Julia JIT编译、@时间和分配数

我刚刚开始评估Julia（版本0.6.0），并测试了如何调整大小！还有sizehint！可能会影响性能。我使用@time宏

文档中说“运行一次JIT编译”，但如果我们检查分配的数量，似乎运行一次是不够的

模块测试
函数测试（x:：Int64；hint:：Bool=false，resize:：Bool=false）
A:：数组{Int64}=[]
n：：Int64=x
如果调整大小
调整大小！（A，n）
因为我在1:n
A[i]=i
结束
其他的
如果提示sizehint！（A，n）结束
因为我在1:n
推（A，i）
结束
结束
A[完]
结束
结束
导入测试
#测试。测试（1）；#(1)
#测试。测试（1，提示=true）#(2)
#Test.Test（1，resize=true）#(3)
@时间测试。测试（10_000_000）
@时间测试。测试（10_000_000，提示=true）
@时间测试。测试（10_000，resize=true）

对于不同的“JIT预编译”调用，我得到了不同的结果：

上述代码的结果：

    0.494120 seconds (11.02 k allocations: 129.706 MiB, 22.77% gc time)
    0.141155 seconds (3.43 k allocations: 76.537 MiB, 41.94% gc time)
    0.068319 seconds (9 allocations: 76.294 MiB, 76.99% gc time)

如果（1）未注释：

    0.520939 seconds (112 allocations: 129.007 MiB, 21.79% gc time)
    0.140845 seconds (3.43 k allocations: 76.537 MiB, 42.35% gc time)
    0.068741 seconds (9 allocations: 76.294 MiB, 77.55% gc time)

    0.586479 seconds (112 allocations: 129.007 MiB, 19.28% gc time)
    0.117521 seconds (9 allocations: 76.294 MiB, 50.56% gc time)
    0.068275 seconds (9 allocations: 76.294 MiB, 76.84% gc time)

    0.509668 seconds (112 allocations: 129.007 MiB, 21.61% gc time)
    0.112276 seconds (9 allocations: 76.294 MiB, 50.58% gc time)
    0.065123 seconds (9 allocations: 76.294 MiB, 76.34% gc time)

    0.497802 seconds (240 allocations: 129.016 MiB, 22.53% gc time)
    0.117035 seconds (11 allocations: 76.294 MiB, 52.56% gc time)
    0.067170 seconds (11 allocations: 76.294 MiB, 76.93% gc time)

如果（1）和（2）未注释：

    0.520939 seconds (112 allocations: 129.007 MiB, 21.79% gc time)
    0.140845 seconds (3.43 k allocations: 76.537 MiB, 42.35% gc time)
    0.068741 seconds (9 allocations: 76.294 MiB, 77.55% gc time)

    0.586479 seconds (112 allocations: 129.007 MiB, 19.28% gc time)
    0.117521 seconds (9 allocations: 76.294 MiB, 50.56% gc time)
    0.068275 seconds (9 allocations: 76.294 MiB, 76.84% gc time)

    0.509668 seconds (112 allocations: 129.007 MiB, 21.61% gc time)
    0.112276 seconds (9 allocations: 76.294 MiB, 50.58% gc time)
    0.065123 seconds (9 allocations: 76.294 MiB, 76.34% gc time)

    0.497802 seconds (240 allocations: 129.016 MiB, 22.53% gc time)
    0.117035 seconds (11 allocations: 76.294 MiB, 52.56% gc time)
    0.067170 seconds (11 allocations: 76.294 MiB, 76.93% gc time)

如果（1）和（2）和（3）未注释：

    0.520939 seconds (112 allocations: 129.007 MiB, 21.79% gc time)
    0.140845 seconds (3.43 k allocations: 76.537 MiB, 42.35% gc time)
    0.068741 seconds (9 allocations: 76.294 MiB, 77.55% gc time)

    0.586479 seconds (112 allocations: 129.007 MiB, 19.28% gc time)
    0.117521 seconds (9 allocations: 76.294 MiB, 50.56% gc time)
    0.068275 seconds (9 allocations: 76.294 MiB, 76.84% gc time)

    0.509668 seconds (112 allocations: 129.007 MiB, 21.61% gc time)
    0.112276 seconds (9 allocations: 76.294 MiB, 50.58% gc time)
    0.065123 seconds (9 allocations: 76.294 MiB, 76.34% gc time)

    0.497802 seconds (240 allocations: 129.016 MiB, 22.53% gc time)
    0.117035 seconds (11 allocations: 76.294 MiB, 52.56% gc time)
    0.067170 seconds (11 allocations: 76.294 MiB, 76.93% gc time)

如果（3）未注释：

    0.520939 seconds (112 allocations: 129.007 MiB, 21.79% gc time)
    0.140845 seconds (3.43 k allocations: 76.537 MiB, 42.35% gc time)
    0.068741 seconds (9 allocations: 76.294 MiB, 77.55% gc time)

    0.586479 seconds (112 allocations: 129.007 MiB, 19.28% gc time)
    0.117521 seconds (9 allocations: 76.294 MiB, 50.56% gc time)
    0.068275 seconds (9 allocations: 76.294 MiB, 76.84% gc time)

    0.509668 seconds (112 allocations: 129.007 MiB, 21.61% gc time)
    0.112276 seconds (9 allocations: 76.294 MiB, 50.58% gc time)
    0.065123 seconds (9 allocations: 76.294 MiB, 76.34% gc time)

    0.497802 seconds (240 allocations: 129.016 MiB, 22.53% gc time)
    0.117035 seconds (11 allocations: 76.294 MiB, 52.56% gc time)
    0.067170 seconds (11 allocations: 76.294 MiB, 76.93% gc time)

我的问题是:

是虫子吗

如果不是bug，那么是否有可能调用完整编译 不，文档明确指出这是由于您在全局范围内运行

@time

：

julia> function foo()
          Test.test(1)  # warm-up
          @time Test.test(10_000_000)
          @time Test.test(10_000_000, hint=true)
          @time Test.test(10_000_000, resize=true)
       end
foo (generic function with 1 method)

julia> foo()
  0.401256 seconds (26 allocations: 129.001 MiB, 47.38% gc time)
  0.185094 seconds (6 allocations: 76.294 MiB, 37.13% gc time)
  0.034649 seconds (6 allocations: 76.294 MiB, 30.99% gc time)

---

感谢您快速而有用的回答！：）将测试明确地包含到功能中有助于解决问题。请您更具体一点，在doc清楚描述此行为的地方复制并粘贴单词好吗？在第二个代码块上方：“作为提示，此函数的改进版本不分配内存（下面报告的分配是由于在全局范围内运行@time宏），并且在第一次调用后执行速度加快了一个数量级：”