Can the PEX Renderer be interrupted?

[Greg Kohring]

Hi,

I've a program which needs to render several hundred thousand
polygons. I first store the information in a PEXStructure and
then issure PEXExecuteStructure. Building the structure takes
less than a second, but rendering can take up to a minute and
during this time the X-server is completely locked-up.
(We're running SUN SunOS Release 5.4 on a Sparc-10 with PEX 5.1.)

Question: is it possible to interrupt the Renderer?

I assume the answere is no, because the X-server does not
respond until rendering is done. Does anyone have a good
idea how to get around this problem?

Thanks for any advice!

-- Greg Kohring

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G.A. Kohring | fax : [49]-[2461]-612430
Forschungszentrum Juelich GmbH | phone : [49]-[2461]-616761
D-52425 Juelich, Germany | e-mail: g.ko...@kfa-juelich.de
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[Karl Schultz]

In article <1995May3...@hlrz25.hlrz.kfa-juelich.de>, g.ko...@kfa-juelich.de (Greg Kohring) writes:
> Hi,
>
> I've a program which needs to render several hundred thousand
> polygons. I first store the information in a PEXStructure and
> then issure PEXExecuteStructure. Building the structure takes
> less than a second, but rendering can take up to a minute and
> during this time the X-server is completely locked-up.
> (We're running SUN SunOS Release 5.4 on a Sparc-10 with PEX 5.1.)
>
> Question: is it possible to interrupt the Renderer?

Not during the processing of a single request.

Some implementations of X/PEX servers can process
PEX and X requests at the same time to get around the problem
you describe. They do this by occasionally checking the
X request queue during a long rendering operation and
temporarily suspending PEX rendering while processing
X requests for other clients.
This can sometimes let other clients operate
while processing a lengthy PEX request.

Some other implementations run PEX in another process, which lets
the X server keep running. Of course, there are quite a few
timing and synchronization issues.

The advent of threaded X servers will improve the situation
in a more unified manner.

> I assume the answere is no, because the X-server does not
> respond until rendering is done. Does anyone have a good
> idea how to get around this problem?

Instead of using a single atomic request to draw the
entire structure, try drawing it in pieces.
Suppose you have 1000 elements and decide to render 100 at a time.

RenderElements(struct,1,100)
RenderElements(struct,101,200)
RenderElements(struct,201,300)
....
RenderElements(struct,901,1000)

Depending on the dispatching policy of the X server (I
forget the rules there), you may need an XSync between
each call.

Anyway, this should give the server at least a chance
to process requests for other clients while drawing
your picture.

Hope this helps.