ModSim ass4 taddeus: Source code cleanup.

modsim/ass4_taddeus/vibstring/seq.c

@@ -3,47 +3,35 @@
 #include <string.h>
 #include <math.h>
 
-double **create_y(int steps) {
-    double **y = (double **)malloc(3 * sizeof(double *));
-    int i;
-
-    if( y == NULL ) {
-        puts("Error: could not allocate memory.");
-        exit(EXIT_FAILURE);
-    }
-
-    for( i = 0; i < 3; i++ )
-        y[i] = (double *)malloc(steps * sizeof(double));
-
-    return y;
-}
+double **y = NULL, dx;
+int x_steps, calc_steps, print_resolution;
 
 /*
  *
  */
-void init_sinus(double **y, int steps, double l, double dx, double n) {
-    for( int i = 0; i < steps; i++ )
+void init_sinus(double l, double n) {
+    for( int i = 0; i < x_steps; i++ )
         y[0][i] = sin(n * M_PI * i * dx / l);
 
     // The string is attached at both ends
     y[2][0] = y[1][0] = y[0][0];
-    y[2][steps - 1] = y[1][steps - 1] = y[0][steps - 1];
+    y[2][x_steps - 1] = y[1][x_steps - 1] = y[0][x_steps - 1];
 }
 
 /*
  *
  */
-void init_plucked(double **y, int steps, double l, double dx, double xp) {
+void init_plucked(double l, double xp) {
     double x;
 
-    for( int i = 0; i < steps; i++ ) {
+    for( int i = 0; i < x_steps; i++ ) {
         x = i * dx;
         y[0][i] = x < xp ? x / xp : (l - x) / (l - xp);
     }
 
     // The string is attached at both ends
     y[2][0] = y[1][0] = y[0][0];
-    y[2][steps - 1] = y[1][steps - 1] = y[0][steps - 1];
+    y[2][x_steps - 1] = y[1][x_steps - 1] = y[0][x_steps - 1];
 }
 
 #define VERBOSE
@@ -51,12 +39,12 @@ void init_plucked(double **y, int steps, double l, double dx, double xp) {
 #ifdef VERBOSE
 #define PRINT_FORMAT "%e"
 
-void print(double *y, int string_steps) {
-    for( int i = 0; i < string_steps; i++ ) {
+void print(int index) {
+    for( int i = 0; i < x_steps; i++ ) {
         if( i )
             printf(" ");
 
-        printf(PRINT_FORMAT, y[i]);
+        printf(PRINT_FORMAT, y[index][i]);
     }
 
     puts("");
@@ -66,14 +54,13 @@ void print(double *y, int string_steps) {
 /*
  *
  */
-void iterate(double **y, int string_steps, double dx, int calc_steps,
-        int print_resolution, double tau) {
+void calculate_steps(int calc_steps, int print_resolution, double tau) {
     double x;
     int i, t, prev = 0, current = 1, next = 2;
 
     // 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++ ) {
+    for( i = 1; i < x_steps - 1; i++ ) {
         x = i * dx;
         y[1][i] = y[0][i] + .5 * tau * tau * (y[0][i-1] - 2 * y[0][i]
                   + y[0][i+1]);
@@ -81,7 +68,7 @@ void iterate(double **y, int string_steps, double dx, int calc_steps,
 
     #ifdef VERBOSE
     // Print x values (which are the same for every y-series)
-    for( i = 0; i < string_steps; i++ ) {
+    for( i = 0; i < x_steps; i++ ) {
         if( i )
             printf(" ");
 
@@ -91,22 +78,22 @@ void iterate(double **y, int string_steps, double dx, int calc_steps,
     puts("");
 
     // Print init states
-    print(y[prev], string_steps);
+    print(prev);
 
     if( print_resolution == 1 )
-        print(y[current], string_steps);
+        print(current);
     #endif
 
     // Iterate over the length of the string for each time interval step
     for( t = 2; t < calc_steps; t++ ) {
-        for( i = 1; i < string_steps - 1; i++ ) {
+        for( i = 1; i < x_steps - 1; i++ ) {
             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
         if( !(t % print_resolution) )
-            print(y[next], string_steps);
+            print(next);
         #endif
 
         prev = current;
@@ -116,10 +103,11 @@ void iterate(double **y, int string_steps, double dx, int calc_steps,
 }
 
 int main(int argc, const char **argv) {
-    int x_steps, calc_steps, i, print_resolution;
-    void (*init_method)(double **, int, double, double, double);
-    double **y, l, dx, tau, constant;
+    int calc_steps, i, print_resolution;
+    void (*init_method)(double, double);
+    double l, tau, constant;
 
+    // Parse argument
     if( argc < 8 ) {
         printf("Usage: %s INIT_METHOD CALCULATION_STEPS PRINT_RESOLUTION LENGTH"
                " DX TAU N|XP\n", argv[0]);
@@ -142,10 +130,23 @@ int main(int argc, const char **argv) {
     tau = atof(argv[6]);
     constant = atof(argv[7]);
 
+    // Allocate a 3xN two-dimensional area that functions as a cyclic buffer
+    // for three states of the string (previous, current, next)
     x_steps = (int)ceil(l / dx);
-    y = create_y(x_steps);
-    (*init_method)(y, x_steps, l, dx, constant);
-    iterate(y, x_steps, dx, calc_steps, print_resolution, tau);
+
+    if( (y = (double **)malloc(3 * sizeof(double *))) == NULL ) {
+        puts("Error: could not allocate memory.");
+        exit(EXIT_FAILURE);
+    }
+
+    for( i = 0; i < 3; i++ )
+        y[i] = (double *)malloc(x_steps * sizeof(double));
+
+    // Initialize the string values (sinus/plucked)
+    (*init_method)(l, constant);
+
+    // Calculate the specified number of steps
+    calculate_steps(calc_steps, print_resolution, tau);
 
     // Free allocated memory
     for( i = 0; i < 3; i++ )