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// Copyright 2011 The Go Authors.  All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// This benchmark, taken from the shootout, tests garbage collector
// performance by generating and discarding large binary trees.

package go1

import "testing"

type binaryNode struct {
        item        int
        left, right *binaryNode
}

func bottomUpTree(item, depth int) *binaryNode {
        if depth <= 0 {
                return &binaryNode{item: item}
        }
        return &binaryNode{item, bottomUpTree(2*item-1, depth-1), bottomUpTree(2*item, depth-1)}
}

func (n *binaryNode) itemCheck() int {
        if n.left == nil {
                return n.item
        }
        return n.item + n.left.itemCheck() - n.right.itemCheck()
}

const minDepth = 4

func binarytree(n int) {
        maxDepth := n
        if minDepth+2 > n {
                maxDepth = minDepth + 2
        }
        stretchDepth := maxDepth + 1

        check := bottomUpTree(0, stretchDepth).itemCheck()
        //fmt.Printf("stretch tree of depth %d\t check: %d\n", stretchDepth, check)

        longLivedTree := bottomUpTree(0, maxDepth)

        for depth := minDepth; depth <= maxDepth; depth += 2 {
                iterations := 1 << uint(maxDepth-depth+minDepth)
                check = 0

                for i := 1; i <= iterations; i++ {
                        check += bottomUpTree(i, depth).itemCheck()
                        check += bottomUpTree(-i, depth).itemCheck()
                }
                //fmt.Printf("%d\t trees of depth %d\t check: %d\n", iterations*2, depth, check)
        }
        longLivedTree.itemCheck()
        //fmt.Printf("long lived tree of depth %d\t check: %d\n", maxDepth, longLivedTree.itemCheck())
}

func BenchmarkBinaryTree17(b *testing.B) {
        for i := 0; i < b.N; i++ {
                binarytree(17)
        }
}