Sample program to create multiple threads

re: Sample program to create multiple threads

Alan Stevens — Fri, 12 May 2006 15:41:18 GMT

Calvin,

This is very cool! Please expand on this in Sedna, so we can launch multiple threads in VFP.

++Alan

re: Sample program to create multiple threads

Janusz Czudek — Mon, 15 May 2006 08:10:00 GMT

Great sample, but can we run a foxpro code on the new thread?

We have to get a pointer (AdrCode) to foxpro procedure/function and pass it to CreateThread()...

Is there a way to get such pointer?

re: Sample program to create multiple threads

Franklin Garón — Mon, 15 May 2006 16:34:19 GMT

Good example, if you put this function as part native of VFP (Sedna), this was great feature.

re: Sample program to create multiple threads

Calvin_Hsia — Mon, 15 May 2006 18:54:19 GMT

Alan, Jausz, Franklin: If you could run VFP code on multiple threads, what scenarios will this enable for you? How will you use it?

thanks

re: Sample program to create multiple threads

Rick Strahl — Tue, 16 May 2006 02:38:39 GMT

Calvin,

I also posted a few .NET examples that do something similar and I actually think that using .NET in that situation is easier. The other advantage of using .NET in thi scenario is that you could call a Visual FoxPro COM component from the multithreaded code - in fact I showed how to do this in a recent article with a generic COM callable .NET component that can execute another COM component which can be VFP created.

http://www.west-wind.com/presentations/dotnetfromVfp/DotNetFromVfp_MultiThreading.asp

Multi-threading can come in very handy in a number of situations. Send and forget operation of a lengthy task. In Web applications Aysnc tasks can be used to fire of a long running task and provide feedback so the Web client can see progress information. Offloading blocking user interfaces (while downloading a file for example) is another where I use multi-threading often...

It would be very cool if there was a way for VFP to create a new thread and then call back into FoxPro code. In fact I seem to remember I played with that a few years ago with the FoxPro library kit, but it wasn't very happy when the call returned on a new thread <g>.

re: Sample program to create multiple threads

Rick Strahl — Tue, 16 May 2006 02:40:46 GMT

BTW, what's the reason for calling LoadLibrary on User32? Isn't that available on the standard Win32API stack already?

re: Sample program to create multiple threads

Calvin_Hsia — Tue, 16 May 2006 04:00:50 GMT

In this sample, LoadLibrary for User32.dll is needed because the return value is passed to GetProcAddress. You’re right that User32.dll is already loaded, so LoadLibrary doesn’t have to *load* the DLL: it just returns the hModule (which is the module address).

See next blog post for sample that calls VFP code in a thread proc.

re: Sample program to create multiple threads

Dimitrios Papadopoulos — Tue, 16 May 2006 13:02:20 GMT

Calvin,

it would be great if you could run fox code in different threads. Actually my scenarios are more or less as Rick's. Here are some scenarios which I would use this option for :
a. I am running a remote - or local - sql query, or queries against several remote databases which at the end the different cursor resultsets must be localy joined. The queries take long because of complexity but the result sets are just a few records ..., asynchronous sqlexec does not help in this case.
b. I have a service that downloads - in a loop - and parses web pages from several different slow web sites. In order to proceed to the next download the program has to wait the previous ...
c. There are issues with timers also that can be improoved by using multithreading. To be able to have different timers in an application that run code at the same time...

re: Sample program to create multiple threads

Jochen Kirstaetter — Tue, 16 May 2006 18:47:59 GMT

Thanks for this article, Calvin.
Threading is very powerful and as Rick already stated in his comment as well as in his blog articles. Threading in VFP would be very productive in case of long-term processes. We have several customer projects with huge data processing - monthly/quarterly/yearly billing runs - with about 1.5GB data. So, if the customer starts this process the machine is blocked for approx. 2 hours (depending on the number of clients being processed). So, if we could fork those runs on a separate thread, it would be a lot easier for us *not to block* the application and just show an indicator on a dialog or status bar.

Same for background downloads and other stuff like this.

So, in my opinion Threading would be a boost for VFP! Today I'm using a .NET based launcher for COM servers like Rick. But a native solution would be more interesting.

Kind regards, JoKi

Create multiple threads from within your application

Calvin Hsia's WebLog — Tue, 16 May 2006 21:01:25 GMT

When I posted this Sample program to create multiple threads, I knew the inevitable follow-up question...

re: Sample program to create multiple threads

Franklin Garzón — Wed, 17 May 2006 05:50:36 GMT

If, the colleagues have exposed the principal points for which to implement the MH in VFP as a native part, another case is that nowadays on having executed a process of connection to a WS the machine freezes waiting for the process of response.

re: Sample program to create multiple threads

Craig Larson — Wed, 17 May 2006 20:06:54 GMT

I'm wondering if the majority of users just need a box message to pop up informing them that some process is happening and will be available shortly, would this not be a simpler solution?

