diff --git a/benchmarks.yml b/benchmarks.yml
index 084524a..1fe4ea8 100644
--- a/benchmarks.yml
+++ b/benchmarks.yml
@@ -72,6 +72,12 @@ rubykon:
   desc: Ruby solver for Go (the boardgame.) Runs 1,000 iterations forward from an initial starting board.
 tinygql:
   desc: TinyGQL gem parsing a large file in pure Ruby
+nqueens:
+  desc: solver for the N-Queens problem
+sudoku:
+  desc: sudoku solver
+matmul:
+  desc: matrix multiplication benchmark
 
 #
 # MicroBenchmarks
diff --git a/benchmarks/matmul.rb b/benchmarks/matmul.rb
new file mode 100644
index 0000000..1345807
--- /dev/null
+++ b/benchmarks/matmul.rb
@@ -0,0 +1,43 @@
+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
+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
+end
+
+n = 300
+if ARGV.length >= 1
+	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]
+end
diff --git a/benchmarks/nqueens.rb b/benchmarks/nqueens.rb
new file mode 100644
index 0000000..28839be
--- /dev/null
+++ b/benchmarks/nqueens.rb
@@ -0,0 +1,44 @@
+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
+end
+
+n = 12
+if ARGV.length() > 0 then
+	n = ARGV[0].to_i
+end
+
+run_benchmark(40) do
+	nq_solve(n)
+end
diff --git a/benchmarks/sudoku.rb b/benchmarks/sudoku.rb
new file mode 100644
index 0000000..dbf7957
--- /dev/null
+++ b/benchmarks/sudoku.rb
@@ -0,0 +1,135 @@
+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
+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
+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
+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....."
+]
+mr, mc = sd_genmat()
+
+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
+end