binary-tree-freelist.go

Documentation: golang.org/x/exp/shootout

     1  //go:build ignore
     2  // +build ignore
     3  
     4  /*
     5  Redistribution and use in source and binary forms, with or without
     6  modification, are permitted provided that the following conditions are met:
     7  
     8      * Redistributions of source code must retain the above copyright
     9      notice, this list of conditions and the following disclaimer.
    10  
    11      * Redistributions in binary form must reproduce the above copyright
    12      notice, this list of conditions and the following disclaimer in the
    13      documentation and/or other materials provided with the distribution.
    14  
    15      * Neither the name of "The Computer Language Benchmarks Game" nor the
    16      name of "The Computer Language Shootout Benchmarks" nor the names of
    17      its contributors may be used to endorse or promote products derived
    18      from this software without specific prior written permission.
    19  
    20  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
    21  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
    22  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
    23  ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
    24  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
    25  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
    26  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
    27  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
    28  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
    29  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
    30  POSSIBILITY OF SUCH DAMAGE.
    31  */
    32  
    33  /* The Computer Language Benchmarks Game
    34   * http://shootout.alioth.debian.org/
    35   *
    36   * contributed by The Go Authors.
    37   * based on C program by Kevin Carson
    38   */
    39  
    40  package main
    41  
    42  import (
    43  	"flag"
    44  	"fmt"
    45  )
    46  
    47  var n = flag.Int("n", 15, "depth")
    48  
    49  type Node struct {
    50  	item        int
    51  	left, right *Node
    52  }
    53  
    54  type Arena struct {
    55  	head *Node
    56  }
    57  
    58  var arena Arena
    59  
    60  func (n *Node) free() {
    61  	if n.left != nil {
    62  		n.left.free()
    63  	}
    64  	if n.right != nil {
    65  		n.right.free()
    66  	}
    67  	n.left = arena.head
    68  	arena.head = n
    69  }
    70  
    71  func (a *Arena) New(item int, left, right *Node) *Node {
    72  	if a.head == nil {
    73  		nodes := make([]Node, 3<<uint(*n))
    74  		for i := 0; i < len(nodes)-1; i++ {
    75  			nodes[i].left = &nodes[i+1]
    76  		}
    77  		a.head = &nodes[0]
    78  	}
    79  	n := a.head
    80  	a.head = a.head.left
    81  	n.item = item
    82  	n.left = left
    83  	n.right = right
    84  	return n
    85  }
    86  
    87  func bottomUpTree(item, depth int) *Node {
    88  	if depth <= 0 {
    89  		return arena.New(item, nil, nil)
    90  	}
    91  	return arena.New(item, bottomUpTree(2*item-1, depth-1), bottomUpTree(2*item, depth-1))
    92  }
    93  
    94  func (n *Node) itemCheck() int {
    95  	if n.left == nil {
    96  		return n.item
    97  	}
    98  	return n.item + n.left.itemCheck() - n.right.itemCheck()
    99  }
   100  
   101  const minDepth = 4
   102  
   103  func main() {
   104  	flag.Parse()
   105  
   106  	maxDepth := *n
   107  	if minDepth+2 > *n {
   108  		maxDepth = minDepth + 2
   109  	}
   110  	stretchDepth := maxDepth + 1
   111  
   112  	check := bottomUpTree(0, stretchDepth).itemCheck()
   113  	fmt.Printf("stretch tree of depth %d\t check: %d\n", stretchDepth, check)
   114  
   115  	longLivedTree := bottomUpTree(0, maxDepth)
   116  
   117  	for depth := minDepth; depth <= maxDepth; depth += 2 {
   118  		iterations := 1 << uint(maxDepth-depth+minDepth)
   119  		check = 0
   120  
   121  		for i := 1; i <= iterations; i++ {
   122  			t := bottomUpTree(i, depth)
   123  			check += t.itemCheck()
   124  			t.free()
   125  			t = bottomUpTree(-i, depth)
   126  			check += t.itemCheck()
   127  			t.free()
   128  		}
   129  		fmt.Printf("%d\t trees of depth %d\t check: %d\n", iterations*2, depth, check)
   130  	}
   131  	fmt.Printf("long lived tree of depth %d\t check: %d\n", maxDepth, longLivedTree.itemCheck())
   132  }
   133
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