diff --git a/benchmarks/matmul.rb b/benchmarks/matmul.rb
index 13458076..ce119a77 100644
--- a/benchmarks/matmul.rb
+++ b/benchmarks/matmul.rb
@@ -1,43 +1,46 @@
 require_relative '../harness/loader'
 
 def matgen(n)
-	tmp = 1.0 / n / n
-  	a = Array.new(n) { Array.new(n) { 0 } }
-	for i in 0 .. n-1
-		for j in 0 .. n-1
-			a[i][j] = tmp * (i - j) * (i + j)
-		end
-	end
-	return a
+  tmp = 1.0 / n / n
+  Array.new(n) { |i|
+    Array.new(n) { |j|
+      tmp * (i - j) * (i + j)
+    }
+  }
 end
 
 def matmul(a, b)
-	m = a.length
-	n = a[0].length
-	p = b[0].length
-  	c = Array.new(m) { Array.new(p) { 0 } }
-	for i in 0 .. m-1
-		ci = c[i]
-		for k in 0 .. n-1
-			aik = a[i][k]
-			bk = b[k]
-			for j in 0 .. p-1
-				ci[j] += aik * bk[j]
-			end
-		end
-	end
-	return c
+  m = a.length
+  n = a[0].length
+  p = b[0].length
+  c = Array.new(m) { Array.new(p, 0.0) }
+  for i in 0...m
+    ci = c[i]
+    ai = a[i]
+    k = 0
+    while k < n
+      aik = ai[k]
+      bk = b[k]
+      j = 0
+      while j < p
+        ci[j] += aik * bk[j]
+        j += 1
+      end
+      k += 1
+    end
+  end
+  c
 end
 
 n = 300
-if ARGV.length >= 1
-	n = ARGV[0].to_i
+if ARGV.length > 0
+  n = ARGV[0].to_i
 end
 n = n / 2 * 2
 
 run_benchmark(20) do
-	a = matgen(n)
-	b = matgen(n)
-	c = matmul(a, b)
-	#puts c[n/2][n/2]
+  a = matgen(n)
+  b = matgen(n)
+  c = matmul(a, b)
+  # puts c[n / 2][n / 2]
 end
diff --git a/benchmarks/nqueens.rb b/benchmarks/nqueens.rb
index 28839bee..42505f64 100644
--- a/benchmarks/nqueens.rb
+++ b/benchmarks/nqueens.rb
@@ -1,44 +1,46 @@
 require_relative '../harness/loader'
 
 def nq_solve(n)
-	a = Array.new(n) { -1 }
-	l = Array.new(n) { 0 }
-	c = Array.new(n) { 0 }
-	r = Array.new(n) { 0 }
-	y0 = (1<<n) - 1
-	m = 0
-	k = 0
-	while k >= 0 do
-		y = (l[k] | c[k] | r[k]) & y0
-		if (y ^ y0) >> (a[k] + 1) != 0 then
-			i = a[k] + 1
-			while i < n and (y & 1<<i) != 0 do
-				i += 1
-			end
-			if k < n - 1 then
-				z = 1<<i
-				a[k] = i
-				k += 1
-				l[k] = (l[k-1]|z)<<1
-				c[k] = c[k-1]|z
-				r[k] = (r[k-1]|z)>>1
-			else
-				m += 1
-				k -= 1
-			end
-		else
-			a[k] = -1
-			k -= 1
-		end
-	end
-	return m
+  a = Array.new(n, -1)
+  l = Array.new(n, 0)
+  c = Array.new(n, 0)
+  r = Array.new(n, 0)
+  y0 = (1 << n) - 1
+  m = 0
+  k = 0
+
+  while k >= 0
+    y = (l[k] | c[k] | r[k]) & y0
+    if (y ^ y0) >> (a[k] + 1) != 0
+      i = a[k] + 1
+      while i < n && (y & 1 << i) != 0
+        i += 1
+      end
+      if k < n - 1
+        z = 1 << i
+        a[k] = i
+        k += 1
+        l[k] = (l[k-1] | z) << 1
+        c[k] = c[k-1] | z
+        r[k] = (r[k-1] | z) >> 1
+      else
+        m += 1
+        k -= 1
+      end
+    else
+      a[k] = -1
+      k -= 1
+    end
+  end
+
+  m
 end
 
 n = 12
-if ARGV.length() > 0 then
-	n = ARGV[0].to_i
+if ARGV.length > 0
+  n = ARGV[0].to_i
 end
 
 run_benchmark(40) do
-	nq_solve(n)
+  nq_solve(n)
 end
diff --git a/benchmarks/sudoku.rb b/benchmarks/sudoku.rb
index dbf79576..2b90eb33 100644
--- a/benchmarks/sudoku.rb
+++ b/benchmarks/sudoku.rb
@@ -1,135 +1,230 @@
 require_relative '../harness/loader'
 
