icetStrategy(3)

NAME
icetStrategy -- set the strategy used to composite images.

Synopsis

#include <IceT.h>

void icetStrategy( | IceTEnum | 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, icetCompositeImage, or icetGLDrawFrame is called.

A strategy is chosen from one of the following provided enumerated values:

ICET_STRATEGY_SEQUENTIAL
     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 inefficient when compositing for more than one tile, but is recommended for the single tile case because it bypasses some of the communication necessary for the other multi-tile strategies.

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 multi-tile applications. (However, in the special case where only one tile is defined, the sequential strategy is probably better.)

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_SEQUENTIAL, 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.

Some of the strategies, namely ICET_STRATEGY_SEQUENTIAL and ICET_STRATEGY_REDUCE, use a sub-strategy that composites the image for a single tile. This single image strategy can also be specified with icetSingleImageStrategy.

Errors

ICET_INVALID_ENUM
     The strategy argument does not represent a valid strategy.

Warnings

None.

Bugs

None known.

Copyright
Copyright (C)2003 Sandia Corporation

Under the terms of Contract DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains certain rights in this software.

This source code is released under the New BSD License.

See Also

icetCompositeImage(3), icetDrawFrame(3), icetGetStrategyName(3), icetGLDrawFrame(3), icetSingleImageStrategy(3)