fix loss performance (#1622) #2649

Job	Run time
build-and-test-cpp-aarch64 (openblas)	4m 20s
build-python-wheels (ubuntu-20.04, auto64)	26m 48s
build-and-push-docker-images	22m 19s
build-and-test-cpp-x86_64 (ubuntu-20.04, mkl)	5m 22s
build-python-wheels (macos-11, auto64)	36m 23s
build-and-test-cpp-x86_64 (ubuntu-20.04, dnnl)	4m 59s
build-python-wheels (windows-2019, auto64)	43m 47s
build-python-wheels (ubuntu-20.04, aarch64)	1h 14m 40s
check-python-style	8s
build-python-wheels (macos-11, arm64)	11m 11s
build-and-test-cpp-x86_64 (macos-11, mkl)	9m 51s
build-and-test-cpp-x86_64 (macos-11, dnnl)	9m 15s
build-and-deploy-docs	42s
test-python-wheels (ubuntu-20.04)	9m 49s
test-python-wheels (macos-11)	4m 57s
test-python-wheels (windows-2019)	4m 4s
publish-python-wheels-on-pypi	0s
	4h 28m 35s

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