C99 implementation of Peter Norvigs spelling corrector.
Input files can be downloaded here:
On my machine, using hyperfine I got:
$ hyperfine --warmup 3 "./spell_O1" "./spell_O2" "./spell_O3" "./spell_Ofast" "./spell_O2_fast-math"
Benchmark 1: ./spell_O1
Time (mean ± σ): 2.461 s ± 0.029 s [User: 2.442 s, System: 0.016 s]
Range (min … max): 2.426 s … 2.518 s 10 runs
Benchmark 2: ./spell_O2
Time (mean ± σ): 2.429 s ± 0.035 s [User: 2.408 s, System: 0.017 s]
Range (min … max): 2.385 s … 2.497 s 10 runs
Benchmark 3: ./spell_O3
Time (mean ± σ): 3.016 s ± 0.032 s [User: 2.992 s, System: 0.019 s]
Range (min … max): 2.949 s … 3.058 s 10 runs
Benchmark 4: ./spell_Ofast
Time (mean ± σ): 2.982 s ± 0.009 s [User: 2.956 s, System: 0.021 s]
Range (min … max): 2.967 s … 2.994 s 10 runs
Benchmark 5: ./spell_O2_fast-math
Time (mean ± σ): 2.938 s ± 0.006 s [User: 2.918 s, System: 0.017 s]
Range (min … max): 2.929 s … 2.947 s 10 runs
Summary
'./spell_O2' ran
1.01 ± 0.02 times faster than './spell_O1'
1.21 ± 0.02 times faster than './spell_O2_fast-math'
1.23 ± 0.02 times faster than './spell_Ofast'
1.24 ± 0.02 times faster than './spell_O3'
That is why I use -O2.