CALCULATION TIME
- To: mathgroup at smc.vnet.net
- Subject: [mg21418] CALCULATION TIME
- From: Blimbaum Jerry DLPC <BlimbaumJE at ncsc.navy.mil>
- Date: Thu, 6 Jan 2000 01:46:34 -0500 (EST)
- Sender: owner-wri-mathgroup at wolfram.com
I have some code performing (roughly) the following Do Loops:
Do[.........
Do[x[[m,n+1]] = x[[m,n]] + B* y[[n+m-1]]*e[[n]]
----------------------------------------------,
eps+Sum[y[[n-q]]^2,{q,0,M-1}]
{m,M} ],
{n,M,Length[y]}]
where y, e are lists (y is data that contains about 30000 elements),
etc. Running a data set takes about 10.5 secs. I wanted to shorten the
time but couldnt figure out how to write it either in Nest or Compile form
so I went thru it piece meal to see if I could find a culprit and from this
I noticed if I replace the Sum term in the denominator by a number, lets say
1, and then perform the calculations it only takes about 2.5 seconds! I
did a sample Sum[expr^2] with a similar Do loop separately and it takes no
time at all.
What is wrong?
thanks. Jerry Blimbaum NSWC Panama City, Fl