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@mratsim mratsim released this 04 Apr 19:15
· 56 commits to master since this release
v0.4.0
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mratsim Mamy Ratsimbazafy
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Learn about vigilant mode.

Compatibility

Weave now targets Nim 1.2.0 instead of devel. This is the first Nim release
that supports all requirements of Weave.

Features

Weave now provides an experimental "dataflow parallelism" mode.
Dataflow parallelism is also known under the following names:

  • Graph parallelism
  • Stream parallelism
  • Pipeline parallelism
  • Data-driven parallelism

Concretely this allows delaying tasks until a condition is met.
This condition is called Pledge.
Programs can now create a "computation graph"
or a pipeline of tasks ahead of time that depends on one or more Pledge.

For example a game engine might want to associate a pipeline of transformations
to each frame and once the frame prerequisites are met, set the Pledge to fulfilled.

The Pledge can be combined with parallel loops and programs can wait on specific
iterations or even iteration ranges for example to implement parallel video processing
as soon as a subset of the frame is ready instead of waiting for the whole frame.
This exposes significantly more parallelism opportunities.

Dataflow parallelism cannot be used with the C++ backend at the moment.

Weave now provides the 3 main parallelism models:

  • Task Parallelism (spawn/sync)
  • Data Parallelism (parallel for loop)
  • Dataflow Parallelism (delayed tasks)

Performance

Weave scalability has been carefully measured and improved.

On matrix multiplication, the traditional benchmark to classify the top 500 supercomputers of the world, Weave speedup on an 18-core CPU is 17.5x while the state-of-the-art Intel implementation using OpenMP allows 15.5x-16x speedup.

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