[hybrid] remove scale op in insert_scale_loss_grad_ops#35775
[hybrid] remove scale op in insert_scale_loss_grad_ops#35775wangxicoding merged 2 commits intoPaddlePaddle:developfrom
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wangxicoding
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JZ-LIANG,
fuyinno4,
gongweibao and
sandyhouse
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LGTM for code modification, but I think after this modification, the program description maybe confusing for others.
Might need a comment to notify the later maintainer that the start point of gradient backward would change according to the DataParallel and ShardingParallel degree. |
OK，add in next PR. |
| "loss_grad_op must be fill_constant op, " \ | ||
| "but this op is {}".format(op.type) | ||
| assert op.has_attr('value') | ||
| loss_scale = float(op.attr('value')) |
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Mind the potential precision loss here. fill_constant op will cast the value into fp32 and then save as string into its OpDesc. reload & reset this value might cause precision loss when the denominator is odd （3，7， 11， etc）
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loss_grad_op(that is fill_constant) use value instead of str_value, which AttrType is float. value will be saved with float32 in protobuf. If we encount precision problem, I this this must be caused by float AttrType, and I think double AttrType is better, which framework does not provide.
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the type of op.attr('value') is already float64 in python, add float(op.attr('value')) is only for explicit.
3 participants
PR types
Performance optimization
PR changes
Others
Describe
移除insert_scale_loss_grad_ops中插入的scale op，直接取出loss_grad_op也即fill_constant中的value值修改，可减少插入scale op的个数。理论可以提高一小丢丢丢性能。
测试
Ernei3.0，base模型
后续优化TODO
pipeline里面可以将loss_grad_op放到LRSchedule里，一个step只执行一次，而非每个micro-step都执行。或者更激进点，设置为persistable，在startup_program里面初始化，一次训练只执行一次。