String#squeeze is faster than String#gsub

b.rb

require "benchmark"

str1 = "a     b"
str2 = "a b"

N = 100000

Benchmark.bmbm do |x|
  x.report("gsub") do
    N.times do
      str1.gsub(/ +/, " ")
    end
  end
  x.report("gsub w/o spaces") do
    N.times do
      str2.gsub(/ +/, " ")
    end
  end
  x.report("squeeze") do
    N.times do
      str1.squeeze(" ")
    end
  end
  x.report("squeeze w/o spaces") do
    N.times do
      str2.squeeze(" ")
    end
  end
end

result.txt

$ ruby -v b.rb
ruby 2.5.3p105 (2018-10-18 revision 65156) [x86_64-linux]
Rehearsal ------------------------------------------------------
gsub                 0.144169   0.000000   0.144169 (  0.144228)
gsub w/o spaces      0.141979   0.000000   0.141979 (  0.142020)
squeeze              0.019956   0.000000   0.019956 (  0.019966)
squeeze w/o spaces   0.020379   0.000000   0.020379 (  0.020383)
--------------------------------------------- total: 0.326483sec

                         user     system      total        real
gsub                 0.147720   0.000000   0.147720 (  0.147767)
gsub w/o spaces      0.138309   0.000000   0.138309 (  0.138351)
squeeze              0.019598   0.000000   0.019598 (  0.019602)
squeeze w/o spaces   0.020238   0.000000   0.020238 (  0.020244)