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Thread: [RESOLVED] Text parser written in VB6 are thousands of times slower than JavaScript.

  1. #1

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    Resolved [RESOLVED] Text parser written in VB6 are thousands of times slower than JavaScript.

    I'm writing a text/lexical parser now. I translated a piece of JavaScript code into VB6 code, and I found that VB6 code was actually thousands of times slower than JavaScript code. I'm extremely shocked. Attached is the test project.

    Note:

    (1) SpeedTest_00 is translated from JavaScript code without any optimization.

    (2) SpeedTest_01 has a simple optimization, which stores Len(oParser.Source) in a variable.

    (3) The test data comes from "http://vbRichClient.com/Downloads/100.zip"

    (4) The test program simply "loops" the chars in the text file. If I add regular expressions to the test project, it will be thousands of times slower than JavaScript.

    I'd like to know how to make VB6 code reach or approach the speed of JavaScript without changing the program structure.

    Any suggestions and solutions would be greatly appreciated.
    Attached Files Attached Files
    Last edited by dreammanor; Mar 2nd, 2020 at 12:58 PM.

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    Re: Text parser written in VB6 are thousands of times slower than JavaScript.

    Can we see the javascript too? Where do you run the .js?

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    Re: Text parser written in VB6 are thousands of times slower than JavaScript.

    I think a copy of your source text is being made from your class property for each CharCodeAt call. If you pass m_sSource instead of oParser.Source, then the speed improves dramatically.

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    Re: Text parser written in VB6 are thousands of times slower than JavaScript.

    Quote Originally Posted by jpbro View Post
    I think a copy of your source text is being made from your class property for each CharCodeAt call.
    Yep, and a second time for each iteration... in SpeedTest_00 (in the Len-call)

    Only VB-For-loops evaluate their "loop-bounds" only once,
    whereas in Do/While loops, the conditions are re-evaluated every time.

    What slows it down in addition, is the call-overhead of all the Method-calls in these loops.

    Quote Originally Posted by jpbro View Post
    If you pass m_sSource instead of oParser.Source, then the speed improves dramatically.
    Yep - the whole looping should better be placed in the Class itself (using its local vars directly).

    If the Class remains as it is (only a Property-Store), then it's better to use an UDT instead.

    Ok, ...just did that with:
    Code:
    Private Type tParser
      Pos As Long
      Source As String
    End Type
    at Form-Level...

    and then simply replaced:
    Dim oParser As tParser
    in the test-routines... no speed-issues anymore...

    Olaf

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    Re: Text parser written in VB6 are thousands of times slower than JavaScript.

    Quote Originally Posted by jpbro View Post
    I think a copy of your source text is being made from your class property for each CharCodeAt call. If you pass m_sSource instead of oParser.Source, then the speed improves dramatically.
    Strange, using m_sSource didn't speed things up when I tried it - had to use a local copy of the string instead (Edit: Because I was thinking about cParser.m_sSource, not the form's m_sSource). Either way, there's a definite problem with ByRef passing of the large string between the form and the class, and it's not obvious why there should be a performance hit. Even if the Property Get is going to return a value, surely there is some native way to return a string out of a class ByRef?
    Last edited by ahenry; Mar 2nd, 2020 at 04:29 PM.

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    Re: Text parser written in VB6 are thousands of times slower than JavaScript.

    Quote Originally Posted by yereverluvinuncleber View Post
    Can we see the javascript too? Where do you run the .js?
    Hi yereverluvinuncleber, here is a simple JavaScript code:
    Code:
    var Parser = function Parser(src) {
        this.pos = 0;
        this.source = String(src);
    }
    
    Parser.prototype.parse = function parse() {
        while (this.pos < this.source.length) {
          var ch = this.source.charCodeAt(this.pos);
          switch (ch) {
          case 32:
            ++this.pos;
            break
          case 13:
            if (this.source.charCodeAt(this.pos + 1) === 10) {
              ++this.pos;
            }
          case 10:
            ++this.pos;
            break
          default:
            ++this.pos;
          }
        }
    }
    
    var s = readFile();
    var p = new Parser(s);
    p.parse();
    I run this js in Chrome. JavaScript is extremely efficient at processing strings, far beyond our imagination.

