[GitHub] [arrow] pitrou commented on pull request #7901: ARROW-9543: [C++] Simplify parsing/formatting utilities

[GitBox <gi...@apache.org>]

pitrou commented on pull request #7901:
URL: https://github.com/apache/arrow/pull/7901#issuecomment-669219582


   It seems that micro-benchmark performance is regressing with this PR, at least here (clang 9.0, AMD Ryzen):
   * before:
   ```
   IntegerParsing<Int8Type>                        2396 ns         2396 ns       292824 items_per_second=417.353M/s
   IntegerParsing<Int16Type>                       4499 ns         4499 ns       155249 items_per_second=222.277M/s
   IntegerParsing<Int32Type>                       8664 ns         8663 ns        80584 items_per_second=115.43M/s
   IntegerParsing<Int64Type>                      12173 ns        12172 ns        57294 items_per_second=82.158M/s
   IntegerParsing<UInt8Type>                       3369 ns         3369 ns       207573 items_per_second=296.845M/s
   IntegerParsing<UInt16Type>                      2102 ns         2102 ns       332411 items_per_second=475.832M/s
   IntegerParsing<UInt32Type>                      4962 ns         4961 ns       140831 items_per_second=201.572M/s
   IntegerParsing<UInt64Type>                      7191 ns         7190 ns       100415 items_per_second=139.078M/s
   
   IntegerFormatting<Int8Type>                     3812 ns         3812 ns       179090 items_per_second=262.339M/s
   IntegerFormatting<Int16Type>                    5027 ns         5027 ns       134540 items_per_second=198.932M/s
   IntegerFormatting<Int32Type>                    7389 ns         7388 ns        93547 items_per_second=135.355M/s
   IntegerFormatting<Int64Type>                   15756 ns        15754 ns        44352 items_per_second=63.4756M/s
   IntegerFormatting<UInt8Type>                    4056 ns         4056 ns       173893 items_per_second=246.56M/s
   IntegerFormatting<UInt16Type>                   5275 ns         5275 ns       132502 items_per_second=189.586M/s
   IntegerFormatting<UInt32Type>                   7541 ns         7540 ns        92745 items_per_second=132.63M/s
   IntegerFormatting<UInt64Type>                  17504 ns        17502 ns        40788 items_per_second=57.1355M/s
   ```
   * after:
   ```
   IntegerParsing<Int8Type>                        4084 ns         4083 ns       169535 items_per_second=244.921M/s
   IntegerParsing<Int16Type>                       4707 ns         4707 ns       148239 items_per_second=212.468M/s
   IntegerParsing<Int32Type>                       8991 ns         8990 ns        77470 items_per_second=111.238M/s
   IntegerParsing<Int64Type>                      12632 ns        12630 ns        55277 items_per_second=79.1756M/s
   IntegerParsing<UInt8Type>                       3475 ns         3475 ns       201119 items_per_second=287.803M/s
   IntegerParsing<UInt16Type>                      3784 ns         3784 ns       184693 items_per_second=264.29M/s
   IntegerParsing<UInt32Type>                      5609 ns         5608 ns       124533 items_per_second=178.323M/s
   IntegerParsing<UInt64Type>                      7552 ns         7550 ns        92385 items_per_second=132.442M/s
   
   IntegerFormatting<Int8Type>                     5973 ns         5972 ns       115765 items_per_second=167.445M/s
   IntegerFormatting<Int16Type>                    7325 ns         7324 ns        95107 items_per_second=136.541M/s
   IntegerFormatting<Int32Type>                   15128 ns        15126 ns        46259 items_per_second=66.1119M/s
   IntegerFormatting<Int64Type>                   18152 ns        18149 ns        43116 items_per_second=55.0988M/s
   IntegerFormatting<UInt8Type>                    6079 ns         6078 ns       114820 items_per_second=164.531M/s
   IntegerFormatting<UInt16Type>                   8158 ns         8157 ns        85571 items_per_second=122.597M/s
   IntegerFormatting<UInt32Type>                  10500 ns        10498 ns        66770 items_per_second=95.2558M/s
   IntegerFormatting<UInt64Type>                  20176 ns        20173 ns        34577 items_per_second=49.5716M/s
   ```
   
   However, CSV conversion benchmarks seem either affected or (slightly) improved:
   * before:
   ```
   Int64Conversion                  84572 ns        84558 ns         8320 items_per_second=98.5477M/s
   FloatConversion                 186815 ns       186786 ns         3770 items_per_second=42.8298M/s
   Decimal128Conversion            403464 ns       403407 ns         1715 items_per_second=16.5267M/s
   StringConversion                 58231 ns        58222 ns        12144 items_per_second=114.509M/s
   TimestampConversionDefault      156438 ns       156414 ns         4461 items_per_second=63.9328M/s
   TimestampConversionStrptime     472131 ns       472065 ns         1480 items_per_second=21.1835M/s
   ```
   * after:
   ```
   Int64Conversion                  70332 ns        70322 ns         9953 items_per_second=118.497M/s
   FloatConversion                 179511 ns       179482 ns         3823 items_per_second=44.5726M/s
   Decimal128Conversion            417192 ns       417133 ns         1678 items_per_second=15.9829M/s
   StringConversion                 58438 ns        58426 ns        12043 items_per_second=114.109M/s
   TimestampConversionDefault      154926 ns       154902 ns         4495 items_per_second=64.5568M/s
   TimestampConversionStrptime     514370 ns       514289 ns         1345 items_per_second=19.4443M/s
   ```
   
   So there doesn't seem to be any reason for concern, a priori.
   


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