Re: Bug with Hypergeometric2F1?

• To: mathgroup at smc.vnet.net
• Subject: [mg99422] Re: [mg99384] Bug with Hypergeometric2F1?
• From: Bob Hanlon <hanlonr at cox.net>
• Date: Tue, 5 May 2009 05:43:41 -0400 (EDT)

```It is a numerical precision problem

vol1[n_, k_] = Sum[Binomial[n, i], {i, 0, k}]

2^n - Binomial[n, k + 1]*Hypergeometric2F1[1, k - n + 1, k + 2,
-1]

vol1 @@@ {{1000, 1}, {1000, 1.}, {1000., 1}, {1000., 1.}}

{1001, 5.28426328596665*^288, 5.28426328596665*^288,
5.28426328596665*^288}

Increase the numerical precision of the input

vol1 @@@ {{1000, 1}, {1000, 1.`400},
{1000.`400, 1}, {1000.`400, 1.`400}} // Round

{1001,1001,1001,1001}

Or change the function definition to force precision

vol1[n_, k_] := Sum[Binomial[Rationalize[n, 0], i],
{i, 0, Rationalize[k, 0]}]

vol1 @@@ {{1000, 1}, {1000, 1.}, {1000., 1}, {1000., 1.}}

{1001,1001,1001,1001}

Bob Hanlon

---- irchans <infinitgames at yahoo.com> wrote:

=============
When I run this code:

vol1[n_, k_] = Sum[ Binomial[n, i], {i, 0, k}]
vol1[1000, 1]
vol1[1000, 1.]

I get

Out[1] = 1001

Out[2] = 7.12935*10^288

I am running Mathematica 7.0.0 on windows 2000.  Does anyone else have
this problem?

```

• Prev by Date: Re: problems with DSolve
• Next by Date: Re: why does DownValues not return all downvalues for a
• Previous by thread: Re: Bug with Hypergeometric2F1?
• Next by thread: Re: Re: Bug with Hypergeometric2F1?