Add MultiTensorApply to calculate L2-Norm in DistributedFusedLamb optimizer #39900
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PR types
Performance optimization
PR changes
OPs
Describe
Use
MultiTensorApplyto improve the L2-Norm calculation inDistributedFusedLamboptimizer.优化前，
DistributedFusedLamb在计算Parameter L2-Norm和Trust Ratio Div L2-Norm的时候调用的cub::DeviceSegmentedReduce，改用MultiTensorApply的方式，并优化每个launch kernel时的最大Tensor数量、chunk数量等参数。BERT Large（batch_size = 56, max_seq_len = 512, pure_fp16）:
cub::DeviceSegmentedReduce）MaxTensorNumPerLaunch=110，MaxChunkNumPerLaunch=320MaxTensorNumPerLaunch=110，MaxChunkNumPerLaunch=320（对齐NV配置），优于NV 0.7%-2.2%，基本可以认为是持平。相比Paddle Baseline提升约95%。MaxTensorNumPerLaunch=50，MaxChunkNumPerLaunch=680，优于NV 14%。相比Paddle Baseline提升约96%。