-def sd_genmat()
-	mr = Array.new(324) { [] }
-	mc = Array.new(729) { [] }
-	r = 0
-	(0...9).each do |i|
-		(0...9).each do |j|
-			(0...9).each do |k|
-				mc[r] = [ 9 * i + j, (i/3*3 + j/3) * 9 + k + 81, 9 * i + k + 162, 9 * j + k + 243 ]
-				r += 1
-			end
-		end
-	end
-	(0...729).each do |r|
-		(0...4).each do |c2|
-			mr[mc[r][c2]].push(r)
-		end
-	end
-	return mr, mc
+def sd_genmat
+  mr = Array.new(324) { [] }
+  mc = Array.new(729) { Array.new(4, 0) }
+  r = 0
+
+  i = 0
+  while i < 9
+    j = 0
+    while j < 9
+      k = 0
+      while k < 9
+        mcr = mc[r]
+        mcr[0] = 9 * i + j
+        mcr[1] = (i / 3 * 3 + j / 3) * 9 + k + 81
+        mcr[2] = 9 * i + k + 162
+        mcr[3] = 9 * j + k + 243
+        r += 1
+        k += 1
+      end
+      j += 1
+    end
+    i += 1
+  end
+
+  r2 = 0
+  while r2 < 729
+    c2 = 0
+    while c2 < 4
+      mr[mc[r2][c2]] << r2
+      c2 += 1
+    end
+    r2 += 1
+  end
+
+  [mr, mc]
+end
+
+def sd_update_forward(mr, mc, sr, sc, r)
+  min = 10
+  min_c = 0
+  mcr = mc[r]
+
+  c2 = 0
+  while c2 < 4
+    sc[mcr[c2]] += 128
+    c2 += 1
+  end
+
+  c2 = 0
+  while c2 < 4
+    mrc = mr[mcr[c2]]
+    r2 = 0
+    while r2 < 9
+      rr = mrc[r2]
+      if (sr[rr] += 1) == 1
+        p = mc[rr]
+        cc2 = 0
+        while cc2 < 4
+          cc = p[cc2]
+          if (sc[cc] -= 1) < min
+            min = sc[cc]
+            min_c = cc
+          end
+          cc2 += 1
+        end
+      end
+      r2 += 1
+    end
+    c2 += 1
+  end
+
+  [min, min_c]
 end
 
-def sd_update(mr, mc, sr, sc, r, v)
-	min, min_c = 10, 0
-	(0...4).each do |c2|
-		if v > 0 then sc[mc[r][c2]] += 128
-		else sc[mc[r][c2]] -= 128 end
-	end
-	(0...4).each do |c2|
-		c = mc[r][c2]
-		if v > 0 then
-			(0...9).each do |r2|
-				rr = mr[c][r2]
-				sr[rr] += + 1
-				if sr[rr] == 1 then
-					p = mc[rr]
-					sc[p[0]] -= 1; sc[p[1]] -= 1; sc[p[2]] -= 1; sc[p[3]] -= 1
-					if sc[p[0]] < min then min, min_c = sc[p[0]], p[0] end
-					if sc[p[1]] < min then min, min_c = sc[p[1]], p[1] end
-					if sc[p[2]] < min then min, min_c = sc[p[2]], p[2] end
-					if sc[p[3]] < min then min, min_c = sc[p[3]], p[3] end
-				end
-			end
-		else
-			(0...9).each do |r2|
-				rr = mr[c][r2]
-				sr[rr] -= 1
-				if sr[rr] == 0 then
-					p = mc[rr]
-					sc[p[0]] += 1; sc[p[1]] += 1; sc[p[2]] += 1; sc[p[3]] += 1
-				end
-			end
-		end
-	end
-	return min, min_c
+def sd_update_reverse(mr, mc, sr, sc, r)
+  c2 = 0
+  while c2 < 4
+    sc[mc[r][c2]] -= 128
+    c2 += 1
+  end
+
+  c2 = 0
+  while c2 < 4
+    c = mc[r][c2]
+    r2 = 0
+    while r2 < 9
+      rr = mr[c][r2]
+      if (sr[rr] -= 1) == 0
+        p = mc[rr]
+
+        sc[p[0]] += 1
+        sc[p[1]] += 1
+        sc[p[2]] += 1
+        sc[p[3]] += 1
+      end
+      r2 += 1
+    end
+    c2 += 1
+  end
 end
 
