Benchmark checking columnwise equality in two-dimensional arrays

columns_equal.rb

require "benchmark/ips"

ARRAY_SIZE = 5 # 5 rows and 5 columns
CHANCE = 0.33

# Returns the given 5-element array with a 33% chance of one item being changed
def dirty_row(row)
  return row if rand > CHANCE
  row.dup.tap { row[rand 0..(ARRAY_SIZE - 1)] = rand 0..99 }
end

# Returns a 5x5 array in which each value is equal to the other values in the
# same "column", but some values may be randomly changed
def rand_5x5
  col_vals = Array.new(ARRAY_SIZE) { rand 0..99 }
  Array.new(ARRAY_SIZE) { dirty_row(col_vals) }
end

# 3.times { puts rand_5x5.map {|row| row.map {|n| "%4i" % n }.join }; puts }

# Generate 100 random 5x5 arrays
testcases = Array.new(100) { rand_5x5 }

def meth_a(arr)
  first_row, *rest = arr

  rest.all? do |row|
    row.each_with_index.all? do |item, col_idx|
      row[col_idx] == first_row[col_idx]
    end
  end
end

def meth_b(arr)
  arr.transpose.all? {|row| row.uniq.size == 1 }
end

Benchmark.ips do |x|
  x.report("meth_a") { testcases.each {|testcase| meth_a(testcase) } }
  x.report("meth_b") { testcases.each {|testcase| meth_b(testcase) } }
  x.compare!
end

result.txt

Calculating -------------------------------------
              meth_a       410 i/100ms
              meth_b       302 i/100ms
-------------------------------------------------
              meth_a     4118.8 (±1.7%) i/s -      20910 in   5.078154s
              meth_b     3089.2 (±2.7%) i/s -      15704 in   5.087200s

Comparison:
              meth_a:     4118.8 i/s
              meth_b:     3089.2 i/s - 1.33x slower