Limit cast fanout #1196
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Limit cast fanout #1196
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Summary: ActorMesh's shape might have large extents on some dimensions. Those dimensions would cause large fanout in our comm actor implementation. To avoid that, we reshape it by increasing dimensionality and limiting the extent of each dimension. Note: the reshape is only visibility to the internal algorithom. Theshape that user sees maintains intact. For example, a typical shape is [hosts=1024, gpus=8]. By using limit 8, it becomes [8, 8, 8, 2, 8] during casting. In other words, it adds 3 extra layers to the comm actor tree, while keeping the fanout in each layer at 8 or smaller. The limit for cast fanouts will be configured by the key `CASTING_FANOUT_SIZE` which is currently set to 0 as default disabling the feature. Differential Revision: D82320948
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Summary: ActorMesh's shape might have large extents on some dimensions. Those dimensions would cause large fanout in our comm actor implementation. To avoid that, we reshape it by increasing dimensionality and limiting the extent of each dimension. Note: the reshape is only visibility to the internal algorithom. Theshape that user sees maintains intact. For example, a typical shape is [hosts=1024, gpus=8]. By using limit 8, it becomes [8, 8, 8, 2, 8] during casting. In other words, it adds 3 extra layers to the comm actor tree, while keeping the fanout in each layer at 8 or smaller. The limit for cast fanouts will be configured by the key `CASTING_FANOUT_SIZE` which is currently set to 0 as default disabling the feature. Differential Revision: D82320948
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Summary: ActorMesh's shape might have large extents on some dimensions. Those dimensions would cause large fanout in our comm actor implementation. To avoid that, we reshape it by increasing dimensionality and limiting the extent of each dimension. Note: the reshape is only visibility to the internal algorithom. Theshape that user sees maintains intact. For example, a typical shape is [hosts=1024, gpus=8]. By using limit 8, it becomes [8, 8, 8, 2, 8] during casting. In other words, it adds 3 extra layers to the comm actor tree, while keeping the fanout in each layer at 8 or smaller. The limit for cast fanouts will be configured by the key `CASTING_FANOUT_SIZE` which is currently set to 0 as default disabling the feature. Differential Revision: D82320948
thomasywang
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Sep 19, 2025
Summary: ActorMesh's shape might have large extents on some dimensions. Those dimensions would cause large fanout in our comm actor implementation. To avoid that, we reshape it by increasing dimensionality and limiting the extent of each dimension. Note: the reshape is only visibility to the internal algorithom. Theshape that user sees maintains intact. For example, a typical shape is [hosts=1024, gpus=8]. By using limit 8, it becomes [8, 8, 8, 2, 8] during casting. In other words, it adds 3 extra layers to the comm actor tree, while keeping the fanout in each layer at 8 or smaller. The limit for cast fanouts will be configured by the key `CASTING_FANOUT_SIZE` which is currently set to 0 as default disabling the feature. Differential Revision: D82320948
Summary: ActorMesh's shape might have large extents on some dimensions. Those dimensions would cause large fanout in our comm actor implementation. To avoid that, we reshape it by increasing dimensionality and limiting the extent of each dimension. Note: the reshape is only visibility to the internal algorithom. Theshape that user sees maintains intact. For example, a typical shape is [hosts=1024, gpus=8]. By using limit 8, it becomes [8, 8, 8, 2, 8] during casting. In other words, it adds 3 extra layers to the comm actor tree, while keeping the fanout in each layer at 8 or smaller. The limit for cast fanouts will be configured by the key `CASTING_FANOUT_SIZE` which is currently set to 0 as default disabling the feature. Differential Revision: D82320948
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Summary: ActorMesh's shape might have large extents on some dimensions. Those dimensions would cause large fanout in our comm actor implementation. To avoid that, we reshape it by increasing dimensionality and limiting the extent of each dimension. Note: the reshape is only visibility to the internal algorithom. Theshape that user sees maintains intact. For example, a typical shape is [hosts=1024, gpus=8]. By using limit 8, it becomes [8, 8, 8, 2, 8] during casting. In other words, it adds 3 extra layers to the comm actor tree, while keeping the fanout in each layer at 8 or smaller. The limit for cast fanouts will be configured by the key `CASTING_FANOUT_SIZE` which is currently set to 0 as default disabling the feature. Differential Revision: D82320948
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Summary:
ActorMesh's shape might have large extents on some dimensions. Those dimensions would cause large fanout in our comm actor
implementation. To avoid that, we reshape it by increasing dimensionality and limiting the extent of each dimension. Note: the reshape is only visibility to the internal algorithom. Theshape that user sees maintains intact.
For example, a typical shape is [hosts=1024, gpus=8]. By using limit 8, it becomes [8, 8, 8, 2, 8] during casting. In other words, it adds 3 extra layers to the comm actor tree, while keeping the fanout in each layer at 8 or smaller.
The limit for cast fanouts will be configured by the key
CASTING_FANOUT_SIZEwhich is currently set to 0 as default disabling the feature.Differential Revision: D82320948