added binary trees benchmark

tests/gc/bintrees.nim

@@ -0,0 +1,54 @@
+# -*- nimrod -*-
+
+import os, strutils
+
+type
+  PNode = ref TNode
+  TNode {.final, acyclic.} = object
+    left, right: PNode
+    item: int
+
+proc checkTree(node: PNode): int =
+  result = node.item
+  if node.left != nil:
+    inc result, checkTree(node.left) - checkTree(node.right)
+
+proc makeTreeAux(item, depth: int): PNode =
+  new(result)
+  result.item = item
+  if depth > 0:
+    result.left = makeTreeAux(2 * item - 1, depth - 1)
+    result.right = makeTreeAux(2 * item,    depth - 1)
+
+proc makeTree(item, depth: int): PNode =
+  #GC_disable()
+  result = makeTreeAux(item, depth)
+  #GC_enable()
+
+proc main =
+  var n = parseInt(paramStr(1))
+  const minDepth = 4
+  var maxDepth = if minDepth+2 > n: minDepth+2 else: n
+
+  var stretchDepth = maxDepth + 1
+
+  echo("stretch tree of depth ", stretchDepth, "\t check: ", checkTree(
+      makeTree(0, stretchDepth)))
+
+  var longLivedTree = makeTree(0, maxDepth)
+
+  var iterations = 1 shl maxDepth
+  for depth in countup (minDepth, stretchDepth-1, 2):
+    var check = 0
+    for i in 1..iterations:
+      check += checkTree(makeTree(i, depth)) + checkTree(makeTree(-i, depth))
+
+    echo(iterations*2, "\t trees of depth ", depth, "\t check: ", check)
+    iterations = iterations div 4
+
+  echo("long lived tree of depth ", maxDepth, "\t check: ",
+      longLivedTree.checkTree)
+  echo GC_getstatistics()
+
+main()
+