Re: Algorithm Analysis Course: Should I use Mathematica for projects?

*To*: mathgroup at smc.vnet.net*Subject*: [mg127296] Re: Algorithm Analysis Course: Should I use Mathematica for projects?*From*: Bill Rowe <readnews at sbcglobal.net>*Date*: Sat, 14 Jul 2012 01:32:09 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: mathgroup-newout@smc.vnet.net*Delivered-to*: mathgroup-newsend@smc.vnet.net

On 7/13/12 at 2:55 AM, fateman at cs.berkeley.edu (Richard Fateman) wrote: >An example. >Create 3 arrays. >A=Table[i,{i,0,100}]; >B=Table[i,{i,0,1000}]; >Q=Table[i,{i,0,10000}]; >Try updating the 50th element of each of these items, which look >like arrays in Mathematica. >Timing [A[[50]],{i,0,100000}] It is hard to understand what you mean here. If I paste what you posted into Mathematica I see the portion {i,0,100000} colored red. Not surprising since Timing accepts one argument not two. Perhaps you meant something like Timing[Do[a[[50]], {i, 100000}]] >Timing [B[[50]],{i,0,100000}] >Timing [Q[[50]],{i,0,100000}] >On my computer, these results take 0.266 seconds, 0.453 seconds, and >2.25 seconds, Assuming you did mean repeatedly reading the 50th element of each list, I cannot reproduce your results. I get In[1]:= a = Range[100]; b = Range[1000]; c = Range[10000]; In[4]:= Timing[Do[a[[50]], {i, 100000}]] Out[4]= {0.054508,Null} In[5]:= Timing[Do[b[[50]], {i, 100000}]] Out[5]= {0.055219,Null} In[6]:= Timing[Do[c[[50]], {i, 100000}]] Out[6]= {0.053313,Null} which indicates a constant access time. >Now, instead of creating these guys as what appears to be arrays, >one uses >A=Array[#&,100] >B=Array[#&,1000] >Q=Array[#&,10000] >How does that change the results? On my machine, not much In[8]:= a = Array[# &, 100]; b = Array[# &, 1000]; c = Array[# &, 10000]; In[11]:= Timing[Do[a[50], {i, 100000}]] Out[11]= {0.034209,Null} In[12]:= Timing[Do[b[50], {i, 100000}]] Out[12]= {0.032917,Null} In[13]:= Timing[Do[c[50], {i, 100000}]] Out[13]= {0.033273,Null}