Re: copymemory basic question

Karl -

I notice you are primarily using VB5 w/SP3. Is this your VB version/SP
combo of choice? And if so, why?

Simply curious. :)

- Kev


"Karl E. Peterson" <karl@xxxxxxxx> wrote in message
news:uZPdWForFHA.2592@xxxxxxxxxxxxxxxxxxxxxxx
> Jim Mack wrote:
>> Karl E. Peterson wrote:
>>>>> I might have an idea on speeding that up a bit...
>>>>
>>>> Just for completeness, there's a DxSwapStr function in Stamina --
>>>> worth seeing how it stacks [cough] up against any VB versions.
>>>
>>> <ahem>
>>>
>>> Well... Yeah, that one pretty well blows away the immediate
>>> competition. Three runs, VB5/SP3, EXE /w all opts:
>>
>> I took a look at the source, and I see that I'm being overly paranoid
>> about what might get passed in. I could cut the code by 1/3 if I
>> could guarantee no null pointers, and I think there may be a way to
>> do that. Probably get down to 75 on your scale.
>>
>> But I'll only do that if you find a way to top it. :-)
>
> I think you got your work cut out for you. Latest results:
>
> Iterations: 10000000
> Overhead: 11
>
> SwapStr01: 3714 (1.000)
> SwapStr02: 1208 (0.325)
> SwapStr03: 1238 (0.333)
> SwapStr04: 1187 (0.320)
> DxSwapStr: 920 (0.248)
> SwapStr05: 592 (0.159)
> SwapStr06: 366 (0.099)
>
> SwapStr01: 3797 (1.000)
> SwapStr02: 1237 (0.326)
> SwapStr03: 1273 (0.335)
> SwapStr04: 1239 (0.326)
> DxSwapStr: 989 (0.260)
> SwapStr05: 640 (0.169)
> SwapStr06: 385 (0.101)
>
> SwapStr01: 3841 (1.000)
> SwapStr02: 1257 (0.327)
> SwapStr03: 1255 (0.327)
> SwapStr04: 1204 (0.313)
> DxSwapStr: 932 (0.243)
> SwapStr05: 612 (0.159)
> SwapStr06: 377 (0.098)
>
> Wanna see the code? <bSEg>
>
> Public Sub SwapStr01(s1 As String, s2 As String)
> Dim tmp As String
> ' Traditional method using pure VB.
> tmp = s1
> s1 = s2
> s2 = tmp
> End Sub
>
> Public Sub SwapStr02(s1 As String, s2 As String)
> Static lpTmp As Long
> ' Basic CopyMemory method that swaps pointers, using
> ' a Static variable for temporary holding space.
> lpTmp = StrPtr(s1)
> Call CopyMemory(ByVal VarPtr(s1), ByVal VarPtr(s2), 4&)
> Call CopyMemory(ByVal VarPtr(s2), lpTmp, 4&)
> End Sub
>
> Public Sub SwapStr03(s1 As String, s2 As String)
> Dim lpTmp As Long
> ' Basic CopyMemory method that swaps pointers, using
> ' a standard variable for temporary holding space.
> lpTmp = StrPtr(s1)
> Call CopyMemory(ByVal VarPtr(s1), ByVal VarPtr(s2), 4&)
> Call CopyMemory(ByVal VarPtr(s2), lpTmp, 4&)
> End Sub
>
> Public Sub SwapStr04(s1 As String, s2 As String)
> Dim ptrStr1 As Long
> Dim ptrVar2 As Long
> ' Enhanced CopyMemory removes one VarPtr call, and
> ' doesn't use Static vars for pointers.
> ptrStr1 = StrPtr(s1)
> ptrVar2 = VarPtr(s2)
> CopyMemory ByVal VarPtr(s1), ByVal ptrVar2, 4&
> CopyMemory ByVal ptrVar2, ptrStr1, 4&
> End Sub
>
> Public Sub SwapStr05(s1 As String, s2 As String)
> Static lpTmp As Long
> ' Use PutMem4 and GetMem4 directly from runtime.
> ' This method requires no typelibs!
> lpTmp = StrPtr(s1)
> 'Call GetMem4(VarPtr(s1), lpTmp)
> Call PutMem4(VarPtr(s1), StrPtr(s2))
> Call PutMem4(VarPtr(s2), lpTmp)
> End Sub
>
> Public Sub SwapStr06(s1 As String, s2 As String)
> Static lpTmp As Long
> ' Use typelib'd versions of PutMem4 and GetMem4.
> lpTmp = AsLng(s1) ' StrPtr(s1)
> AsLng(s1) = AsLng(s2)
> AsLng(s2) = lpTmp
> End Sub
>
> These are the declarations:
>
> ' ** Defined in CopyMem.tlb, to avoid GetLastError overhead
> ' Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory"
> (Destination
> As Any, Source As Any, ByVal Length As Long)
>
> Private Declare Sub GetMem4 Lib "msvbvm50" (ByVal Addr As Long, RetVal
> As Long)
> Private Declare Sub PutMem4 Lib "msvbvm50" (ByVal Addr As Long, ByVal
> NewVal As
> Long)
>
> I'm going to put the typelib out for download, but want to make sure I run
> it through
> its paces first. It was inspired by the work of Michel Rutten at:
>
> http://www.xbeat.net/vbspeed/i_VBVM6Lib.html
>
> In a nutshell, here's what I did for AsLng:
>
> //
> ========================================================================
> // Property AsLng
> //
> ========================================================================
> [
> entry("GetMem4"), propget,
> helpstring("Returns or sets the value referenced by the source parameter
> cast to a
> Long.")
> ]
> HRESULT __stdcall AsLng(
> [in] void * Source,
> [out, retval] long * lpRetVal
> );
>
> [
> entry("PutMem4"), propput
> ]
> HRESULT __stdcall AsLng(
> [in] void * Source,
> [in] long NewValue
> );
>
> I'll follow-up in another venue, with more testing/debugging info.
>
> Thanks... Karl
> --
> Working Without a .NET?
> http://classicvb.org/petition
>
>


.

Relevant Pages

  • Re: copymemory basic question
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  • Re: copymemory basic question
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