Inventor API代码性能优化 - 1

好久没写Inventor方面的专题了。最近我们团队专家Brian写了篇很有深度的文章Improving Your Program’s Performance，专门谈到如何对Inventor API代码性能优化。借此机会翻译概要，供给各位参考。

首先，最好对性能有个量化的评估，到底有多慢。可以使用开发语言中的秒表。例如.NET里有StopWatch。

' Use the .Net StopWatch class to time an action. 
Dim stopwatch As New System.Diagnostics.Stopwatch 
stopwatch.Start()

' Do some things. 
' Get the time taken. 
MessageBox.Show("Elapsed time: " & _ 
                stopwatch.ElapsedMilliseconds / 1000 & " seconds")

VBA中有方法，但Brian实践中发现有时这个方法不能返回正确的时间。他一般用这个自定义类，例如名为 clsTimer

' clsTimer Definition. 
Private Declare PtrSafe Function QueryPerformanceFrequency _ 
         Lib "kernel32" (lpFrequency As Currency) As LongPtr 
Private Declare PtrSafe Function QueryPerformanceCounter _ 
         Lib "kernel32" (lpPerformanceCount As Currency) As LongPtr

Private ConversionFactor As Currency 
Private CurrentStartTime As Currency

Public Sub Start() 
    Dim iReturn As LongPtr 
    iReturn = QueryPerformanceCounter(CurrentStartTime) 
End Sub

Public Function GetTime() As Double 
    Dim NewTime As Currency 
    Dim iReturn As LongPtr 
    iReturn = QueryPerformanceCounter(NewTime) 
    
    Dim TotalTime As Currency 
    TotalTime = NewTime - CurrentStartTime 
    GetTime = TotalTime / ConversionFactor 
End Function

Private Sub Class_Initialize() 
    Dim iReturn As LongPtr 
    iReturn = QueryPerformanceFrequency(ConversionFactor) 
End Sub

接着您就可以用这个类来计算时间：

' Use the timer class to time an action. 
Dim timer As New clsTimer 
timer.Start 

' Do some things. 

' Get the time taken. 
MsgBox "Elapsed time: " & Format(timer.GetTime, "0.00000") & " seconds"

其实，在琢磨消耗时间之前，大前提是，您的应用程序是Inventor进程内的（插件）还是进程外（独立的EXE）。这里有个小测试，反复调用一个Inventor方法，进程内消耗0.24秒，进程外需要74.8秒。

Public Sub CallCost() 
    Dim timer As New clsTimer 
    timer.Start 

    Dim i As Long 
    For i = 1 To 100000 
        Dim code As Long 
        code = ThisApplication.Locale 
    Next 

    Debug.Print "Total time: " & Format(timer.GetTime, "0.00000") 
End Sub

当然上面的测试并不是简单的说进程内比进程外总是快74.8/0.24 = 312倍。但总体上，大多数场景，进程内比进程外要快，所以，如果您的是独立EXE，可考虑是否做成插件。学徒服务器也是独立EXE，它的调用效率要比单纯的启动Inventor的独立EXE要快些。

但有时我们不得不用进程外的方式，例如计划任务批处理，或者是一个Excel里的VBA宏，跨进程调用。那么我们还得从代码本身想想办法。

进程内比进程外要快些，其中一个因素是进程外把配置用户界面（Ribbon)消耗和其它调用分开，并且Ribbon的调用优先级较高。而进程外内的是把二者纳入到进程本身。可以通过设置UserInterfaceManager.UserInteractionDisabled 为true让程序不处理Ribbon方面的功能，尤其对于进程外的操作，一般不会和Inventor本身界面打交道。Brian测试发现，上面的压力测试，从78.4秒将变为61.32 秒，而且好些程序过程都有明显的提升。

Public Sub CallCost() 
    Dim timer As New clsTimer 
    timer.Start 

    app.UserInterfaceManager.UserInteractionDisabled = True 

    Dim i As Long 
    For i = 1 To 100000 
        Dim code As Long 
        code = ThisApplication.Locale 
    Next 

    app.UserInterfaceManager.UserInteractionDisabled = False 

    Debug.Print "Total time: " & Format(timer.GetTime, "0.00000") 
End Sub

注意做一些异常和错误的判断，及时恢复UserInteractionDisabled = false，避免因此造成其它环节的问题。