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Originally posted by yalefield at 2009-12-7 00:05:
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Originally posted by holmescn at 2009-12-18 15:33:
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Originally posted by ²¨²»¶¯ at 2009-12-18 19:40:


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#include
#include
#include
#include

// Function to be integrated
// Define and prototype it here
// | sin(x) |
#define INTEG_FUNC(x) fabs(sin(x))

// Prototype timing function
double dclock(void);

int main(void)
{
// Loop counters and number of interior points
unsigned int i, j, N;
// Stepsize, independent variable x, and accumulated sum
double step, x_i, sum;
// Timing variables for evaluation
double start, finish, duration, clock_t;
// Start integral from
double interval_begin = 0.0;
// Complete integral at
double interval_end = 2.0 * 3.141592653589793238;

// Start timing for the entire application
start = clock();

printf(" \n");
printf(" Number of | Computed Integral | \n");
printf(" Interior Points | | \n");
for (j=2;j<27;j++)
{
printf("------------------------------------- \n");

// Compute the number of (internal rectangles + 1)
N = 1 << j;

// Compute stepsize for N-1 internal rectangles
step = (interval_end - interval_begin) / N;

// Approx. 1/2 area in first rectangle: f(x0) * [step/2]
sum = INTEG_FUNC(interval_begin) * step / 2.0;

// Apply midpoint rule:
// Given length = f(x), compute the area of the
// rectangle of width step
// Sum areas of internal rectangle: f(xi + step) * step

for (i=1;i {
x_i = i * step;
sum += INTEG_FUNC(x_i) * step;
}

// Approx. 1/2 area in last rectangle: f(xN) * [step/2]
sum += INTEG_FUNC(interval_end) * step / 2.0;

printf(" %10d | %14e | \n", N, sum);
}
finish = clock();
duration = (finish - start);
printf(" \n");
printf(" Application Clocks = %10e \n", duration);
printf(" \n");

return 0;
}

Originally posted by holmescn at 2009-12-21 16:05:
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Originally posted by holmescn at 2009-12-21 16:05:
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icc 0.249s

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Originally posted by ²¨²»¶¯ at 2009-12-21 19:16:


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