深入探讨用位掩码代替分支(6):VB6速度测试
前面我们测试了C系列语言,验证了位掩码算法的确实性能不错。那么对于Basic系列语言,该算法的效率怎样呢?于是本文对此进行探讨。 一、移植要点 VB6的功能与C系列语言差很多。很多地方需要换另一种方法去实现,甚至不能实现。
全部代码—— ' Win32 API Private Declare Function timeGetTime Lib "winmm.dll" () As Long ' 数据规模 Private Const DATASIZE As Long = 16384 ' 128KB / (sizeof(signed short) * 4) ' 缓冲区 Private bufS(0 To DATASIZE * 4 - 1) As Integer ' 源缓冲区。64位的颜色(4通道,每通道16位) Private bufD(0 To DATASIZE * 4 - 1) As Byte ' 目标缓冲区。32位的颜色(4通道,每通道8位) ' 用if分支做饱和处理 Private Sub f0_if(ByRef pbufD() As Byte,ByRef pbufS() As Integer,ByVal cnt As Long) Dim i As Long Dim p As Long ' 当前位置 p = 0 For i = 0 To cnt - 1 ' 分别对4个通道做饱和处理 If pbufS(p) < 0 Then pbufD(p) = 0 Else If pbufS(p) > 255 Then pbufD(p) = 255 Else pbufD(p) = pbufS(p) p = p + 1 If pbufS(p) < 0 Then pbufD(p) = 0 Else If pbufS(p) > 255 Then pbufD(p) = 255 Else pbufD(p) = pbufS(p) p = p + 1 If pbufS(p) < 0 Then pbufD(p) = 0 Else If pbufS(p) > 255 Then pbufD(p) = 255 Else pbufD(p) = pbufS(p) p = p + 1 If pbufS(p) < 0 Then pbufD(p) = 0 Else If pbufS(p) > 255 Then pbufD(p) = 255 Else pbufD(p) = pbufS(p) p = p + 1 Next i End Sub ' 用IIF函数做饱和处理 Private Sub f1_iif(ByRef pbufD() As Byte,ByVal cnt As Long) Dim i As Long Dim p As Long ' 当前位置 p = 0 For i = 0 To cnt - 1 ' 分别对4个通道做饱和处理 pbufD(p) = IIf(pbufS(p) < 0,IIf(pbufS(p) > 255,255,pbufS(p))) p = p + 1 pbufD(p) = IIf(pbufS(p) < 0,pbufS(p))) p = p + 1 Next i End Sub ' 用位掩码做饱和处理.用求负生成掩码 Private Sub f2_neg(ByRef pbufD() As Byte,ByVal cnt As Long) Dim i As Long Dim p As Long ' 当前位置 p = 0 For i = 0 To cnt - 1 ' 分别对4个通道做饱和处理 pbufD(p) = ((pbufS(p) And (pbufS(p) >= 0) Or (pbufS(p) >= 256)) And &HFF) p = p + 1 pbufD(p) = ((pbufS(p) And (pbufS(p) >= 0) Or (pbufS(p) >= 256)) And &HFF) p = p + 1 pbufD(p) = ((pbufS(p) And (pbufS(p) >= 0) Or (pbufS(p) >= 256)) And &HFF) p = p + 1 pbufD(p) = ((pbufS(p) And (pbufS(p) >= 0) Or (pbufS(p) >= 256)) And &HFF) p = p + 1 Next i End Sub Private Function LIMITSU_BYTE(ByVal n As Integer) As Byte LIMITSU_BYTE = ((n And (n >= 0) Or (n >= 256)) And &HFF) End Function ' 调用LIMITSU_BYTE函数 Private Sub f2_negB(ByRef pbufD() As Byte,ByVal cnt As Long) Dim i As Long Dim p As Long ' 当前位置 p = 0 For i = 0 To cnt - 1 ' 分别对4个通道做饱和处理 pbufD(p) = LIMITSU_BYTE(pbufS(p)) p = p + 1 pbufD(p) = LIMITSU_BYTE(pbufS(p)) p = p + 1 pbufD(p) = LIMITSU_BYTE(pbufS(p)) p = p + 1 pbufD(p) = LIMITSU_BYTE(pbufS(p)) p = p + 1 Next i End Sub Private Sub OutLog(ByRef s As String) txtOut.Text = txtOut.Text & s & Chr(13) & Chr(10) txtOut.Refresh DoEvents ' 响应界面事件 End Sub ' 进行测试 Private Sub runTest(ByVal bFull As Boolean) Const MaxI As Long = 3 ' 多次测试 Const MaxJ As Long = 4000 ' 重复运算几次延长时间,避免计时精度问题 Dim tm0 As Long,tm1 As Long ' 执行时 间 Dim i As Long,j As Long ' begin btnTest.Enabled = False btnTestFull.Enabled = False txtOut.Text = "" Call OutLog("== noif:VB6 ==") ' f0_if For i = 1 To MaxI ' 多次测试 tm0 = timeGetTime() For j = 1 To MaxJ ' 重复运算几次延长时间,避免计时精度问题 Call f0_if(bufD,bufS,DATASIZE) Next j tm1 = timeGetTime() - tm0 Call OutLog("f0_if[" & i & "]:" & Chr(9) & tm1) Next i ' f1_iif If bFull Then For i = 1 To MaxI ' 多次测试 tm0 = timeGetTime() For j = 1 To MaxJ ' 重复运算几次延长时间,避免计时精度问题 Call f1_iif(bufD,DATASIZE) Next j tm1 = timeGetTime() - tm0 Call OutLog("f1_iif[" & i & "]:" & Chr(9) & tm1) Next i End If ' f2_neg For i = 1 To MaxI ' 多次测试 tm0 = timeGetTime() For j = 1 To MaxJ ' 重复运算几次延长时间,避免计时精度问题 Call f2_neg(bufD,DATASIZE) Next j tm1 = timeGetTime() - tm0 Call OutLog("f2_neg[" & i & "]:" & Chr(9) & tm1) Next i ' f2_negB For i = 1 To MaxI ' 多次测试 tm0 = timeGetTime() For j = 1 To MaxJ ' 重复运算几次延长时间,避免计时精度问题 Call f2_negB(bufD,DATASIZE) Next j tm1 = timeGetTime() - tm0 Call OutLog("f2_negB[" & i & "]:" & Chr(9) & tm1) Next i ' end btnTest.Enabled = True btnTestFull.Enabled = True End Sub Private Sub btnTest_Click() Call runTest(False) btnTest.SetFocus End Sub Private Sub btnTestFull_Click() Call runTest(True) btnTestFull.SetFocus End Sub Private Sub Form_Load() Dim i As Long ' 初始化 Randomize For i = 0 To DATASIZE * 4 - 1 bufS(i) = CInt(Rnd() * 512) - 128 ' 使数值在 [-128,383] 区间 Next i Exit Sub End Sub Private Sub Form_Resize() ' 是文本框自适应窗口尺寸 Call txtOut.Move(0,txtOut.Top,Me.ScaleWidth,Me.ScaleHeight - txtOut.Top) End Sub Private Sub Form_Unload(Cancel As Integer) ' End Sub
3.1 配置编译优化 步骤如下——
获取编译器生成的汇编代码有助于分析程序性能。虽然VB6集成开发环境没有提供该功能,但可以通过替换“C2.exe”来获得汇编代码。详见——
虽然可以在开发环境中按F5运行,但它实际上是以解释方式运行的。 四、测试结果 运行编译后的“noifVB6.exe”。在32位winXP上的测试结果—— == noif:VB6 == f0_if[1]: 2844 f0_if[2]: 2859 f0_if[3]: 2844 f1_iif[1]: 83422 f1_iif[2]: 83453 f1_iif[3]: 83422 f2_neg[1]: 1078 f2_neg[2]: 1063 f2_neg[3]: 1078 f2_negB[1]: 2125 f2_negB[2]: 2125 f2_negB[3]: 2140
在64位win7上的测试结果—— == noif:VB6 == f0_if[1]: 2839 f0_if[2]: 2824 f0_if[3]: 2839 f1_iif[1]: 90137 f1_iif[2]: 90137 f1_iif[3]: 90199 f2_neg[1]: 1061 f2_neg[2]: 1061 f2_neg[3]: 1061 f2_negB[1]: 2090 f2_negB[2]: 2090 f2_negB[3]: 2090
硬件环境——
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