New examples for compile_ex and link_ex.

[ginac.git] / doc / examples / compile1.cpp

diff --git a/doc/examples/compile1.cpp b/doc/examples/compile1.cpp
index e2fa8e022f4b261a25bf3f49a76622bd1942b025..cc81229e84c2ac721613696552253337f85b0c31 100644 (file)
--- a/doc/examples/compile1.cpp
+++ b/doc/examples/compile1.cpp
@@ -1,45 +1,69 @@
+#include <ctime>
 #include <iostream>
 using namespace std;
 #include <ginac/ginac.h>
 using namespace GiNaC;
-// Yes, we are using CUBA (should be installed on the system!)
-#include "cuba.h"
+
+/*
+ * Demonstrates the use of compile_ex.
+ *
+ * Compiles a small expression as C code via compile_ex and evaluates the
+ * expression numerically. The evalation speed is timed and compared to the
+ * evaluation of the original GiNaC expression.
+ *
+ */
 
 int main()
 {
-       // Let the user enter a expression
-       symbol x("x"), y("y");
-       string s;
-       cout << "Enter an expression containing 'x' and/or 'y': ";
-       cin >> s;
-       // Expression now in expr
-       ex expr(s, lst(x,y));
+       // Define some expression
+       symbol x("x");
+       ex expr = sin(x);
  
-       cout << "start integration of " << expr << " ..." << endl;
-
-       // Some definitions for VEGAS 
-       #define NDIM 2
-       #define NCOMP 1
-       #define EPSREL 1e-3
-       #define EPSABS 1e-12
-       #define VERBOSE 0
-       #define MINEVAL 0
-       #define MAXEVAL 50000
-       #define NSTART 1000
-       #define NINCREASE 500
-
-       // Some variables for VEGAS
-       int comp, nregions, neval, fail;
-       double integral[NCOMP], error[NCOMP], prob[NCOMP];
-
-       // Starting VEGAS
-       // By invocation of compile() the expression in expr is converted into the
-       // appropriate function pointer
-       Vegas(NDIM, NCOMP, compile(lst(expr), lst(x,y)), EPSREL, EPSABS, VERBOSE,
-             MINEVAL, MAXEVAL, NSTART, NINCREASE, &neval, &fail, integral, error, prob);
-
-       // Show the result
-       cout << "result: " << integral[0] << endl;
+       // Some variables for timing
+       time_t start, end;
+       double cpu_time_used;
+
+       // Our function pointer that points to the compiled ex
+       FUNCP_1P fp;
+       compile_ex(expr, x, fp);
+
+       // Do some (not necessarily meaningful ;-)) numerical stuff ...
+
+       cout << "Doing numerics with compile_ex ..." << endl;
+
+       // First using compile_ex
+       {
+               double result;
+               double point = 0.2;
+               start = clock();
+               for (int i=0; i<100000; ++i) {
+                       point += 0.001;
+                       result += fp(point);
+               }
+               end = clock();
+
+               // Show the result
+               cpu_time_used = ((double) (end - start)) / CLOCKS_PER_SEC;
+               cout << "result = " << result << " in " << cpu_time_used << " seconds" << endl;
+       }
+
+       cout << "Doing numerics without compile_ex ..." << endl;
+
+       // Then without compile_ex
+       {
+               ex result;
+               ex point = 0.2;
+               start = clock();
+               for (int i=0; i<100000; ++i) {
+                       point += 0.001;
+                       result += sin(point);
+               }
+               end = clock();
+
+               // Show the other result
+               cpu_time_used = ((double) (end - start)) / CLOCKS_PER_SEC;
+               cout << "result = " << result << " in " << cpu_time_used << " seconds" << endl;
+       }
 
        return 0;
 }