Question

这是我成为程序员7年后的第一篇关于堆栈溢出的文章。我有一个非常愚蠢的问题。两者之间哪个更有效？ C ++或C＃编译器会自动对其进行优化吗？如果是，它将更改为什么？

hadoop --cluster your-hadoop-cluster fs -ls /path/your_hive_table_path/ | grep '/path/your_hive_table_path/' | while read line
do
   #Get the update date of hive table
   date_str=`echo $line | awk -F'[ ]+' '{print $6}'`
   #get the path of hive table
   table_path=`echo $line | awk -F'[ ]+' '{print $8}'`
   #Get the table name of hive table
   table_name=`echo $table_path | awk -F'/' '{print $7}' `

   today_date_stamp=`date +%s`
   table_date_stamp=`date -d $date_str +%s`
   stamp_diff=`expr $today_date_stamp - $table_date_stamp`

   #Get the diff days from now
   days_diff=`expr $stamp_diff / 86400`

   #if diff days is greater than 90, rm and drop.
   if [ $days_diff -gt 90 ];then
      #remove the hdfs file
      hadoop --cluster your-hadoop-cluster fs -rm $table_path
      #drop the hive table
      hive -e"drop table $table_name"
   fi
done

Answer 1

在C＃的发布模式下，它们都编译为相同的IL

.class private auto ansi '<Module>'
{
} // end of class <Module>

.class public auto ansi beforefieldinit C
    extends [mscorlib]System.Object
{
    // Methods
    .method public hidebysig 
        instance void M (
            bool a
        ) cil managed 
    {
        // Method begins at RVA 0x2050
        // Code size 3 (0x3)
        .maxstack 8

        IL_0000: ldarg.1
        IL_0001: pop
        IL_0002: ret
    } // end of method C::M

    .method public hidebysig specialname rtspecialname 
        instance void .ctor () cil managed 
    {
        // Method begins at RVA 0x2054
        // Code size 7 (0x7)
        .maxstack 8

        IL_0000: ldarg.0
        IL_0001: call instance void [mscorlib]System.Object::.ctor()
        IL_0006: ret
    } // end of method C::.ctor

} // end of class C

在Debug Configuration（调试配置）中，b==a和// Methods .method public hidebysig instance void M ( bool a ) cil managed { // Method begins at RVA 0x2050 // Code size 9 (0x9) .maxstack 1 .locals init ( [0] bool, [1] bool ) IL_0000: nop IL_0001: ldarg.1 IL_0002: stloc.1 // sequence point: hidden IL_0003: ldloc.1 IL_0004: brfalse.s IL_0008 IL_0006: ldarg.1 IL_0007: stloc.0 IL_0008: ret } // end of method C::M之间有很小的区别（消除噪声）；参见IL_0006行。

// Methods
.method public hidebysig 
    instance void M (
        bool a
    ) cil managed 
{
    // Method begins at RVA 0x2050
    // Code size 9 (0x9)
    .maxstack 1
    .locals init (
        [0] bool,
        [1] bool
    )

    IL_0000: nop
    IL_0001: ldarg.1
    IL_0002: stloc.1
    // sequence point: hidden
    IL_0003: ldloc.1
    IL_0004: brfalse.s IL_0008

    IL_0006: ldc.i4.1
    IL_0007: stloc.0

    IL_0008: ret
} // end of method C::M

和b == true版本

document.getElementById('button4').addEventListener('click', function(){
    document.getElementById('box').style.height = null;
    document.getElementById('box').style.background = null;
    document.getElementById('box').style.opacity = null;
}

在实践中，在担心这种微观优化之前，我希望先对您的确切用法进行基准测试。花费在优化工作上的时间不可能是最有价值的。

哪种检查方法比设置值最合适？

1 个答案: