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How to get time elapsed in milliseconds

Since string concatenation performance is pretty weak in VB6, I am testing several StringBuilder implementations. To find out how long they work, I currently use the built-in

Timer

which gives me only the number of seconds elapsed after midnight.

Is there a way (I think importing a system function) to get something accurate to the millisecond?

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8 answers

Yes, you can use the Win32 API:

DWORD WINAPI GetTickCount(void);

To import it into VB6, declare it as follows:

Private Declare Function GetTickCount Lib "kernel32" () As Long

Call it before the operation, and then and then calculate the time difference.

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:

Option Explicit

Private Declare Function QueryPerformanceCounter Lib "Kernel32" (X As Currency) As Boolean
Private Declare Function QueryPerformanceFrequency Lib "Kernel32" (X As Currency) As Boolean

Private m_startTime As Currency
Private m_freq As Currency
Private m_overhead As Currency

Public Sub start()
    QueryPerformanceCounter m_startTime
End Sub

Public Function ElapsedSeconds() As Double
    Dim currentTime As Currency
    QueryPerformanceCounter currentTime
    ElapsedSeconds = (currentTime - m_startTime - m_overhead) / m_freq
End Function

Public Function ElapsedMilliseconds() As Double
    ElapsedMilliseconds = ElapsedSeconds * 1000
End Function

Private Sub Class_Initialize()
    QueryPerformanceFrequency m_freq
    Dim ctr1 As Currency
    Dim ctr2 As Currency
    QueryPerformanceCounter ctr1
    QueryPerformanceCounter ctr2
    m_overhead = ctr2 - ctr1
End Sub

:

Dim sw as StopWatch
sw = New StopWatch
sw.Start

' Code you want to time

Debug.Print "Code took " & sw.ElapsedMilliseconds " ms"
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. , .

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API Win32:

LARGE_INTEGER 64- .

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MSDN KB Q172338 QueryPerformanceCounter

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1000 . = .

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- ( , ). :

Option Explicit

Private Declare Function QueryPerformanceFrequency Lib "kernel32" (lpFrequency As Currency) As Long
Private Declare Function QueryPerformanceCounter Lib "kernel32" (lpPerformanceCount As Currency) As Long

Private cFrequency As Currency
Private cCounters(0 To 5) As Currency

Public Sub StartCounter(Optional lCounterIndex As Long)
    QueryPerformanceFrequency cFrequency
    QueryPerformanceCounter cCounters(lCounterIndex)
End Sub

Public Function GetCounter(Optional lCounterIndex As Long) As Double
    Dim cCount As Currency

    QueryPerformanceFrequency cFrequency
    QueryPerformanceCounter cCount
    GetCounter = Format$((cCount - cCounters(lCounterIndex) - CCur(0.0008)) / cFrequency, "0.000000000")
End Function

Public Function Scientific(ByVal dValue As Double) As String
    Dim lMultiplier As Long
    Dim vNames As Variant

    lMultiplier = 5
    vNames = Array("peta", "tera", "giga", "mega", "kilo", "", "milli", "micro", "nano", "pico", "femto")
    If Abs(dValue) < 1 Then
        While Abs(dValue) < 1
            dValue = dValue * 1000
            lMultiplier = lMultiplier + 1
        Wend
    ElseIf Abs(dValue) >= 1000 Then
        While Abs(dValue) >= 1000
            dValue = dValue / 1000
            lMultiplier = lMultiplier - 1
        Wend
    End If

    Scientific = Format$(dValue, "0.000") & " " & vNames(lMultiplier)
End Function
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System:: Diagnostics:: Stopwatch

Imports System.Diagnostics

Dim sw As New Stopwatch()
sw.Start()
// do something
LOG("Elapsed " + sw.ElapsedMilliseconds + " ms")
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