 def sd_solve(mr, mc, s)
-	ret, sr, sc, hints = [], Array.new(729) { 0 }, Array.new(324) { 9 }, 0
-	(0...81).each do |i|
-		a = (s[i].chr >= '1' and s[i].chr <= '9')? s[i].ord - 49 : -1
-		if a >= 0 then sd_update(mr, mc, sr, sc, i * 9 + a, 1); hints += 1 end
-	end
-	cr, cc = Array.new(81) { -1 }, Array.new(81) { 0 }
-	i, min, dir = 0, 10, 1
-	loop do
-		while i >= 0 and i < 81 - hints do
-			if dir == 1 then
-				if min > 1 then
-					(0...324).each do |c|
-						if sc[c] < min then
-							min, cc[i] = sc[c], c
-							if min < 2 then break end
-						end
-					end
-				end
-				if min == 0 or min == 10 then cr[i], dir, i = -1, -1, i - 1 end
-			end
-			c = cc[i]
-			if dir == -1 and cr[i] >= 0 then sd_update(mr, mc, sr, sc, mr[c][cr[i]], -1) end
-			r2_ = 9
-			(cr[i]+1...9).each do |r2|
-				if sr[mr[c][r2]] == 0 then r2_ = r2; break end
-			end
-			if r2_ < 9 then
-				min, cc[i+1] = sd_update(mr, mc, sr, sc, mr[c][r2_], 1)
-				cr[i], dir, i = r2_, 1, i + 1
-			else cr[i], dir, i = -1, -1, i - 1 end
-		end
-		if i < 0 then break end
-		o = []
-		(0...81).each do |j| o.push(s[j].ord - 48) end
-		(0...i).each do |j|
-			r = mr[cc[j]][cr[j]]
-			o[r/9] = r % 9 + 1
-		end
-		ret.push(o)
-		i, dir = i - 1, -1
-	end
-	return ret
+  sr = Array.new(729, 0)
+  sc = Array.new(324, 9)
+  hints = 0
+
+  i = 0
+  while i < 81
+    char = s[i]
+    a = (char >= '1' && char <= '9') ? char.ord - 49 : -1
+    if a >= 0
+      sd_update_forward(mr, mc, sr, sc, i * 9 + a)
+      hints += 1
+    end
+    i += 1
+  end
+
+  cr = Array.new(81, -1)
+  cc = Array.new(81, 0)
+  i = 0
+  min = 10
+  dir = 1
+
+  while true
+    while i >= 0 && i < 81 - hints
+      if dir == 1
+        if min > 1
+          c = 0
+          while c < 324
+            if sc[c] < min
+              min = sc[c]
+              cc[i] = c
+              break if min < 2
+            end
+            c += 1
+          end
+        end
+
+        if min == 0 || min == 10
+          cr[i] = dir = -1
+          i -= 1
+        end
+      end
+
+      c = cc[i]
+      if dir == -1 && cr[i] >= 0
+        sd_update_reverse(mr, mc, sr, sc, mr[c][cr[i]])
+      end
+
+      r2 = cr[i] + 1
+      while r2 < 9 && sr[mr[c][r2]] != 0
+        r2 += 1
+      end
+
+      if r2 < 9
+        min, cc[i + 1] = sd_update_forward(mr, mc, sr, sc, mr[c][r2])
+        cr[i] = r2
+        dir = 1
+        i += 1
+      else
+        cr[i] = -1
+        dir = -1
+        i -= 1
+      end
+    end
+
+    break if i < 0
+
+    o = Array.new(81, 0)
+    j = 0
+    while j < 81
+      o[j] = s[j].ord - 48
+      j += 1
+    end
+
+    j = 0
+    while j < i
+      r = mr[cc[j]][cr[j]]
+      o[r / 9] = r % 9 + 1
+      j += 1
+    end
+    o.join # puts o.join
+
+    i -= 1
+    dir = -1
+  end
 end
 
