1 Commits (c01676e46d3be08c3c140361ef1f5884f47d3b3c)

Author	SHA1	Message	Date
kailiu	c01676e46d	Implement autovector ... Summary: A vector that leverages pre-allocated stack-based array to achieve better performance for array with small amount of items. Test Plan: Added tests for both correctness and performance Here is the performance benchmark between vector and autovector Please note that in the test "Creation and Insertion Test", the test case were designed with the motivation described below: * no element inserted: internal array of std::vector may not really get initialize. * one element inserted: internal array of std::vector must have initialized. * kSize elements inserted. This shows the most time we'll spend if we keep everything in stack. * 2 * kSize elements inserted. The internal vector of autovector must have been initialized. Note: kSize is the capacity of autovector ===================================================== Creation and Insertion Test ===================================================== created 100000 vectors: each was inserted with 0 elements total time elapsed: 128000 (ns) created 100000 autovectors: each was inserted with 0 elements total time elapsed: 3641000 (ns) created 100000 VectorWithReserveSizes: each was inserted with 0 elements total time elapsed: 9896000 (ns) ----------------------------------- created 100000 vectors: each was inserted with 1 elements total time elapsed: 11089000 (ns) created 100000 autovectors: each was inserted with 1 elements total time elapsed: 5008000 (ns) created 100000 VectorWithReserveSizes: each was inserted with 1 elements total time elapsed: 24271000 (ns) ----------------------------------- created 100000 vectors: each was inserted with 4 elements total time elapsed: 39369000 (ns) created 100000 autovectors: each was inserted with 4 elements total time elapsed: 10121000 (ns) created 100000 VectorWithReserveSizes: each was inserted with 4 elements total time elapsed: 28473000 (ns) ----------------------------------- created 100000 vectors: each was inserted with 8 elements total time elapsed: 75013000 (ns) created 100000 autovectors: each was inserted with 8 elements total time elapsed: 18237000 (ns) created 100000 VectorWithReserveSizes: each was inserted with 8 elements total time elapsed: 42464000 (ns) ----------------------------------- created 100000 vectors: each was inserted with 16 elements total time elapsed: 102319000 (ns) created 100000 autovectors: each was inserted with 16 elements total time elapsed: 76724000 (ns) created 100000 VectorWithReserveSizes: each was inserted with 16 elements total time elapsed: 68285000 (ns) ----------------------------------- ===================================================== Sequence Access Test ===================================================== performed 100000 sequence access against vector size: 4 total time elapsed: 198000 (ns) performed 100000 sequence access against autovector size: 4 total time elapsed: 306000 (ns) ----------------------------------- performed 100000 sequence access against vector size: 8 total time elapsed: 565000 (ns) performed 100000 sequence access against autovector size: 8 total time elapsed: 512000 (ns) ----------------------------------- performed 100000 sequence access against vector size: 16 total time elapsed: 1076000 (ns) performed 100000 sequence access against autovector size: 16 total time elapsed: 1070000 (ns) ----------------------------------- Reviewers: dhruba, haobo, sdong, chip Reviewed By: dhruba CC: leveldb Differential Revision: https://reviews.facebook.net/D14655	11 years ago