From: Yair Kurzion (yair++at++polygon.engr.sgi.com)
Date: 07/20/2001 10:22:48
Hello Todd !
A flux with PFFLUX_PUSH on always forces an evaluation of all engines
that it feeds upon the call to writeComplete. If PFFLUX_PUSH is off,
writeComplete marks all engines that read this fluxes as `srcChanged', and
returns.
When creating engine/flux chains, you can ``charge'' the cost of computing
the engine functions to either:
o The process writing the source fluxes that the engine reads.
o The process reading the destination fluxes that the engine computes.
In other words, if the source fluxes are written by a slow (asynchronous)
process like DBASE or COMPUTE, and the destination fluxes are read by any of
APP/CULL/DRAW, then you often want a writeComplete to trigger an engine
evaluation in the slow process. This way, when APP/CULL/DRAW try to read the
destination flux, they don't have to recompute the engine result.
So, if the source fluxes have PFFLUX_PUSH set, the engine evaluation happens at
writeComplete. Otherwise, if the destination flux has FF_ON_DEMAND set,
evaluation happens when you getCurData on the destination flux.
Can you use this info to design the flow of your engine/flux chain ?
-yair
> I am creating a chain of pfFlux's and pfEngine's, and I've found that
> pfFlux::writeComplete() does not return on the first pfFlux until all
> processing is complete. It seems like pfEngine's have a way around this
> issue because they finish processing in sequence.
>
> First, I create a pfFlux to start the chain with the following options:
> m_p_Fluxmem->setMode(PFFLUX_COPY_LAST_DATA, PF_ON);
> m_p_Fluxmem->setMode(PFFLUX_PUSH, PF_ON);
>
> Then I create a number of pfEngine's of type PFENG_USER_FUNCTION.
>
> So, a chain looks something like this:
> pfFlux1 -> pfEngine1 -> pfFlux2 -> pfEngine2 -> pfFlux3
>
> And here's the order in which things occur:
> 1. call getWritableData() on pfFlux1
> 2. write data, call writeComplete() on pfFlux1
> 3. pfEngine1 user function processes
> 4. pfEngine2 user function processes
> 5. writeComplete() on pfFlux1 returns
>
> My issue here is that I want to keep putting data into pfFlux1, but my
> update function that calls writeComplete() get stalled. In the final
> application, I will likely have multiple branches to the chain, and I
> need to put data into memory at the speed at which the fastest branch
> processes.
>
> Is there a way to perhaps fork the writeComplete() so that it doesn't
> slow things down? Or can I somehow start a chain with a pfEngine
> instead?
>
> Thanks,
> Todd
>
> --
> Todd J. Furlong
> MOTEK Motion Technology, Inc. voice 603.641.1300
> 360 Commercial St fax 603.641.8385
> Manchester, NH 03101 web http://www.e-motek.com
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--
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