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