Atomicity Post: 50804

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Top Forums Programming Atomicity Post 50804 by S.P.Prasad on Monday 3rd of May 2004 06:56:38 AM

05-03-2004

Registered User

First of all I would like to state that the pseudo-code I have written in my initial post needs modification. Instead of writing LOCK () and REL() as two separate functions, it would be only one subroutine LOCK_REL() implementing the pseudo-code.

Quote:

How are the variables shared - using shared memory?

Yes. This concept is already implemented in the project. All I need to is add up the required variables.

Quote:

No, you can also use a single lock for all resources, so that you might get heavy lock contention but still permit multiple processes to operate independently.

I studied the pseudo-code but that's what exactly we do not want. For example there are 10 process. Assume 2 different process would like to implement LOCK on the array and while 3 different process tries to REL the LOCK on the same array. Only one of the process should succeed for a specific array operation.

Further more of the remaining 5, 3 different process are trying to implement LOCK on 3 different arrays and 2 are REL two separate arrays, then they very well should. I mean they should not wait other wise timing would become a major issue i.e. time to process one transaction would increase.

Here's a sample view of what I would like to implement atomically:

Process'xx'1'xxxxx'2'xxxxx'3'xxxx'4'xxxxx'5'xxxxx'6'
Array'xxxx'A'xxxxx'B'xxxxx'C'xxxx'D'xxxxx'E'xxxxx'F'

xxxxxxxx ..... xxxx..... xx..... xxxx..... xxx......xxx.........
xxxxxxxxL(D)xxxxL(D)xxR(D)xxxxL(E)xxxR(F)xxxL(A)
xxxxxxxx ..... xxxx..... xx..... xxxx..... xxx......xxx.........

Where L stands for LOCK and R stands for REL the lock on array passed as arguments and value at array index 1 states whether array is locked ( value 1 ) or unlock ( value 0 ) . Please ignore the x's as I have put it for alignment purpose

I hope that I am clear in my requirement.

Thanks in advance.

Last edited by S.P.Prasad; 05-03-2004 at 09:55 AM..

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ppmtosixel

ppmtosixel(1)						      General Commands Manual						     ppmtosixel(1)

NAME

       ppmtosixel - convert a portable pixmap into DEC sixel format

SYNOPSIS

       ppmtosixel [-raw] [-margin] [ppmfile]

DESCRIPTION

       Reads  a  portable  pixmap  as input.  Produces sixel commands (SIX) as output.	The output is formatted for color printing, e.g. for a DEC
       LJ250 color inkjet printer.

       If RGB values from the PPM file do not have maxval=100, the RGB values are rescaled.  A printer control header and a color assignment table
       begin the SIX file.  Image data is written in a compressed format by default.  A printer control footer ends the image file.

OPTIONS

       -raw   If  specified,  each  pixel  will  be explicitly described in the image file.  If -raw is not specified, output will default to com-
	      pressed format in which identical adjacent pixels are replaced by "repeat pixel" commands.  A raw file is often an order	of  magni-
	      tude larger than a compressed file and prints much slower.

       -margin
	      If  -margin  is not specified, the image will be start at the left margin (of the window, paper, or whatever).  If -margin is speci-
	      fied, a 1.5 inch left margin will offset the image.

PRINTING

       Generally, sixel files must reach the printer unfiltered.  Use the lpr -x option or cat filename > /dev/tty0?.

BUGS

       Upon rescaling, truncation of the least significant bits of RGB values may result in poor color conversion.  If the original PPM maxval was
       greater	than  100,  rescaling  also reduces the image depth.  While the actual RGB values from the ppm file are more or less retained, the
       color palette of the LJ250 may not match the colors on your screen.  This seems to be a printer limitation.

SEE ALSO

       ppm(5)

AUTHOR

       Copyright (C) 1991 by Rick Vinci.

								   26 April 1991						     ppmtosixel(1)