For the cases I have benchmarked concatenation with << has been faster than join on an array.
Here's a simple benchmark:
require "benchmark"
n = 100_000
Benchmark.bm(4) do |x|
x.report("<<") do
n.times do
"aaaaa " << "bbbbbb " << "ccccc " << "ddddd " << "eeeee " << "fffff"
end
end
x.report("join") do
n.times do
["aaaaa", "bbbbbb", "ccccc", "ddddd", "eeeee", "fffff"].join(" ")
end
end
end
user system total real
<< 0.140000 0.000000 0.140000 ( 0.143750)
join 0.230000 0.000000 0.230000 ( 0.228035)
Re:Ruby Tips, Part 5
by xentronium on Tuesday April 22, 2014 @07:46PM
(#7631214)
require "benchmark"
n = 100_000
A = "foo " * 20
B = "bar " * 20
C = "baz " * 20
D = "foobar " * 20
STRINGS = [A, B, C, D]
Benchmark.bm(4) do |x|
x.report("<<") do
n.times do
"" << A << B << C << D
end
end
x.report("join") do
n.times do
STRINGS.join
end
end
end
user system total real
<< 0.090000 0.010000 0.100000 ( 0.102411)
join 0.070000 0.010000 0.080000 ( 0.071142)
The way I have been building strings is to store the m strings in an Array and then join() it at the end (which should be only O(n)). The m small objects need to be allocated in both cases, the only difference being that we hold on to those and join them later on.
Am I missing something? I have never measured the performance on either of the these operations so I could be off the mark here.