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      1 /*
      2 Redistribution and use in source and binary forms, with or without
      3 modification, are permitted provided that the following conditions are met:
      4 
      5     * Redistributions of source code must retain the above copyright
      6     notice, this list of conditions and the following disclaimer.
      7 
      8     * Redistributions in binary form must reproduce the above copyright
      9     notice, this list of conditions and the following disclaimer in the
     10     documentation and/or other materials provided with the distribution.
     11 
     12     * Neither the name of "The Computer Language Benchmarks Game" nor the
     13     name of "The Computer Language Shootout Benchmarks" nor the names of
     14     its contributors may be used to endorse or promote products derived
     15     from this software without specific prior written permission.
     16 
     17 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
     18 AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     19 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     20 ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
     21 LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     22 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     23 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     24 INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     25 CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     26 ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     27 POSSIBILITY OF SUCH DAMAGE.
     28 */
     29 
     30 /* The Computer Language Benchmarks Game
     31  * http://shootout.alioth.debian.org/
     32  *
     33  * contributed by The Go Authors.
     34  * based on C program by Kevin Carson
     35  */
     36 
     37 package main
     38 
     39 import (
     40 	"flag"
     41 	"fmt"
     42 )
     43 
     44 var n = flag.Int("n", 15, "depth")
     45 
     46 type Node struct {
     47 	item        int
     48 	left, right *Node
     49 }
     50 
     51 type Arena struct {
     52 	head *Node
     53 }
     54 
     55 var arena Arena
     56 
     57 func (n *Node) free() {
     58 	if n.left != nil {
     59 		n.left.free()
     60 	}
     61 	if n.right != nil {
     62 		n.right.free()
     63 	}
     64 	n.left = arena.head
     65 	arena.head = n
     66 }
     67 
     68 func (a *Arena) New(item int, left, right *Node) *Node {
     69 	if a.head == nil {
     70 		nodes := make([]Node, 3<<uint(*n))
     71 		for i := 0; i < len(nodes)-1; i++ {
     72 			nodes[i].left = &nodes[i+1]
     73 		}
     74 		a.head = &nodes[0]
     75 	}
     76 	n := a.head
     77 	a.head = a.head.left
     78 	n.item = item
     79 	n.left = left
     80 	n.right = right
     81 	return n
     82 }
     83 
     84 func bottomUpTree(item, depth int) *Node {
     85 	if depth <= 0 {
     86 		return arena.New(item, nil, nil)
     87 	}
     88 	return arena.New(item, bottomUpTree(2*item-1, depth-1), bottomUpTree(2*item, depth-1))
     89 }
     90 
     91 func (n *Node) itemCheck() int {
     92 	if n.left == nil {
     93 		return n.item
     94 	}
     95 	return n.item + n.left.itemCheck() - n.right.itemCheck()
     96 }
     97 
     98 const minDepth = 4
     99 
    100 func main() {
    101 	flag.Parse()
    102 
    103 	maxDepth := *n
    104 	if minDepth+2 > *n {
    105 		maxDepth = minDepth + 2
    106 	}
    107 	stretchDepth := maxDepth + 1
    108 
    109 	check := bottomUpTree(0, stretchDepth).itemCheck()
    110 	fmt.Printf("stretch tree of depth %d\t check: %d\n", stretchDepth, check)
    111 
    112 	longLivedTree := bottomUpTree(0, maxDepth)
    113 
    114 	for depth := minDepth; depth <= maxDepth; depth += 2 {
    115 		iterations := 1 << uint(maxDepth-depth+minDepth)
    116 		check = 0
    117 
    118 		for i := 1; i <= iterations; i++ {
    119 			t := bottomUpTree(i, depth)
    120 			check += t.itemCheck()
    121 			t.free()
    122 			t = bottomUpTree(-i, depth)
    123 			check += t.itemCheck()
    124 			t.free()
    125 		}
    126 		fmt.Printf("%d\t trees of depth %d\t check: %d\n", iterations*2, depth, check)
    127 	}
    128 	fmt.Printf("long lived tree of depth %d\t check: %d\n", maxDepth, longLivedTree.itemCheck())
    129 }
    130