ex-5: rearranged everything

ex-5/casino.c

@@ -1,37 +0,0 @@
-#include <stdio.h>
-#include <math.h>
-#include <stdlib.h>
-#include <gsl/gsl_rng.h>
-
-int main(int argc, char** argv){
-  size_t size = atoi(argv[1]);             // size of the generated sample
-
-  // Initialize an RNG.
-  gsl_rng_env_setup();
-  gsl_rng *r = gsl_rng_alloc(gsl_rng_default);
-
-  // Random points (x, y) generation: x in [0,1), y in [0,3)
-  // get if   y < exp(x)
-  // leave if y > exp(x)
-  size_t in = 0;
-  size_t total = 0;
-  do{
-    double x = gsl_rng_uniform(r);
-    double y = 3 * gsl_rng_uniform(r);
-    if (y <= exp(x)){
-      in++;
-    }
-    total++;
-  } while (total < size);
-
-  
-  // The integral is esitmated thorugh the proportion:
-  // integral : 3 = in : total
-  double integral = 3.0*(double)in/(double)total;
-  printf("∫exp(x)dx in [0,1]:\t%.07f\n", integral);
-
-  // Free memory
-  gsl_rng_free(r);
-  return EXIT_SUCCESS;
-}
-

ex-5/main.c

@@ -5,10 +5,6 @@
 #include <math.h>
 
 
-// Exact value of the integral.
-double exact = 1.71828182845905;
-
-
 // Function which must be passed to the gsl_function.
 double function (double * x, size_t dim, void * params){
   // Avoid warning when no parameters are passed to the function.
@@ -23,14 +19,24 @@ void results (char *title, double result, double error)
   printf ("---------------------------\n%s\n", title);
   printf ("result:  % .10f\n", result);
   printf ("sigma:   % .10f\n", error);
-  printf ("exact:   % .10f\n", exact);
 } 
 
 
-int main(){
+int main(int argc, char** argv){
+
+  // If no argument is given is input, an error signal is displayed
+  // and the program quits.
+
+  if (argc != 2)
+    {
+    fprintf(stderr, "usage: %s D\n", argv[0]);
+    fprintf(stderr, "Computes the integral generating D points.\n");
+    return EXIT_FAILURE;
+    }
+
   // Some useful variables.
   double integral, error;
-  size_t calls = 50000000;
+  size_t calls = 5000;
   size_t dims = 1;
   double lower[1] = {0};    // Integration lower limit
   double upper[1] = {1};    // Integration upper limit

ex-5/manual.c

@@ -1,31 +0,0 @@
-#include <math.h>
-#include <stdio.h>
-#include <stdlib.h>
-
-/* This program evaluates the integral of exp(x) in [0;1] through the
- * trapezoidal rule.
- * The integration step is given in input as d in step = 1e-d.
- *
- */
-
-int main(int argc, char** argv){
-  double left = 0;                         // left limit
-  double point = left;                     // points at the current position
-  double right = 1;                        // right limit
-
-  double step = pow(10, -atoi(argv[1]));   // step of integration
-
-  double sum = 0;
-
-  // Integral evaluation: stops when point goes over the right edge of the
-  // range.
-  do {
-    sum += step * 0.5 * (exp(point) + exp(point + step));
-    point += step;
-  } while (point < right);
-
-  // Print out the result
-  printf("∫exp(x)dx in [0,1]:\t%.7f\n", sum);
-
-  return EXIT_SUCCESS;
-}