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icetStrategy

NAME

icetStrategy -- set the strategy used to composite images.

Synopsis

#include <GL/ice-t.h>

void icetStrategy(

IceTStrategy

strategy );

Description

The IceT API comes packaged with several algorithms for compositing images. The algorithm to use is determined by selecting a strategy. The strategy is selected with icetStrategy. A strategy must be selected before icetDrawFrame is called.

The strategy is of type IceTStrategy. This is an opaque type. There are no conventions to create or change an IceTStrategy, but there are several predefined strategies to select from. They are:

ICET_STRATEGY_SERIAL

 Basically applies a ``traditional''  single tile composition (such as binary swap) to each tile in the order they were defined. Because each process must take part in the composition of each tile regardless of whether they draw into it, this strategy is usually very inefficient when compositing for more than tile. It is provided mostly for comparative purposes.

ICET_STRATEGY_DIRECT

 As each process renders an image  for a tile, that image is sent directly to the process that will display that tile. This usually results in a few processes receiving and processing the majority of the data, and is therefore usually an inefficient strategy.

ICET_STRATEGY_SPLIT

 Like ICET_STRATEGY_DIRECT, except that the tiles are split up, and each process is assigned a piece of a tile in such a way that each process receives and handles about the same amount of data. This strategy is often very efficient, but due to the large amount of messages passed, it has not proven to be very scalable or robust.

ICET_STRATEGY_REDUCE

 A two phase algorithm. In the  first phase, tile images are redistributed such that each process has one image for one tile. In the second phase, a ``traditional'' single tile composition is performed for each tile. Since each process contains an image for only one tile, all these compositions may happen simultaneously. This is a well rounded strategy that seems to perform well in a wide variety of applications.

ICET_STRATEGY_VTREE

 An extension to the binary tree  algorithm for image composition. Sets up a `virtual' composition tree for each tile image. Processes that belong to multiple trees (because they render to more than one tile) are allowed to float between trees. This strategy is not quite as well load balanced as ICET_STRATEGY_REDUCE or ICET_STRATEGY_SPLIT, but has very well behaved network communication.

Not all of the strategies support ordered image composition. ICET_STRATEGY_SERIAL, ICET_STRATEGY_DIRECT, and ICET_STRATEGY_REDUCE do support ordered image composition. ICET_STRATEGY_SPLIT and ICET_STRATEGY_VTREE do not support ordered image composition and will ignore ICET_ORDERED_COMPOSITE if it is enabled.

Errors

None.

Warnings

None.

Bugs

Use the ICET_STRATEGY_SPLIT strategy with care. It has proven to be unreliable on several high-speed interconnects. Avoid using it at all in a production application.

Copyright

Copyright (C)2003 Sandia Corporation

Under the terms of Contract DE-AC04-94AL85000, there is a non-exclusive license for use of this work by or on behalf of the U.S. Government. Redistribution and use in source and binary forms, with or without modification, are permitted provided that this Notice and any statement of authorship are reproduced on all copies.

See Also

icetDrawFrame(3), icetGetStrategyName(3)