Function intdei
I = integral of f(x) over (a,infinity), f(x) has not oscillatory factor.
void intdei(Real, Func)
(
Func f,
Real a,
Real eps,
Real* i,
Real* err
);
Parameters
Name | Description |
---|---|
f | integrand f(x) |
a | lower limit of integration |
eps | relative error requested |
i | approximation to the integral |
err | estimate of the absolute error |
Remarks
function f(x) needs to be analytic over (a,infinity). relative error eps is relative error requested excluding cancellation of significant digits. i.e. eps means : (absolute error) / (integral_a^infinity |f(x)| dx). eps does not mean : (absolute error) / I. error message err >= 0 : normal termination. err < 0 : abnormal termination (m >= mmax). i.e. convergent error is detected : 1. f(x) or (d/dx)^n f(x) has discontinuous points or sharp peaks over (a,infinity). you must divide the interval (a,infinity) at this points. 2. relative error of f(x) is greater than eps. 3. f(x) has oscillatory factor and decay of f(x) is very slow as x -> infinity.