  7. #7

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    Re: Text parser written in VB6 are thousands of times slower than JavaScript.

    Quote Originally Posted by jpbro View Post
    I think a copy of your source text is being made from your class property for each CharCodeAt call. If you pass m_sSource instead of oParser.Source, then the speed improves dramatically.
    Oh, now I often forget some important knowledge points. Thanks for your reminding, jpbro.

    After replacing oParser.Source with Form1.m_sSource, the speed did increase significantly.

    Quote Originally Posted by ahenry View Post
    Strange, using m_sSource didn't speed things up when I tried it - had to use a local copy of the string instead (Edit: Because I was thinking about cParser.m_sSource, not the form's m_sSource). Either way, there's a definite problem with ByRef passing of the large string between the form and the class, and it's not obvious why there should be a performance hit. Even if the Property Get is going to return a value, surely there is some native way to return a string out of a class ByRef?
    After replacing oParser.Source with Form1.m_sSource, the speed did increase significantly. When cParser.m_sSource is read directly from outside the class, it is still a copy of the string.
    Last edited by dreammanor; Mar 3rd, 2020 at 09:30 PM.

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    Re: Text parser written in VB6 are thousands of times slower than JavaScript.

    Quote Originally Posted by Schmidt View Post
    Yep, and a second time for each iteration... in SpeedTest_00 (in the Len-call)

    Only VB-For-loops evaluate their "loop-bounds" only once,
    whereas in Do/While loops, the conditions are re-evaluated every time.

    What slows it down in addition, is the call-overhead of all the Method-calls in these loops.
    It makes perfect sense, thank you, Olaf.

    Quote Originally Posted by Schmidt View Post
    Yep - the whole looping should better be placed in the Class itself (using its local vars directly).
    The reason I put the whole looping outside the class is mainly to simulate the prototype programming of JavaScript. I want to see if the prototype programming is worth learning from. For example:
    Code:
    var Parser = function Parser(src) {
        this.pos = 0;
        this.source = String(src);
    }
    
    Parser.prototype.parse = function parse() {
        while (this.pos < this.source.length) {
          var ch = this.source.charCodeAt(this.pos);
          switch (ch) {
          case 32:
            ++this.pos;
            break
          case 13:
            if (this.source.charCodeAt(this.pos + 1) === 10) {
              ++this.pos;
            }
          case 10:
            ++this.pos;
            break
          default:
            ++this.pos;
          }
        }
    }
    
    var s = readFile();
    var p = new Parser(s);
    p.parse();
    IMO, the prototype of JavaScript can not only keep Class with only the most basic and core properties, but also leave unlimited possibilities for the future expansion of Class. This is an excellent programming model that is well worth learning. I'd like to know if there are some clever ways to simulate the prototype programming mode of JavaScript. I especially want to hear your suggestions on this question.
    Last edited by dreammanor; Mar 3rd, 2020 at 12:01 PM.

  9. #9

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    Re: Text parser written in VB6 are thousands of times slower than JavaScript.

    Quote Originally Posted by Schmidt View Post
    If the Class remains as it is (only a Property-Store), then it's better to use an UDT instead.

    Ok, ...just did that with:
    Code:
    Private Type tParser
      Pos As Long
      Source As String
    End Type
    at Form-Level...

    and then simply replaced:
    Dim oParser As tParser
    in the test-routines... no speed-issues anymore...
    Yes, using the type tParser seems to be a better option. I'm thinking about whether the structure of my text/lexical should change from "class + module" to "type + module".

  10. #10
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    Re: Text parser written in VB6 are thousands of times slower than JavaScript.

