Re: Challenge: Fastest method to convert positive integers to 1 in a long list
- To: mathgroup at smc.vnet.net
- Subject: [mg52195] Re: Challenge: Fastest method to convert positive integers to 1 in a long list
- From: Peter Pein <petsie at arcor.de>
- Date: Sun, 14 Nov 2004 04:31:00 -0500 (EST)
- References: <cn4m4e$19p$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Carl K. Woll wrote:
> Hi all,
>
> Inspired by the recent thread on counting runs, I have the following
> challenge. Come up with a method to convert all the positive integers in a
> long sequence of nonnegative integers to 1, so that the sequence consists of
> only 0s and 1s. Let the sequence be given by
>
> seq = Table[Random[Integer, 10], {10^6}];
>
> Then, one technique is
>
> newseq = 1+Quotient[#,#+1,1]&@seq;
>
> Can anyone do better?
>
> Carl Woll
>
>
Sign[.] is simpler, isn't it?
In[1]:= seq = Table[Random[Integer, 10], {10^6}];
In[2]:= t1 = First@Timing[newseq1 = 1 + Quotient[#, # + 1, 1] &@seq;]
Out[2]= 0.671 Second
In[3]:= t2 = First@Timing[newseq2 = Sign@seq;]
Out[3]= 0.12 Second
In[4]:= newseq1 == newseq2
t1/t2
Out[4]= True
Out[5]= 5.59167
..it is :-)
--
Peter Pein
Berlin