** C++ code below **

#include "pro_ext.h"
#include <string.h>

char FAR mmsg[254];

DWORD WINAPI FAR Message(LPVOID aVoidPointer)
{
MessageBox(NULL, mmsg, "Separate Thread Support",NULL);
return (0);
}

void FAR mbox(ParamBlk FAR *parm) // the function definition
{
DWORD ThreadId;

char FAR *msg;

msg = ((char FAR *) _HandToPtr(parm->p[0].val.ev_handle));

strncpy(mmsg, msg, strlen(msg));

CreateThread(NULL,0, Message, 0, 0, &ThreadId); //show messagebox in separate thread
_RetLogical(1); //return .T.
}

FoxInfo myFoxInfo[] ={
{"MBOX", (FPFI) mbox, 1, "C"},
};

extern "C" FoxTable _FoxTable = {
(FoxTable FAR *)0, sizeof(myFoxInfo)/ sizeof(FoxInfo), myFoxInfo
};

** Fox Code Below **
SET LIBRARY TO meep
_result = .F.

_result = mbox("Messagebox in separate thread")

FOR _cnt = 1 TO 5
WAIT WINDOW "Count = " + STR(_cnt) TIMEOUT 1
ENDFOR

IF (_result)
WAIT WINDOW "MessageBox Was Displayed" nowait
ENDIF

re: Sample program to create multiple threads

Olaf Doschke — Fri, 19 May 2006 02:44:05 GMT

This is nice in showing, that MT is even possible with some API calls. But the last time I poked some assembler into memory was with the commodore vc 20, not even c64, even with that oldie one could use an assembler :^).

How would we use MT within VFP?

1. using API calls with a callback function like MoveFileWithProgress().

2. nonblocking wait for external processes: Multiple file download, mail sending, COM port polling, whatever.
Especially in case of the failure of an external process, with a separate thread a timeout is much easier, and that thread may die without affecting the main thread.

3. putting lengthy porcesses in the background, like backup of large amounts of files, lenghty complex queries (datamining).

4. seperating tasks into smaller portions being able to run parallel in principle.
For example with shared memory access, one thread may fill a buffer by reading in a file, one thread may process it (eg compress blocks), the next thread writes the processed data back to disk.
All this may be done step by step in a single thread, but seperating these three tasks could make use of multiple cpu cores and balance cpu needs.

5.,6.,7.,8.,9.,... what I even did not think about now.

Bye, Olaf.

re: Sample program to create multiple threads

Martin Bauer — Fri, 19 May 2006 12:40:56 GMT

I need threading in VFP !

re: Sample program to create multiple threads

DOUGBAKER — Thu, 25 May 2006 05:13:40 GMT

Well, I recently upgraded my workstation to a fast processor with hyper threading. When I run some processes, one virtual processor is maxed, the other one is not doing much. If I could create multiple threads, my hunch is the processor would use hyper threading to run both threads. If I can design the threads to not be dependent on each other, would I get faster throughput?

re: Sample program to create multiple threads

Calvin_Hsia — Thu, 25 May 2006 22:40:46 GMT

DougBaker: yes: with hyperthreading or with multiprocessors, throughput can be much improved when there is little interthread resource contention

re: Sample program to create multiple threads

meimeib — Wed, 14 Jun 2006 10:44:13 GMT

hi,Calvin_Hsia ^_^
can you demo this code with vfp's form instead of messageboxA?
thank you
meimeib@126.com

re: Sample program to create multiple threads

jimsun — Sat, 18 Nov 2006 23:04:30 GMT

Calvin,

can you tell me how to run a EXE in a thread!

re: Sample of easy programs of foxpro with problems

noel — Thu, 23 Nov 2006 10:22:23 GMT

can you give me an easy sample of database programs with problems and foxpro with problems i ned it for my project.......... just send to this e-mail guitarsound_music@yahoo.com thanks im hoping for your rply as soon as posible thank you.....

re: Sample program to create multiple threads

yothinin — Thu, 15 Feb 2007 17:14:48 GMT

Hi, Calvin

I need to run VFP's form look like !!meimeib!!. Can you tell me more.

Thanks advance

yothinin@hotmail.com

How to interrupt your code

Calvin Hsia's WebLog — Fri, 16 May 2008 05:43:19 GMT

I received a question: Simply, is there a way of interrupting a vfp sql query once it has started short

re: Sample program to create multiple threads

raja — Sun, 18 May 2008 15:35:16 GMT

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re: Sample program to create multiple threads

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re: Sample program to create multiple threads

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re: Sample program to create multiple threads

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re: Sample program to create multiple threads

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re: Sample program to create multiple threads

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Компьютерная помощь

logginnoff — Fri, 21 Aug 2009 06:50:11 GMT

Привет

Помогите плиз, комп не включается, синий экран и всё :(

Компьютерная помощь приезжали, винды переустановили - непомогает

сейчас снова синий экран :((

Комп не трогал, все так и было...

Или хотя бы куда обратится в Москве? Чтобы недорого..

Спасибо заранее!