Re: Why Does Repeated Dot Product Take So Long?
- To: mathgroup at smc.vnet.net
- Subject: [mg67950] Re: [mg67938] Why Does Repeated Dot Product Take So Long?
- From: Sseziwa Mukasa <mukasa at jeol.com>
- Date: Tue, 18 Jul 2006 05:50:35 -0400 (EDT)
- References: <200607171051.GAA02347@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
What is in x and y?
Using matrices of machine precision real numbers it take about 3ms on
a dual 2.5GHz G5 for me.
Regards,
Ssezi
On Jul 17, 2006, at 6:51 AM, Gregory Lypny wrote:
> Hello Everyone,
>
> x and y are both 2000 x 3 matrices. I wanted to created a 2000 x 1
> vector with each element equal to the dot product of the
> corresponding rows of x and y. So I tried this:
>
> Table[x[[i]].y[[i]], {i, 1, 2000}]
>
> It took more than two and a half minutes on my iBook G4. Is that
> normal? I've done seemingly more demanding computations in Do loops
> and Tables that are completed in a split second. Am I doing
> something wrong with this one?
>
> Regards,
>
> Gregory
>
- References:
- Why Does Repeated Dot Product Take So Long?
- From: Gregory Lypny <gregory.lypny@videotron.ca>
- Why Does Repeated Dot Product Take So Long?