This document is relevant for: Inf1, Inf2, Trn1, Trn2, Trn3

NCC_EVRF024#

Error message: The output tensor size limit of 4GB was exceeded.

There are two potential ways to fix this issue:

  1. Simply reduce the batch/tensor size if possible

  2. Utilize tensor parallelism via neuronx-distributed

Short snippet of tensor parallelism:

class ParallelSelfAttention(transformers.models.bert.modeling_bert.BertSelfAttention):
    def __init__(self, config, position_embedding_type=None):
        super().__init__(config, position_embedding_type)

        self.query = ColumnParallelLinear(config.hidden_size,
                                        self.all_head_size,
                                        gather_output=False)
        self.key = ColumnParallelLinear(config.hidden_size,
                                        self.all_head_size,
                                        gather_output=False)
        self.value = ColumnParallelLinear(config.hidden_size,
                                        self.all_head_size,
                                        gather_output=False)
        # Since we shard the number of attention heads across tensor parallel
        # ranks, each rank would have a subset of heads, hence, we update
        # the num_attention_heads here.
        tp_size = parallel_state.get_tensor_parallel_size()
        self.num_attention_heads = self.num_attention_heads // tp_size
        self.all_head_size = self.all_head_size // tp_size

For more information: https://awsdocs-neuron.readthedocs-hosted.com/en/latest/libraries/neuronx-distributed/activation_memory_reduction.html

This document is relevant for: Inf1, Inf2, Trn1, Trn2, Trn3