Re: slow 2d image generation

• To: Jim Cookas <James.M.Cookas@xxxxxxxx>
• Subject: Re: slow 2d image generation
• From: Tom Whittaker <tomw@xxxxxxxxxxxxx>
• Date: Tue, 06 Jan 2004 15:32:43 -0600

Hi Jim...

tom


Jim Cookas wrote:

tom, all

thanks a ton for the suggestion...it looks like this will be the method of 
choice for speeding up image display...i implemented the changes today, but i'm 
having a problem getting the image to display...i think it is a problem with my 
ascii file format...

i am using tab-spaced values...here is what test.tsv looks like:


(Down_Range,Cross_Range)->(RCS)
Down_Range[-755.383:755.383]    Cross_Range[-755.383:755.383]   RCS
[ 256 RCS values for Down_Range #0 ]
[ 256 RCS values for Down_Range #1 ]
.
.
.
[ 256 RCS values for Down_Range #255 ]


when i try to load this file into visad, i get these messages at the terminal:


Unit name problem:visad.data.units.ParseException: negative sign follows 
decimal point with -755.383:755.383
Unit name problem:visad.data.units.ParseException: negative sign follows 
decimal point with -755.383:755.383


any ideas on the problem?...thanks again!!

jc

-----Original Message-----
From: Tom Whittaker [mailto:tomw@xxxxxxxxxxxxx]
Sent: Monday, January 05, 2004 9:43 PM
To: Jim Cookas
Cc: Jim Koutsovasilis; visad@xxxxxxxxxxxxxxxx
Subject: Re: slow 2d image generation


Jim:

I believe that part of the slowness in "reading" is that the form of your data is producing an IrregularSet, which VisAD needs to "triagulate" when it does the display. If your data points are a "regular grid" (meaning, regular/constant spacing between data points) you can use the format:

Down_Range[-755.383:-200], Cross_Range[-755.838:-500], RCS

(where the '-200' and '-500' should be the actual ending values for the sample domain. If you do this, and then put all the RCS values (along the Cross_Range)for a single Down_Range on one input line. The text reader will compute the actual domain sampling coordinate for each "RCS" value. When you do this, the TextAdapter will make a Gridded2DSet for the sampling domain, and it is handled faster than the IrregularSet.

Of course, there will be some overhead for reading and decoding the text in either case, so I agree with JimK -- you may want to create your own reader.

tom

--
Tom Whittaker (tomw@xxxxxxxxxxxxx)
University of Wisconsin-Madison
Space Science and Engineering Center
Cooperative Institute for Meteorological Satellite Studies
Phone/VoiceMail: 608.262.2759

• References:
  • RE: slow 2d image generation
    • From: Jim Cookas