ModSim ass4 part 1 and 2 are not finished.

modsim/ass4_sander/part1/start.sh

 #!/bin/sh
 NUM_PROCESSES=4
-HOSTS=ow130,ow131
+HOSTS=deleuze,localhost
 PROGRAM_EXEC=main
 
 mpirun -np $NUM_PROCESSES -H $HOSTS $PROGRAM_EXEC

modsim/ass4_sander/part2/Makefile

-CFLAGS +=-std=c99 -Wall -Wextra -g -O2 -pthread
+CFLAGS +=-std=c99 -Wall -Wextra -pedantic -g -O2 -pthread -D_GNU_SOURCE
 LDFLAGS+=-pthread -lmpi -lopen-rte -lopen-pal -ldl -Wl,--export-dynamic \
 		 -lnsl -lutil -lm -ldl
 

modsim/ass4_sander/part2/main.c

@@ -2,84 +2,120 @@
 #include <stdlib.h>
 #include <stdio.h>
 
-#define GRID_LENGTH 64
+#define STRING_PARTS len
 
-double Y[GRID_LENGTH][3];
+int STRING_PARTS;
+double *Y;
 int t_next, t_prev, t_cur;
 
-void init_sinus(char **argv) {
-    double amp;
-    int h_phases;
+/*
+ * Macros used to manipulate the allocated memory for Y.
+ */
+#define GET_Y(i, t) \
+    Y[i + t * STRING_PARTS]
 
-    sscanf(argv[2], "%lf", &amp);
-    sscanf(argv[3], "%i", &h_phases);
-    for( int i = 0; i < GRID_LENGTH; i++ ) {
-        Y[i][t] = amp * sin(M_PI * (i(double)/(double)GRID_LENGTH) * h_phases);
-    }
-}
+#define SET_Y(i, t, val) \
+    Y[i + t * STRING_PARTS] = val
 
-void init_pluck(char **argv) {
-    double amp, position;
-    int ipos, i;
+/*
+ * Fill the allocated memory for Y with a sinus shape.
+ */
+static void init_sinus(int phases) {
+    double c = (double) (STRING_PARTS * phases) * M_PI ;
 
-    sscanf(argv[2], "%lf", &amp);
-    sscanf(argv[3], "%i", &position);
+    for( int i = 0; i < STRING_PARTS; i++ ) {
+        SET_Y(i, 0, sin(((double) i) / c));
+    }
+}
 
-    ipos = position / dx * GRID_LENGTH;
+/*
+ * Fill the allocated memory for Y with a pluck shape.
+ */
+static void init_pluck(double pluck, double length, double dx) {
+    int ipos = ((int) dx) + 1, i;
+    fprintf(stderr, "ipos: %d\n", ipos);
 
     for( i = 0; i < ipos; i++ ) {
-        Y[i][t] = i * dx / position * amp;
+        SET_Y(i, 0, i * dx / pluck);
     }
-    for(;i < GRID_LENGTH; i++ ) {
-        Y[i][t] = ((GRID_LENGTH - i) * dx) / (GRID_LENGTH - ipos) * amp;
+
+    for( ; i < STRING_PARTS; i++ ) {
+        SET_Y(i, 0, ((STRING_PARTS - i) * dx) / (STRING_PARTS - ipos));
     }
 }
 
-void iterate(double C, int t_prev, int t_cur, int t_next) {
-    for( int i = 1; i < GRID_LENGTH; i++ ) {
-        Y[i][t_next] = C * (Y[i-1][t_cur] - 2*Y[i][t_cur] + Y[i+1][t_cur])
-            - Y[i][t_prev]
-            + 2 * Y[i][t_cur];
+static void connect_string_ends() {
+    const int end = STRING_PARTS - 1;
+    Y[STRING_PARTS * 2] = Y[STRING_PARTS * 1] = Y[STRING_PARTS];
+    Y[STRING_PARTS * 2 + end] = Y[STRING_PARTS * 1 + end] = Y[STRING_PARTS + end];
+}
+
+/*
+ * Calculate position over the entire string at time 't_cur' (= dt).
+ */
+static void iterate(double C, int t_prev, int t_cur, int t_next) {
+    for( int i = 1, max = STRING_PARTS - 1; i < max; i++ ) {
+        SET_Y(i, t_next, \
+            C * (GET_Y(i-1, t_cur) - 2 * GET_Y(i, t_cur) + GET_Y(i+1, t_cur))
+            - GET_Y(i, t_prev)
+            + 2 * GET_Y(i, t_cur));
     }
 }
 
+/*
+ * Integer XOR swapping macro.
+ */
 #define SWAP(a, b) \
     a ^= b; \
     b ^= a; \
     a ^= b;
 
+static void plot(int col) {
+    printf("%e", GET_Y(0, col));
+
+    for( int i = 1; i < STRING_PARTS; i++ )
+        printf(",%e", GET_Y(i, col));
 
-void plot(int col) {
-    printf("%f", Y[0][col]);
-    for( int i = 1; i < GRID_LENGTH; i++ )
-        printf(",%f", Y[i][col]);
     printf("\n");
 }
 
-int main(int argc, char**argv) {
+int main(int argc, char **argv) {
 
-    if(argc < 4) {
-        fprintf(stderr, "Usage: %s <p amplitude position |s amplitude phases", argv[0]);
+    if(argc < 7) {
+        fprintf(stderr, "Usage: %s <p|s> ITERATIONS LENGTH STEP_SIZE"\
+                        " TAU <PLUCK|PHASES>\n",
+                argv[0]);
         return 1;
     }
 
+    // Initialise time indices, iterations and string length.
+    int t_prev = 0, t_cur = 1, t_next = 2,
+        iterations = atoi(argv[2]),
+        length = atoi(argv[3]);
+
+    double dx = atof(argv[4]),
+        tau = atof(argv[5]);
+
+    STRING_PARTS = length / dx;
+
+    if( !(Y = (double *) malloc(3 * STRING_PARTS * sizeof(double))) )
+        return 2;
+
+    // Initialise the requested shape in the allocated memory.
     switch(*argv[1]) {
-    case 'p': init_pluck(argv); break;
-    case 's': init_sinus(argv); break;
+    case 'p': init_pluck(atof(argv[6]), length, dx); break;
+    case 's': init_sinus(atoi(argv[6])); break;
     default:
-        fprintf(stderr, "Does this look like a 'p' or 's' to you?\n");
+        fprintf(stderr, "Argument 2 '%s' does not look like a 'p' or 's'.\n",
+                argv[1]);
         return 1;
     }
 
-    double c = .04, dt = .1, dx = .02,
-        C = c * c * (dt/dx) * (dt/dx);
-
-    // TODO: implement iterations
-    int t_prev = 0, t_cur = 1, t_next = 2,
-        T = 10;
+    // The string is connected at both ends.
+    connect_string_ends();
 
-    for( int i = 0; i < T; i++ ) {
-        iterate(C, t_prev, t_cur, t_next);
+    for( int i = 0; i < iterations; i++ ) {
+        iterate(tau, t_prev, t_cur, t_next);
         SWAP(t_cur, t_next);
         SWAP(t_prev, t_next);
         plot(t_cur);

modsim/ass4_sander/part2/plot.py

-from pyplot import show, fig
+#!/usr/bin/env python
+from pylab import plot, figure, clf, show
+from sys import stdin
 
+lines = stdin.readlines()
+Y = map(float, lines[0].split(','))
+
+figure(1)
+clf()
+
+plot(Y, '-')
+
+show()