bugGNU Scientific Library - Bugs: bug #59911, Problem with qagui 1D integrator


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bug #59911: Problem with qagui 1D integrator

Submitter:  Patrick Alken <psa>
Submitted:  Wed 20 Jan 2021 02:36:50 AM UTC
Category:  None Severity:  3 - Normal
Operating System:  Status:  None
Assigned to:  None Open/Closed:  Open

Wed 10 Mar 2021 08:02:06 PM UTC, comment #1: 

cosh(x) dx is d(sh x). If you name that variable u, you have an integral of exp(-sqrt(1+u^2)). This function seems to better behave at infinity, it doesn't have accuracy errors because as the previous product of a very large and very small function.

Yaroslav Nikitenko <ynikitenko>
Wed 20 Jan 2021 02:36:50 AM UTC, original submission:  

from takacs =dot= adam =at= wigner =dot= mta =dot= hu

Dear GSL Helpers,

We tried to use the qagiu algorithm to calculate the following integration

   \int_0^infty dx cosh(x) e^{-cosh(x)} ,

however qagiu falls and complains on "bad integrand behavior". If we're
using qags with a fixed big upper limit, the integral is fine.

Do you have any suggestion what could be the problem? We'd like to
use qagiu without upper limit.

Patrick Alken <psa>
Group administrator


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