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#include <ctime>
#include <iostream>
using namespace std;
#include <ginac/ginac.h>
using namespace GiNaC;
/*
* 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()
{
// Define some expression
symbol x("x");
ex expr = sin(x);
// 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;
}
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