New string generator

[lemire]

We can hook up our mantissa to string generator. For dragonbox, this leads to a new variant (dragonboxlm). It produces slightly longer strings (because of the exponential) at almost exactly the same speed. We also make teju_jagua more competitive. The results are not super exciting in the sense that there is no performance breakthrough, but it is a bit interesting conceptually to plug in a new string generator.

$ ./build/benchmarks/benchmark -a box -a teju
number type: binary64 (double)
# parsing random numbers
available models (-m): uniform_01 logspace_all centered non_centered simple_uniform simple_int one_over_rand integer_uniform
model: generate random numbers uniformly in the interval [0.000000,1.000000]
volume: 100000 floats
# You can also provide a filename (with the -f flag): it should contain one string per line corresponding to a number
# skipping just_string
# filtered out dragon4
# filtered out netlib
# skipping errol3
# filtered out fmt_format
# filtered out grisu3
# filtered out grisu_exact
# filtered out schubfach
dragonboxlm                   :   769.32 MB/s (+/- 32.0 %)     2.12 MB     27.50 ns/f    36.36 Mfloat/s
                                    9.90 i/B   209.46 i/f (+/- 0.0 %)      4.14 c/B    87.60 c/f (+/- 0.2 %)
                                    2.39 i/c      0.00 b/f                 0.00 bm/f      3.19 GHz
dragonbox                     :   731.11 MB/s (+/- 0.8 %)     2.02 MB     27.57 ns/f    36.27 Mfloat/s
                                   11.88 i/B   239.53 i/f (+/- 0.0 %)      4.36 c/B    87.92 c/f (+/- 0.8 %)
                                    2.72 i/c      0.00 b/f                 0.00 bm/f      3.19 GHz
# filtered out ryu
teju_jagua                    :   711.14 MB/s (+/- 1.7 %)     2.12 MB     29.75 ns/f    33.61 Mfloat/s
                                    9.80 i/B   207.30 i/f (+/- 0.0 %)      4.48 c/B    94.83 c/f (+/- 1.7 %)
                                    2.19 i/c      0.00 b/f                 0.00 bm/f      3.19 GHz
# filtered out double_conversion
# filtered out swiftDtoa
# filtered out yy_double
# filtered out std::to_chars

$ ./build/benchmarks/benchmark -a box -a teju -f data/canada.txt
number type: binary64 (double)
# read 111126 lines
# skipping just_string
# filtered out dragon4
# filtered out netlib
# skipping errol3
# filtered out fmt_format
# filtered out grisu3
# filtered out grisu_exact
# filtered out schubfach
dragonboxlm                   :   628.66 MB/s (+/- 21.9 %)     2.20 MB     31.50 ns/f    31.75 Mfloat/s
                                   16.93 i/B   335.25 i/f (+/- 0.0 %)      5.07 c/B   100.36 c/f (+/- 1.0 %)
                                    3.34 i/c      0.00 b/f                 0.00 bm/f      3.19 GHz
dragonbox                     :   602.10 MB/s (+/- 1.2 %)     2.09 MB     31.22 ns/f    32.03 Mfloat/s
                                   19.28 i/B   362.47 i/f (+/- -0.0 %)      5.29 c/B    99.47 c/f (+/- 1.2 %)
                                    3.64 i/c      0.00 b/f                 0.00 bm/f      3.19 GHz
# filtered out ryu
teju_jagua                    :   523.48 MB/s (+/- 1.2 %)     2.20 MB     37.82 ns/f    26.44 Mfloat/s
                                   17.31 i/B   342.78 i/f (+/- -0.0 %)      6.09 c/B   120.50 c/f (+/- 1.2 %)
                                    2.84 i/c      0.00 b/f                 0.00 bm/f      3.19 GHz
# filtered out double_conversion
# filtered out swiftDtoa
# filtered out yy_double
# filtered out std::to_chars

[jaja360]

Looks good ! I think we can merge.

[lemire]

Merged.