Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

Fix a bug in OverestimateReshardingCost, which failed to take into account the fact that a replicated strategy is also a "tile maximal" strategy. #17837

Merged
merged 1 commit into from
Oct 2, 2024
Merged

Fix a bug in OverestimateReshardingCost, which failed to take into account the fact that a replicated strategy is also a "tile maximal" strategy. #17837

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
16 changes: 8 additions & 8 deletions xla/hlo/experimental/auto_sharding/cluster_environment.cc
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,7 @@ limitations under the License.
#include "absl/container/flat_hash_map.h"
#include "absl/log/check.h"
#include "absl/types/span.h"
#include "xla/hlo/experimental/auto_sharding/auto_sharding_device_mesh.h"
#include "xla/hlo/experimental/auto_sharding/auto_sharding_strategy.h"
#include "xla/hlo/experimental/auto_sharding/auto_sharding_util.h"
#include "xla/hlo/ir/hlo_sharding.h"
Expand Down Expand Up @@ -162,7 +163,7 @@ double ClusterEnvironment::ReshardingCostMixedMeshShape(
}
if (IsSubset((*dst_tensor_dim_to_mesh_axis)[i],
(*src_tensor_dim_to_mesh_axis)[i])) {
// do nothing; the src is sharded more than the dest
// do nothing; the dst is sharded more than the src
continue;
}
if (!IsSubset((*src_tensor_dim_to_mesh_axis)[i],
Expand Down Expand Up @@ -231,17 +232,16 @@ double ClusterEnvironment::CollectivePermuteCost(
// Overestimate the cost of replicating a tensor by decomposing the resharding
// operation as an all-gather on all mesh dimensions.
double ClusterEnvironment::OverestimateReplicationCost(
const Shape& shape, const HloSharding& src_spec,
const Shape& shape, const HloSharding& src_sharding,
const DeviceMesh& device_mesh) const {
if (src_spec.IsTileMaximal() || src_spec.IsManual()) {
// TODO(b/238210866) Do not use kInfinityCost.
return kInfinityCost;
if (src_sharding.IsReplicated()) {
return 0;
}
int64_t bytes_moved = ByteSizeOfShapeWithSharding(shape, src_spec);
int64_t bytes_moved = ByteSizeOfShapeWithSharding(shape, src_sharding);
double cost = 0.0;
for (size_t i = 0; i < device_mesh.num_dimensions(); ++i) {
auto this_cost = this->AllGatherCost(bytes_moved, i);
cost += this_cost;
cost += src_sharding.IsTileMaximal() ? this->AllReduceCost(bytes_moved, i)
: this->AllGatherCost(bytes_moved, i);
bytes_moved *= device_mesh.dimensions()[i];
}
return cost;
Expand Down
Loading