    Quote Originally Posted by dreammanor View Post
    I'd like to know if there are some clever ways to simulate the prototype programming mode of JavaScript.
    It's really hard for "typed" (and compiled) languages, to compete with Scripting
    (which allows much more "degrees of freedom" at runtime).

    To be able to "dynamically extend Function-slots" with "some method, defined in a plain string" -
    that's the realm of Scripting - not of (pre-)compiled languages.

    As for your comment about the JS-StringPerformance...

    You are quite right...
    What the current two "big Browsers" (Firefox and Chrome) deliver there (via their recent "JITers"),
    is "full native speed".

    I thought, with decently optimized VB6-code (native-compiled, with all options),
    we would beat the JS-code you've shown by at least "factor 5 or so" - but no...
    Fully native compiled VB6-code only achieves nearly identical timings - not better ones.

    Here's my performance-test-results (for a single run over the 100.txt file):
    Code:
    Chrome:  23-24msec
    FireFox: 23-24msec
    VB6:     24-25msec
    Edge:    35-36msec
    IE11:   108-110msec
    And here the VB6-Code (after moving the Parse-Method into the cParser-Class):
    Code:
    Option Explicit
    
    Private Declare Sub MemCopy Lib "kernel32" Alias "RtlMoveMemory" (pDst As Any, pSrc As Any, ByVal CB&)
     
    Private this_Pos As Long
    Private this_Lines As Long
    Private this_Words As Long
    Private this_Source() As Integer
    
    Private Sub Class_Initialize()
      ReDim this_Source(0 To 0)
    End Sub
    
    Public Property Get Pos() As Long:    Pos = this_Pos: End Property
    Public Property Let Pos(ByVal RHS As Long): this_Pos = RHS: End Property
    
    Public Property Get Lines() As Long:  Lines = this_Lines: End Property
    Public Property Let Lines(ByVal RHS As Long): this_Lines = RHS: End Property
    
    Public Property Get Words() As Long:  Words = this_Words: End Property
    Public Property Let Words(ByVal RHS As Long): this_Words = RHS: End Property
    
    Public Property Get Source() As String
      If UBound(this_Source) = 0 Then Exit Property
      Source = Space$(UBound(this_Source))
      MemCopy ByVal StrPtr(Source), this_Source(0), LenB(Source)
    End Property
    Public Property Let Source(RHS As String)
      ReDim this_Source(0 To Len(RHS)) 'note, that this allocates one char more than needed, to ensure a zero-char at the end
      Dim pS As Long: pS = StrPtr(RHS)
      If pS Then MemCopy this_Source(0), ByVal pS, LenB(RHS)
    End Property
    
    Public Property Get LenSource() As Long
      LenSource = UBound(this_Source)
    End Property
    
    Public Sub Parse()
        Dim Pos As Long 'a local loop-var is ca 20% faster than using the Private Var: this_Pos
        
        For Pos = 0 To LenSource - 1
            Select Case this_Source(Pos)
               Case 32
                 this_Words = this_Words + 1
               
               Case 13
                 this_Lines = this_Lines + 1
                 'skip the next linefeed-char, if there is one
                 If this_Source(Pos + 1) = 10 Then Pos = Pos + 1
             
               Case 10 'here we only come in, when standalone LF-Chars were used
                 this_Lines = this_Lines + 1
            
               Case Else 'here we do nothing so far...
           
            End Select
        Next
        
        this_Pos = Pos 'reflect this again in this_Pos
    End Sub
    It implements Line- and (rough) Word-Counting (which I've added to the JS-code as well),
    just to ensure that the optimizers were not able to completely "skip" a branch in the select cases.

    Olaf

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    Re: Text parser written in VB6 are thousands of times slower than JavaScript.

    Quote Originally Posted by Schmidt View Post
    It's really hard for "typed" (and compiled) languages, to compete with Scripting
    (which allows much more "degrees of freedom" at runtime).

