRINT_FORMAT " " PRINT_FORMAT "\n", (string_steps - 1) * dx,
-               y[string_steps - 1][next]);
+        if( !(t % stride) )
+            print(y, t, next, string_steps, dx);
         #endif
 
         prev = current;
@@ -105,12 +104,12 @@ void iterate(double **y, int string_steps, double dx, int time_steps, double dt,
 }
 
 int main(int argc, const char **argv) {
-    int steps, i;
+    int steps, i, count, stride;
     void (*init_method)(double **, int, double, double, double);
-    double **y, t, dt, l, dx, theta, constant;
+    double **y, l, dx, tau, constant;
 
     if( argc < 8 ) {
-        printf("Usage: %s INIT_METHOD TIME DT LENGTH DX THETA N|XP\n", argv[0]);
+        printf("Usage: %s INIT_METHOD COUNT STRIDE LENGTH DX TAU N|XP\n", argv[0]);
         return EXIT_FAILURE;
     }
 
@@ -123,19 +122,19 @@ int main(int argc, const char **argv) {
         return EXIT_FAILURE;
     }
 
-    t = atof(argv[2]);
-    dt = atof(argv[3]);
+    count = atoi(argv[2]);
+    stride = atoi(argv[3]);
     l = atof(argv[4]);
     dx = atof(argv[5]);
-    theta = atof(argv[6]);
+    tau = atof(argv[6]);
     constant = atof(argv[7]);
 
     y = create_y(steps = (int)ceil(l / dx));
     (*init_method)(y, steps, l, dx, constant);
-    iterate(y, steps, dx, (int)ceil(t / dt), dt, theta);
+    iterate(y, steps, dx, count, stride, tau);
 
     // Free allocated memory
-    for( i = 0; i < steps; i++ )
+    for( i = 0; i < 3; i++ )
         free(y[i]);
 
     free(y);