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Exception message from java: MathLink connection was lost.

Hello,

I wrote a java program (which runs some calculation on math kernel)
with JLink interface but it crashes regularly and randomly with the
exception:
"Exception message: MathLink connection was lost.
Exception class: com.wolfram.jlink.MathLinkException
Exception cause: null".

My system: winXP(prof), Mathematica 7.0.1.

I decided that the problem is with JLinkNativeLibrary.dll (which loads
during JLink load) and I recompile it for my machine (the only
warnings were the followings:
"JLinkNativeLibrary.c: In function
`Java_com_wolfram_jlink_NativeLink_getNativeWindowHandle':
JLinkNativeLibrary.c:1910: warning: cast from pointer to integer of
different size
JLinkNativeLibrary.c: In function
`Java_com_wolfram_jlink_NativeLink_appToFront':
JLinkNativeLibrary.c:1960: warning: cast to pointer from integer of
different size
....\MINGW\bin\..\lib\gcc\mingw32\3.4.5\..\..\..\..\mingw32\bin\ld.exe:
warning: cannot find entry symbol _DllMainCRTStartup@12; defaulting to
6bf81000").
But problem remains.
Then I tried to recompile the JLink.jar (and after that recompile
JLinkNativeLibrary.dll again) with no success.

Did anybody meet such the problem?

Or could anybody suggest anything or help?


Regards,

-Andrey



0
2/8/2010 12:57:57 PM
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Andrey wrote:
> Hello,
> 
> I wrote a java program (which runs some calculation on math kernel)
> with JLink interface but it crashes regularly and randomly with the
> exception:
> "Exception message: MathLink connection was lost.
> Exception class: com.wolfram.jlink.MathLinkException
> Exception cause: null".
> 
> My system: winXP(prof), Mathematica 7.0.1.
> 
> I decided that the problem is with JLinkNativeLibrary.dll (which loads
> during JLink load) and I recompile it for my machine (the only
> warnings were the followings:
> "JLinkNativeLibrary.c: In function
> `Java_com_wolfram_jlink_NativeLink_getNativeWindowHandle':
> JLinkNativeLibrary.c:1910: warning: cast from pointer to integer of
> different size
> JLinkNativeLibrary.c: In function
> `Java_com_wolfram_jlink_NativeLink_appToFront':
> JLinkNativeLibrary.c:1960: warning: cast to pointer from integer of
> different size
> ...\MINGW\bin\..\lib\gcc\mingw32\3.4.5\..\..\..\..\mingw32\bin\ld.exe:
> warning: cannot find entry symbol _DllMainCRTStartup@12; defaulting to
> 6bf81000").
> But problem remains.
> Then I tried to recompile the JLink.jar (and after that recompile
> JLinkNativeLibrary.dll again) with no success.
> 
> Did anybody meet such the problem?
> 
> Or could anybody suggest anything or help?
> 
> 
> Regards,
> 
> -Andrey
> 
> 
> 
I use J/Link a lot, and I have not encountered this problem. The most 
likely explanation, I think, is that your Java program breaks in some 
catastrophic way or loops indefinitely. If it is feasible, I would try 
compiling your Java code with a main method and try to test it as a 
free-standing Java program. I would also re-install the DLL files from 
the Mathematica installation disk, just in case your recompilation 
introduced any further issues.

David Bailey
http://www.dbaileyconsultancy.co.uk

0
dave2659 (542)
2/9/2010 7:48:27 AM
Dear David Bailey,

On Feb 9, 10:48 am, David Bailey <d...@removedbailey.co.uk> wrote:
> ...
> I use J/Link a lot, and I have not encountered this problem. The most
> likely explanation, I think, is that your Java program breaks in some
> catastrophic way or loops indefinitely.

Yes, it can be so, but the same java code works ok on some others
systems (I knew two of them, one was winXP and other was Linux).

It looks like there is a problem with transition of floating-point
numbers from Mathematica to java...

I will try to transfer only strings...

> If it is feasible, I would try
> compiling your Java code with a main method and try to test it as a
> free-standing Java program. I would also re-install the DLL files from
> the Mathematica installation disk, just in case your recompilation
> introduced any further issues.

I've been working in such a way.

>
> David Bailey http://www.dbaileyconsultancy.co.uk

Thank You for the answer.

Regards,

-Andrey

0
2/10/2010 8:37:29 AM
Andrey wrote:
> Dear David Bailey,
> 
> On Feb 9, 10:48 am, David Bailey <d...@removedbailey.co.uk> wrote:
>> ...
>> I use J/Link a lot, and I have not encountered this problem. The most
>> likely explanation, I think, is that your Java program breaks in some
>> catastrophic way or loops indefinitely.
> 
> Yes, it can be so, but the same java code works ok on some others
> systems (I knew two of them, one was winXP and other was Linux).
> 
> It looks like there is a problem with transition of floating-point
> numbers from Mathematica to java...
> 
> I will try to transfer only strings...
> 
>> If it is feasible, I would try
>> compiling your Java code with a main method and try to test it as a
>> free-standing Java program. I would also re-install the DLL files from
>> the Mathematica installation disk, just in case your recompilation
>> introduced any further issues.
> 
> I've been working in such a way.
> 
>> David Bailey http://www.dbaileyconsultancy.co.uk
> 
> Thank You for the answer.
> 
> Regards,
> 
> -Andrey
> 
A good way to explore this problem might be to call ShowJavaConsole[] to 
produce a console, and then add calls to

System.out.println(whatever)

in your Java code.

Mathematica Real's correspond to Java's double's - other than that, 
there should be no problem transferring floating point quantities, but 
if you generate NaN's, there could be problems, I don't know.

David Bailey
http://www.dbaileyconsultancy.co.uk


David Bailey
http://www.dbaileyconsultancy.co.uk

0
dave2659 (542)
2/11/2010 10:16:25 AM
The problem appears after

ml.waitForAnswer();

(where ml is KernelLink).

The stack trace shows that exception arise in class
com.wolfram.jlink.NativeLink in the following method:
....
	public synchronized int nextPacket() throws MathLinkException {

		if (link == 0) {
			throw new MathLinkException(MLE_LINK_IS_NULL, LINK_NULL_MESSAGE);
		}
		int pkt = MLNextPacket(link); // <-- Probably Here
		int errCode = MLError(link);
		if(errCode == 0) {
			return pkt;
		} else {
			throw new MathLinkException(errCode, MLErrorMessage(link));
		}
	}
....
So, it looks like the problem is in native library.

Of course, probably, it's possible to avoid the problem by rewriting
the mathematica code...

-Andrey

On Feb 11, 1:16 pm, David Bailey <d...@removedbailey.co.uk> wrote:

> A good way to explore this problem might be to call ShowJavaConsole[] to
> produce a console, and then add calls to
>
> System.out.println(whatever)
>
> in your Java code.

I do not understand now how to do it and how it can help.

But thanks for the suggestion.

-Andrey

0
2/14/2010 10:58:34 AM
Finally, the problem have been solved. It comes out that we used
obsolete protocol (TCP instead of TCPIP or SharedMemory).

Regards,

-Andrey

0
2/14/2010 1:17:32 PM
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