[Date Index] [Thread Index] [Author Index]

Re: Low precision exponentiation

• To: mathgroup at smc.vnet.net
• Subject: [mg129850] Re: Low precision exponentiation
• From: Bob Hanlon <hanlonr357 at gmail.com>
• Date: Mon, 18 Feb 2013 06:04:03 -0500 (EST)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com
• Delivered-to: l-mathgroup@wolfram.com
• Delivered-to: mathgroup-newout@smc.vnet.net
• Delivered-to: mathgroup-newsend@smc.vnet.net
• References: <20130217090833.8CF776937@smc.vnet.net>

To avoid using machine precision enter exact numbers (Rationalize).
Exact result:

Rationalize[2.5]^125

2350988701644575015937473074444491355637331113544175043017503412556834518909454345703125/42535295865117307932921825928971026432

To a specified precision

N[%, 25]

5.527147875260444560247265192192255725514240233239`25.*^49


Bob Hanlon


On Sun, Feb 17, 2013 at 4:08 AM, Blaise F Egan <blaise at blaisefegan.me.uk> wrote:
> I am trying to evaluate 2.5^125 to high precision.
>
> R gives 5.527147875260445183346e+49 as the answer but Mathematica with N[2.5^125,30] gives 5.52715*10^49 and says that is to machine precision.
>
> I am inexperienced at Mathematica. Am I doing something silly?
>
> Blaise
>

• References:
  • Low precision exponentiation
    • From: Blaise F Egan <blaise@blaisefegan.me.uk>