    To be able to "dynamically extend Function-slots" with "some method, defined in a plain string" -
    that's the realm of Scripting - not of (pre-)compiled languages.

    As for your comment about the JS-StringPerformance...

    You are quite right...
    What the current two "big Browsers" (Firefox and Chrome) deliver there (via their recent "JITers"),
    is "full native speed".
    I understand. Thank you for the explanation, Olaf.

    Quote Originally Posted by Schmidt View Post
    I thought, with decently optimized VB6-code (native-compiled, with all options),
    we would beat the JS-code you've shown by at least "factor 5 or so" - but no...
    Fully native compiled VB6-code only achieves nearly identical timings - not better ones.

    Here's my performance-test-results (for a single run over the 100.txt file):
    Code:
    Chrome:  23-24msec
    FireFox: 23-24msec
    VB6:     24-25msec
    Edge:    35-36msec
    IE11:   108-110msec
    The above test results let me regain my confidence in VB6.

  12. #12

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    Re: Text parser written in VB6 are thousands of times slower than JavaScript.

    Quote Originally Posted by Schmidt View Post
    And here the VB6-Code (after moving the Parse-Method into the cParser-Class):
    Code:
    Option Explicit
    
    Private Declare Sub MemCopy Lib "kernel32" Alias "RtlMoveMemory" (pDst As Any, pSrc As Any, ByVal CB&)
     
    Private this_Pos As Long
    Private this_Lines As Long
    Private this_Words As Long
    Private this_Source() As Integer
    
    Private Sub Class_Initialize()
      ReDim this_Source(0 To 0)
    End Sub
    
    Public Property Get Pos() As Long:    Pos = this_Pos: End Property
    Public Property Let Pos(ByVal RHS As Long): this_Pos = RHS: End Property
    
    Public Property Get Lines() As Long:  Lines = this_Lines: End Property
    Public Property Let Lines(ByVal RHS As Long): this_Lines = RHS: End Property
    
    Public Property Get Words() As Long:  Words = this_Words: End Property
    Public Property Let Words(ByVal RHS As Long): this_Words = RHS: End Property
    
    Public Property Get Source() As String
      If UBound(this_Source) = 0 Then Exit Property
      Source = Space$(UBound(this_Source))
      MemCopy ByVal StrPtr(Source), this_Source(0), LenB(Source)
    End Property
    Public Property Let Source(RHS As String)
      ReDim this_Source(0 To Len(RHS)) 'note, that this allocates one char more than needed, to ensure a zero-char at the end
      Dim pS As Long: pS = StrPtr(RHS)
      If pS Then MemCopy this_Source(0), ByVal pS, LenB(RHS)
    End Property
    
    Public Property Get LenSource() As Long
      LenSource = UBound(this_Source)
    End Property
    
    Public Sub Parse()
        Dim Pos As Long 'a local loop-var is ca 20% faster than using the Private Var: this_Pos
        
        For Pos = 0 To LenSource - 1
            Select Case this_Source(Pos)
               Case 32
                 this_Words = this_Words + 1
               
               Case 13
                 this_Lines = this_Lines + 1
                 'skip the next linefeed-char, if there is one
                 If this_Source(Pos + 1) = 10 Then Pos = Pos + 1
             
               Case 10 'here we only come in, when standalone LF-Chars were used
                 this_Lines = this_Lines + 1
            
               Case Else 'here we do nothing so far...
           
            End Select
        Next
        
        this_Pos = Pos 'reflect this again in this_Pos
    End Sub
    It implements Line- and (rough) Word-Counting (which I've added to the JS-code as well),
    just to ensure that the optimizers were not able to completely "skip" a branch in the select cases.

    Olaf
    Very nice example, which has extremely high performance. Much appreciated.

