Finished assignment 6.

modsim/ass2/q6.c

@@ -4,18 +4,26 @@
 #include "func_ptr.h"
 #include "integral.h"
 
-#define STRIDE 10000
-
 double accurate_integral(func_ptr f, method_ptr method, double a,
-        double b, double accuracy, unsigned int stride) {
-    unsigned int steps = 0;
-    double result, old;
+        double b, double accuracy, unsigned int decimals) {
+    unsigned int steps = 5000, i, prefix;
+    double result = 0, old = 1;
 
-    do {
-        steps += stride;
+    while( fabs(old - result) >= accuracy ) {
+        steps *= 2;
         old = result;
         result = integral(f, method, a, b, steps);
-    } while( fabs(old - result) >= accuracy );
+    }
+
+    for( decimals += 2, prefix = (int)result; prefix; prefix /= 10 )
+        decimals++;
+
+    printf("%.30f\n", old);
+
+    for( i = 0; i < decimals; i++ )
+        printf(" ");
+
+    printf("| could deviate from here\n%.30f\n", result);
 
     return result;
 }
@@ -24,12 +32,21 @@ double f1(double x) {
     return x * pow(M_E, -x);
 }
 
-#define PRINT_INTEGRAL(func, method, a, b, acc) (printf(#func " from " #a " to " \
-    #b " using %-19s %.11e", accurate_itegral(&func, &method, a, b, acc, STRIDE), \
-    #method " method:"))
+#define PRINT_INTEGRAL(func, method, a, b, decimals) { \
+    double real = 0; \
+    double _i = accurate_integral(&func, &method, a, b, \
+            pow(10, -1.0 * decimals), decimals); \
+    printf(#func " from " #a " to " #b " using %-19s %.11e (%.8e%%)\n", \
+           #method " method:", _i, fabs(_i - real)); \
+}
+
+int main(int argc, char *argv[]) {
+    if( argc != 2 ) {
+        printf("Usage: %s DECIMALS", argv[0]);
+        return 1;
+    }
 
-int main(void) {
-    PRINT_INTEGRAL(f1, gauss, 0, 2, 1e-5);
+    PRINT_INTEGRAL(f1, gauss, 0, 2, atoi(argv[1]));
 
     return 0;
 }