fix index format issue #4256

Job	Run time
pytorch_tutorial_build_worker (13, 15, linux.g5.4xlarge.nvidia.gpu)	27m 55s
pytorch_tutorial_build_worker (4, 15, linux.g5.4xlarge.nvidia.gpu)	35m 56s
pytorch_tutorial_build_worker (5, 15, linux.g5.4xlarge.nvidia.gpu)	22m 35s
pytorch_tutorial_build_worker (3, 15, linux.g5.4xlarge.nvidia.gpu)	21m 21s
pytorch_tutorial_build_worker (7, 15, linux.g5.4xlarge.nvidia.gpu)	26m 31s
pytorch_tutorial_build_worker (10, 15, linux.g5.4xlarge.nvidia.gpu)	17m 40s
pytorch_tutorial_build_worker (1, 15, linux.g5.12xlarge.nvidia.gpu)	16m 7s
pytorch_tutorial_build_worker (6, 15, linux.g5.4xlarge.nvidia.gpu)	23m 9s
pytorch_tutorial_build_worker (9, 15, linux.g5.4xlarge.nvidia.gpu)	17m 21s
pytorch_tutorial_build_worker (14, 15, linux.g5.4xlarge.nvidia.gpu)	24m 37s
pytorch_tutorial_build_worker (12, 15, linux.g5.4xlarge.nvidia.gpu)	19m 17s
pytorch_tutorial_build_worker (11, 15, linux.g5.4xlarge.nvidia.gpu)	15m 7s
pytorch_tutorial_build_worker (15, 15, linux.g5.4xlarge.nvidia.gpu)	27m 47s
pytorch_tutorial_build_worker (8, 15, linux.g5.4xlarge.nvidia.gpu)	15m 54s
pytorch_tutorial_build_worker (2, 15, linux.g5.4xlarge.nvidia.gpu)	33m 38s
pytorch_tutorial_build_manager	25m 42s
	6h 10m 37s

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