Added benchmark tool and some benchmarks.

tests/benchmarks/fannkuch.nim

@@ -0,0 +1,69 @@
+import os
+import strutils
+
+proc fannkuch (n: int): int =
+    var 
+        count: seq[int]
+        maxFlips = 0
+        m        = n-1
+        r        = n
+        check    = 0
+        perm1: seq[int]
+        perm:  seq[int]
+
+    newSeq (count, n+1)
+    newSeq (perm1, n)
+    newSeq (perm, n)
+    for i in 0 .. n-1:
+        count[i] = i+1
+        perm1[i] = i
+        perm[i]  = i
+    count[n] = n+1
+
+    while True:
+        if check < 30:
+            for i in items (perm1):
+                write (stdout, $(i+1))
+            echo ("")
+            inc (check)
+
+        while r != 1:
+            count[r-1] = r
+            dec (r)
+
+        if perm1[0] != 0 and perm1[m] != m:
+            # perm = perm1
+            # The above line is between 3 and 4 times slower than the loop below!
+            for i in 0 .. n-1:
+                perm[i] = perm1[i]
+            var flipsCount = 0
+            var k = perm[0]
+            while k != 0:
+                for i in 0 .. (k div 2):
+                    swap (perm[i], perm[k-i])
+                inc (flipsCount)
+                k = perm[0]
+
+            if flipsCount > maxFlips:
+                maxFlips = flipsCount
+
+        block makePerm:
+            while r != n:
+                var tmp = perm1[0]
+                # # perm1.delete (0)
+                # # perm1.insert (tmp, r)
+                # # The above is about twice as slow as the following:
+                # moveMem (addr (perm1[0]), addr (perm1[1]), r * sizeof (int))
+                # The call to moveMem is about 50% slower than the loop below!
+                for i in 0 .. r-1:
+                    perm1[i] = perm1[i+1]
+                perm1[r] = tmp
+                
+                dec (count[r])
+                if count[r] > 0:
+                    break makePerm
+                inc (r)
+            return maxFlips
+
+var n = 10
+echo ("Pfannkuchen(" & $n & ") = " & $fannkuch (n))