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Niels Lohmann
16ed40b2d4
enter_cbor_array and enter_msgpack_array called the out-of-line scalar run for every non-empty array. When the array's element is an object or an array, as on every level of [[...]] or the single ring of a GeoJSON polygon, the call reads nothing; it made 1,000 arrays nested in each other cost 4 % more instructions (GCC 13) and up to 8 % more time (Apple clang) than without the run. #5975 had fixed that with an inline pre-check, which was later dropped after measuring canada only. The run is now entered only for arrays of two or more elements: the same comparison as before, so no other row changes. Arrays of one scalar, which the run read faster, now take the general path; they are rare in documents (one in citm_catalog, none in twitter or canada). The new benchmark FromBinaryShape/singles measures them, next to FromBinaryShape/nested. Instructions per repetition, new/old, GCC 13 callgrind: nested arrays 0.973 (CBOR) and 0.971 (MessagePack), arrays of one scalar 1.037 and 1.021, every other row within 0.15 %. Signed-off-by: Niels Lohmann <mail@nlohmann.me>