Atomicity Post: 50813

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Top Forums Programming Atomicity Post 50813 by S.P.Prasad on Monday 3rd of May 2004 09:26:53 AM

05-03-2004

Registered User

First of all I would thank Driver for all the technical support and aid that he has provided.

Driver as you have stated that:

Quote:

lock(resources.semid);
if (data[1].used == 0 && data[2].used == 0) {
data[1].used = 1;
data[2].used = 1;
} else {
unlock(resources.semid);
/* Wait for 1 and 2 to become free */
}
unlock(resources.semid);

We have more than 10 process and in each process it has to LOCK or REL the LOCK for a specific array. One specific process cannot lock or release for more than one resource at a time. As per your pseudo-code then we need to have as many number of SEMAPHORES as there are number of arrays and LOCK / REL piece of code should be injected where locking and releasing of the resource comes into picture within the process. That would include a lot of re-work in the project. Will it be time efficient?

That is what I have posted the same in initial post.

Yes your pseudo-code would work fine if through out the processes we make a check that for a specific array the mapped SEMAPHORE key would lock or unlock the resource.

Thanks Driver, your solution is definitely a valuable one. I will build up a set of test executables implementing your pseudo-code.

Also please let me know if the pseudo-code I posted in my initial post is ok or not?

Thanks in advance.

Last edited by S.P.Prasad; 05-03-2004 at 10:34 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)