Re: Bug in SymbolicSum, or am I just stupid?
- To: mathgroup at smc.vnet.net
- Subject: [mg5624] Re: [mg5593] Bug in SymbolicSum, or am I just stupid?
- From: Sherman Reed <Sherman.Reed at worldnet.att.net>
- Date: Wed, 1 Jan 1997 21:04:54 -0500
- Sender: owner-wri-mathgroup at wolfram.com
At 06:59 AM 12/27/96 +0000, you wrote:
>I'm wondering if I'm just doing something really dumb, or if there
>is some profound reason why Mathematica 2.2 seems to be finding different
>symbolic infinite sumations for the same expression:
>
>
>
>Mathematica 2.2 for SPARC
>Copyright 1988-94 Wolfram Research, Inc.
> -- Terminal graphics initialized --
>
>In[1]:= <<Algebra`SymbolicSum`
>
>In[2]:= ?SymbolicSum
>SymbolicSum[f, {i, imin, imax}] attempts to find the value of Sum[f, {i, imin,
> imax} ] for symbolic imin,imax. SymbolicSum[f, {i, imax}] evaluates the sum
> of f with i running from 1 to imax.
>
>In[2]:= Simplify[(2)( 1/(2^n ) - ((n+1)/2)(1/(2^n))] (* expression 1 *)
>
> 3 - n
>Out[2]= -----
> n
> 2 2
>
>In[3]:= Simplify[(2 - (n+1)/2) (1/(2^n))] (* expression 2--should be same *)
>
> 3 - n
>Out[3]= -----
> n
> 2 2
>
>In[4]:= SymbolicSum[(2)( 1/(2^n) ) - ((n+1)/2)(1/(2^n)),{n,1,Infinity}] (*1*)
>
> 1
>Out[4]= -
> 2
>
>In[5]:= SymbolicSum[(2 - (n+1)/2) (1/(2^n)),{n,1,Infinity}] (*2*)
>
> 3
>Out[5]= -(-)
> 4
>
>In[6]:= SymbolicSum[Out[3],{n,1,Infinity}] (* simplified *)
>
> 3
>Out[6]= -(-)
> 4
>
>
>Thanks very much anyone. Sorry if this is a FAQ or obnoxious newbie question.
>
>Sean Luke
>U Maryland at College Park, very late a night
>seanl at cs.umd.edu
>
>
Sean,
I was able to duplicate your results on 2.2.3 under Win95, which are wrong.
Using 3.0, where SymbolicSum has apparently been redone, is called simply
SUM, and is autoloaded, I got the correct answers.
looks like a bug in 2.2.2 and 2.2.3
sherman c. reed