    Now there is another question: If I put all functions and methods into the Parser class, will the Parser class appear too large? It may have tens of thousands of lines of code. If I distribute these codes into modules, I need to pass the entire Parser object as a function/method parameter, and a copy of the large-string properties will appear.

    One of the benefits of JavaScript prototyping is that it is easy to split a huge object into small modules.
    Last edited by dreammanor; Mar 3rd, 2020 at 11:05 PM.

  13. #13
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    Re: Text parser written in VB6 are thousands of times slower than JavaScript.

    Quote Originally Posted by dreammanor View Post
    Hi yereverluvinuncleber, here is a simple JavaScript code:
    Code:
    Parser.prototype.parse = function parse() {
        while (this.pos < this.source.length) {
          var ch = this.source.charCodeAt(this.pos);
          switch (ch) {
          case 32:
            ++this.pos;
            break
          case 13:
            if (this.source.charCodeAt(this.pos + 1) === 10) {
              ++this.pos;
            }
          case 10:
            ++this.pos;
            break
          default:
            ++this.pos;
          }
        }
    }
    Doesn't this code have the chance of getting caught in an endless loop? If charCodeAt = 13 and then next charCodeAt <> 10 then the loop counter is never updated and you're stuck.

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    Re: Text parser written in VB6 are thousands of times slower than JavaScript.

    Quote Originally Posted by MarkT View Post
    Doesn't this code have the chance of getting caught in an endless loop? If charCodeAt = 13 and then next charCodeAt <> 10 then the loop counter is never updated and you're stuck.
    No, it will get updated in the default-case - due to a "fall-through".
    (case 13 does not contain a break-statement -
    . admittedly easy to miss in these switch-constructs, which I dislike for that reason).

    Here is the adapted JS-TestCode I've used in the different Browser-versions:
    (as html-content ... just place this in a *.html file - and drag it onto the Browser in question):

    Code:
    <html>
    <body> 
    <input type="file" id="fileinp" /> 
    <script>
    
    function readFile() {
        var reader = new FileReader();
            reader.onload = function(){ parsefilecontent(this.result) };
            reader.readAsText(this.files[0]);
    }
    document.getElementById('fileinp').addEventListener('change', readFile);
    
    function parsefilecontent(s){
        var t = performance.now();
        var p = new Parser(s);
            p.parse();
        alert(p.pos +' '+ p.words +' '+ p.lines +' '+ (performance.now()-t))
    }
    
    var Parser = function Parser(src) {
        this.lines = 0;
        this.words = 0;
        this.pos = 0;
        this.source = String(src);
    }
    
    Parser.prototype.parse = function parse() {
        while (this.pos < this.source.length) {
          var ch = this.source.charCodeAt(this.pos);
          switch (ch) {
            case 32:
                ++this.words; //increment the words-counter
                break
            case 13: //handles Mac- and Windows-lineseparators
                ++this.lines; //increment the lines-counter
                //skip the next linefeed-char (if there is one) 
                if (this.source.charCodeAt(this.pos + 1) === 10) ++this.pos;
                break
            case 10: //handles Unix-lineseparators
                ++this.lines; //increment the lines-counter
                break
            default:
                //nothing to do here, so far
          }
          ++this.pos; //better placed outside the switch-block
        }
    }
    
    </script>
    </body>
    </html>
    Olaf

  15. #15

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    Re: Text parser written in VB6 are thousands of times slower than JavaScript.

    After using Olaf's code, the performance of VB6 code has been amazingly improved. The test results are as follows:

    Code:
    JS:  74.535 msec  (Chrome)
    VB6: 31.96 msec

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    Re: Text parser written in VB6 are thousands of times slower than JavaScript.

    Quote Originally Posted by Schmidt View Post
    No, it will get updated in the default-case - due to a "fall-through".
    (case 13 does not contain a break-statement -
    . admittedly easy to miss in these switch-constructs, which I dislike for that reason).
    Yes, I missed no break statement.

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