Exception message from java: MathLink connection was lost.
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From: Andrey on 8 Feb 2010 07:57 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(a)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
From: David Bailey on 9 Feb 2010 02:48 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(a)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
From: Andrey on 10 Feb 2010 03:37 Dear David Bailey, On Feb 9, 10:48 am, David Bailey <d...(a)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
From: David Bailey on 11 Feb 2010 05:16 Andrey wrote: > Dear David Bailey, > > On Feb 9, 10:48 am, David Bailey <d...(a)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
From: Andrey on 14 Feb 2010 05:58 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...(a)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
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