出于某种原因,我的 LinkedList
似乎优于我的 List
。我有一个 LinkedList
因为有一部分代码我必须重新排列 child 。重新排列之后的一切都只是简单地遍历数据并执行计算。我之前只是使用 Iterator
遍历 LinkedList
,但后来我认为我应该同时存储相同元素的 List
,所以我可以更快地迭代它们。不知何故,添加 List
并对其进行迭代对于完全相同的事情来说要慢得多。不确定这是怎么回事,所以任何信息都有帮助。
这里大致是我期望更快的代码:
class Program {
public static void Main(string[] args) {
var originalList = new List<Thing>();
for (var i = 0; i < 1000; i++) {
var t = new Thing();
t.x = 0d;
t.y = 0d;
originalList.Add(t);
}
var something = new Something(originalList);
for (var i = 0; i < 1000; i++) {
var start = DateTime.Now.Ticks / TimeSpan.TicksPerMillisecond;
something.iterate();
time += (DateTime.Now.Ticks / TimeSpan.TicksPerMillisecond) - start;
Console.Out.WriteLine(time / (i + 1));
}
}
class Thing {
public double x {get; set;}
public double y {get; set;}
}
class Something {
private List<Thing> things;
private LinkedList<Thing> things1 = new LinkedList<Thing>();
private List<Thing> things2 = new List<Thing>();
public Class(List<Thing> things) {
this.things = things;
for (var i = 0; i < things.Count; i++) {
things1.AddLast(things[i]);
things2.Add(things[i]);
}
}
public void iterate() {
//loops like this happen a few times, but the list is never changed, only the
//objects properties in the list
for (var i = 0; i < things2.Count; i++) {
var thing = things2[i];
thing.x += someDouble;
thing.y += someOtherDouble;
}
}
}
}
这是我首先做的,我认为应该慢一些:
class Program {
public static void Main(string[] args) {
var originalList = new List<Thing>();
for (var i = 0; i < 1000; i++) {
var t = new Thing();
t.x = 0d;
t.y = 0d;
originalList.Add(t);
}
var something = new Something(originalList);
for (var i = 0; i < 1000; i++) {
var start = DateTime.Now.Ticks / TimeSpan.TicksPerMillisecond;
something.iterate();
time += (DateTime.Now.Ticks / TimeSpan.TicksPerMillisecond) - start;
Console.Out.WriteLine(time / (i + 1));
}
}
class Thing {
public double x {get; set;}
public double y {get; set;}
}
class Something {
private List<Thing> things;
private LinkedList<Thing> things1 = new LinkedList<Thing>();
public Class(List<Thing> things) {
this.things = things;
for (var i = 0; i < things.Count; i++) {
things1.AddLast(things[i]);
}
}
public void iterate() {
//loops like this happen a few times, but the list is never changed, only the
//objects properties in the list
var iterator = things1.First;
while (iterator != null) {
var value = iterator.Value;
value.x += someDouble;
value.y += someOtherDouble;
iterator = iterator.Next;
}
}
}
}
最佳答案
因为它不编译,所以很难验证任何东西,所以我不能在我的机器上运行它,但仍然存在一些大问题:
- 您不应该使用
DateTime.Now
来衡量性能。而是使用能够进行高保真时间测量的Stopwatch
,例如:
var stopwatch = Stopwatch.StartNew(); //do stuff here stopwatch.Stop(); double timeInSeconds = stopwatch.Elapsed.TotalSeconds;
- 您的算法在以下行中存在根本性缺陷:
DateTime.Now.Ticks / TimeSpan.TicksPerMillisecond
刻度表示为整数(此处为long
),除法结果不是实数,而是被截断了。例如。 55/7 = 7
。因此,它绝对不是一种稳定的基准测试方式。
此外,使用更多元素运行基准测试并确保在 Release模式下进行。
关于c# - LinkedList 比 List 迭代更快?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/21316281/