Sum problem

*To*: mathgroup at smc.vnet.net*Subject*: [mg65285] Sum problem*From*: Majka Arkadiusz <Arkadiusz.Majka at telekomunikacja.pl>*Date*: Fri, 24 Mar 2006 00:59:42 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

Hi , I have a problem that drives me crazy. In order to sum a (long) list of elements (random numbers), say tab tab = Table[Random[], {10^7}]; we use In[3]:= Plus@@tab Out[3]= 4.999014220610286`*^6 ....but to check Sum we get In[6]:= Sum[tab[[i]],{i,1,Length[tab]}] Part specification K$30 is neither an integer nor a list of integers. There is no problem for Sum[tab[[i]], {i, 1, 10^6}] ...and for Sum[tab[[i]], {i, 1, 5*10^6}] So Sum is ok. for number of elements of tab less than certain number that is < Length[tab] I also tested recursion methods (doSum[k_]:=doSum[k]=doSum[k-1] ...... Etc) and got the same : fine but not for many elements (of course I set $RecursiveLimit and $IterationLimit as Infinity) I understand that to sum a list of elements we use Plus, Total etc but nevertheless I want understand what I explained above. Best, Arek