median.m benchmarking branch vs branchless

function bench_mid_two_vals ()

  N = 1e7;
  m1 = int64 (randi (100, 1, N));
  m2 = int64 (randi (100, 1, N));
  samesign = sign (m1) == sign (m2);

  f_branchless = @() ...
    (samesign .* (m1 + (m2 - m1) / 2) + !samesign .* ((m1 + m2) / 2));

  f_masked = @() masked_impl (m1, m2, samesign);

  % warmup
  for i = 1:5
    f_branchless ();
    f_masked ();
  end

  runs = 20;
  t1 = zeros (1, runs);
  t2 = zeros (1, runs);

  for i = 1:runs
    tic; f_branchless (); t1(i) = toc;
    tic; f_masked ();    t2(i) = toc;
  end

  printf ("Branchless: %.3f ms\n", mean (t1)*1000);
  printf ("Masked:     %.3f ms\n", mean (t2)*1000);
  printf ("Speedup (masked / branchless): %.2fx\n", mean (t2)/mean (t1));

endfunction


function m = masked_impl (m1, m2, samesign)
  m = zeros (size (m1), "like", m1);
  m(samesign) = m1(samesign) + (m2(samesign) - m1(samesign)) / 2;
  m(!samesign) = (m1(!samesign) + m2(!samesign)) / 2;
endfunction