 hard20 = [
-	"..............3.85..1.2.......5.7.....4...1...9.......5......73..2.1........4...9",
-	".......12........3..23..4....18....5.6..7.8.......9.....85.....9...4.5..47...6...",
-	".2..5.7..4..1....68....3...2....8..3.4..2.5.....6...1...2.9.....9......57.4...9..",
-	"........3..1..56...9..4..7......9.5.7.......8.5.4.2....8..2..9...35..1..6........",
-	"12.3....435....1....4........54..2..6...7.........8.9...31..5.......9.7.....6...8",
-	"1.......2.9.4...5...6...7...5.9.3.......7.......85..4.7.....6...3...9.8...2.....1",
-	".......39.....1..5..3.5.8....8.9...6.7...2...1..4.......9.8..5..2....6..4..7.....",
-	"12.3.....4.....3....3.5......42..5......8...9.6...5.7...15..2......9..6......7..8",
-	"..3..6.8....1..2......7...4..9..8.6..3..4...1.7.2.....3....5.....5...6..98.....5.",
-	"1.......9..67...2..8....4......75.3...5..2....6.3......9....8..6...4...1..25...6.",
-	"..9...4...7.3...2.8...6...71..8....6....1..7.....56...3....5..1.4.....9...2...7..",
-	"....9..5..1.....3...23..7....45...7.8.....2.......64...9..1.....8..6......54....7",
-	"4...3.......6..8..........1....5..9..8....6...7.2........1.27..5.3....4.9........",
-	"7.8...3.....2.1...5.........4.....263...8.......1...9..9.6....4....7.5...........",
-	"3.7.4...........918........4.....7.....16.......25..........38..9....5...2.6.....",
-	"........8..3...4...9..2..6.....79.......612...6.5.2.7...8...5...1.....2.4.5.....3",
-	".......1.4.........2...........5.4.7..8...3....1.9....3..4..2...5.1........8.6...",
-	".......12....35......6...7.7.....3.....4..8..1...........12.....8.....4..5....6..",
-	"1.......2.9.4...5...6...7...5.3.4.......6........58.4...2...6...3...9.8.7.......1",
-	".....1.2.3...4.5.....6....7..2.....1.8..9..3.4.....8..5....2....9..3.4....67....."
+  "..............3.85..1.2.......5.7.....4...1...9.......5......73..2.1........4...9",
+  ".......12........3..23..4....18....5.6..7.8.......9.....85.....9...4.5..47...6...",
+  ".2..5.7..4..1....68....3...2....8..3.4..2.5.....6...1...2.9.....9......57.4...9..",
+  "........3..1..56...9..4..7......9.5.7.......8.5.4.2....8..2..9...35..1..6........",
+  "12.3....435....1....4........54..2..6...7.........8.9...31..5.......9.7.....6...8",
+  "1.......2.9.4...5...6...7...5.9.3.......7.......85..4.7.....6...3...9.8...2.....1",
+  ".......39.....1..5..3.5.8....8.9...6.7...2...1..4.......9.8..5..2....6..4..7.....",
+  "12.3.....4.....3....3.5......42..5......8...9.6...5.7...15..2......9..6......7..8",
+  "..3..6.8....1..2......7...4..9..8.6..3..4...1.7.2.....3....5.....5...6..98.....5.",
+  "1.......9..67...2..8....4......75.3...5..2....6.3......9....8..6...4...1..25...6.",
+  "..9...4...7.3...2.8...6...71..8....6....1..7.....56...3....5..1.4.....9...2...7..",
+  "....9..5..1.....3...23..7....45...7.8.....2.......64...9..1.....8..6......54....7",
+  "4...3.......6..8..........1....5..9..8....6...7.2........1.27..5.3....4.9........",
+  "7.8...3.....2.1...5.........4.....263...8.......1...9..9.6....4....7.5...........",
+  "3.7.4...........918........4.....7.....16.......25..........38..9....5...2.6.....",
+  "........8..3...4...9..2..6.....79.......612...6.5.2.7...8...5...1.....2.4.5.....3",
+  ".......1.4.........2...........5.4.7..8...3....1.9....3..4..2...5.1........8.6...",
+  ".......12....35......6...7.7.....3.....4..8..1...........12.....8.....4..5....6..",
+  "1.......2.9.4...5...6...7...5.3.4.......6........58.4...2...6...3...9.8.7.......1",
+  ".....1.2.3...4.5.....6....7..2.....1.8..9..3.4.....8..5....2....9..3.4....67....."
 ]
-mr, mc = sd_genmat()
+
+mr, mc = sd_genmat
+
+n = 4
+if ARGV.length > 0
+  n = ARGV[0].to_i
+end
 
 run_benchmark(20) do
-	n = 4
-	(0...n).each do |i|
-		hard20.each do |l|
-			ret = sd_solve(mr, mc, l)
-			ret.each do |s| s.join end
-		end
-	end
+  i = 0
+  while i < n
+    hard20.each do |line|
+      sd_solve(mr, mc, line)
+      # puts ""
+    end
+    i += 1
+  end
 end