matrix.rb

def generate_matrix(size)
  Array.new(size) { Array.new(size) { rand 10 } }
end

# Only for 3x3 matrices for the time being
# Refactor!
def determinant(matrix)
  (matrix[0][0] * ((matrix[1][1] * matrix[2][2]) - (matrix[2][1] * matrix[1][2]))) - (matrix[0][1] * ((matrix[1][0] * matrix[2][2]) - (matrix[2][0] * matrix[1][2]))) + (matrix[0][2] * ((matrix[1][0] * matrix[2][1]) - (matrix[2][0] * matrix[1][1])))
end

def put_matrix(matrix)
  matrix.each do |line|
    print '| '
    line.each { |element| print "#{element} " }
    puts '|'
  end
end

def benchmark
  100000.times do
    matrix = generate_matrix 3
    determinant matrix
  end
end

def prog
  put_matrix(matrix = generate_matrix(3))
  puts "Determinant = #{determinant matrix}"
end

benchmark

__END__
$ time ruby matrix.rb 
real	0m1.014s
user	0m0.856s
sys	0m0.004s

$ time jruby matrix.rb 
real	0m2.317s
user	0m1.972s
sys	0m0.128s