Path: utzoo!mnetor!uunet!husc6!mit-eddie!uw-beaver!tektronix!reed!langford
From: langford@reed.UUCP (Chris Langford)
Newsgroups: comp.lang.postscript
Subject: VM and operand stack limitations
Message-ID: <8483@reed.UUCP>
Date: 15 Mar 88 16:35:28 GMT
Organization: Reed College, Portland OR
Lines: 60
Keywords: virtual, memory, operand, LaserWriter

Hi there,
	I have been working on a little bit of PostScript code that prints
out digitized electrical signals.  We collect neurobiological data, and 
thus have to collect lots of data (14 k samples/sec for several 10s of
seconds at a time).

There are two problems I have:

1)  The operand stack will only hold 500 objects, so I am (I think)
forced to have 100s of K of data broken down into groups of 500.

2)  The virtual memory has only 174 K at most, and thus I must limit
the amount of data I can print per page to about 13K samples (about a
second worth of data).

I have been able to get our program to save data in nice bunchs of
450 (with brackets around it and everything), and do a restore before
I get a VM error, but it is still a real pain in the ass to print.

My questions are:

Is there any way to get the operand stack to accept a larger number of
objects, or bypass it altogether (I have not been able to get anything
else to work)?

Is there a way to get the LaserWriter to dump its font dictionarys,
and thus create more available memory?

Are there any other ways you can think of to get around this problem?

I know the serverdict password, so if it requires some monkey business,
I can handle it.  

I have simplified the routine,  but it
basically goes like this (if it helps):

     [array of 450 integers here]
     /data exch def
     0 data 0 get moveto
     0 2 data length 1 sub
          {
          data exch dup 
          /xval exch def
          get 
          xval exch lineto
          }
     for 
     stroke
  
I have 2 channels of data alternating, so I do the same procedure 
twice, but have the "for" loop begin with:

	0 1 data length 1 sub

to get the other half of the data printed out.

Thanks for any help.

Chris Langford
tektronix!reed!langford