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## Re: [Bug-gsl] gsl_integration_qagiu failure

**From**: |
Brian Gough |

**Subject**: |
Re: [Bug-gsl] gsl_integration_qagiu failure |

**Date**: |
Fri, 27 Feb 2004 17:07:40 +0000 |

Manoj Rajagopalan writes:
>* The result of integration of the square of the radial component of *
>* the normalized hydrogenic bound state wave function (double *
>* gsl_sf_hydrogenicR_1(double Z, double r) from gsl_sf_coulomb.h) over *
>* range of r from 0 to INFINITY should be 1.0*
>* Using gsl_integration_qagiu to perform this semi-infinite integral *
>* yields the result 0.0 or core-dumps with an underflow. See file *
>* qagiu.txt (attached)*
Thanks for the email. In this case the library is reporting a
legitimate underflow when gsl_sf_hydrogenicR_1 is called with a very
large first argument.
By default there is an abort() for any underflow, since they could be
important in some circumstances. Use gsl_set_error_handler_off(); to
avoid seeing underflows.
Working in terms of r/a instead of a dimensionful r would help with
the scaling of the variable since the transformation of the infinite
integral to a finite range used by the QAGIU algorithm is not scale
free.
regards
--
Brian Gough