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Fix for finding the recomputing symbols in rematerialization #700
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IvanYashchuk
reviewed
Jul 3, 2024
IvanYashchuk
reviewed
Jul 3, 2024
IvanYashchuk
reviewed
Jul 3, 2024
A minimal example reproducing the problem and a test is required here. |
kiya00
changed the title
Remove duplicated names in rematerialization (#665)
Fix for finding the recomputing symbols in rematerialization
Jul 5, 2024
Test results on 2nodes(8 H100):
|
IvanYashchuk
approved these changes
Jul 5, 2024
t-vi
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Jul 5, 2024
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Thank you @kiya00 @IvanYashchuk
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To Reproduce
The original bug appears when running with 2 nodes(8 GPUs each), another reproduction is using one node with 7 GPUs.
torchrun --nnodes=1 --nproc-per-node=7 ../thunder/benchmarks/benchmark_litgpt.py --model_name dolly-v2-3b --compile thunder_inductor_cat_cudnn --distributed_mode fsdp --shard_mode zero2
set
n_layers=1
will give a shorter traceThe reason why it appears in such specific setting is because when sharding needs padding, it has additional slice operator.
To reproduce in one process fsdp:
Apply patch:
Run
torchrun --nnodes=1 --nproc-per-node=1 ../thunder/benchmarks/benchmark_litgpt.py --model_name dolly-v2-3b --compile thunder_inductor_cat_cudnn --distributed_mode fsdp --shard_mode zero2
Analysis
In rematerialization it finds the symbols that produce the
rematerialized_inputs
based on a combination of producer/consumer subsymbols(thetrace
below), but they could have the same subsymbols in producer and consumer:lightning-thunder/thunder/core/rematerialization.py
Line 166 in a1bbce6
lightning-thunder/thunder/core/rematerialization.py
Line 168 in a1bbce6
Here is an example of that in the bug:
(this is when remat applied on joint trace, I think the same subsymbols exist in both consumer/producer is because the previous remats happened in
fusion_pass
copy the samerecomputing_symbols
into bothnew_consumer
)Since the
rematerialized_inputs
comes from the inputs of consumer, so we can find therecomputing_symbols
from the subsymbols in producer.Fixes #665