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Math Help - MEX Files

  1. #1
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    MEX Files

    Hi everyone,

    I'm just wondering if somebody can help me out with running a MEX file on MATLAB. The MEX file I would like to run, along with the m file that calls it, is from

    Evan Anderson

    and it's to calculate the generalized ordered schur decomposition for a pair of matrices.

    I save the m file and dll file in the same directory, and when i attempt to run the m file it tells me that the required "process is not found" (referring to the dll file).

    So my question is, do i have to do something to the .dll file before i can call it from an m file? shouldn't it have a .mex extension rather than .dll? or doesn't it matter?


    Thanks guys.

    Brad.
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  2. #2
    Grand Panjandrum
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    Quote Originally Posted by bradbrad View Post
    Hi everyone,

    I'm just wondering if somebody can help me out with running a MEX file on MATLAB. The MEX file I would like to run, along with the m file that calls it, is from

    Evan Anderson

    and it's to calculate the generalized ordered schur decomposition for a pair of matrices.

    I save the m file and dll file in the same directory, and when i attempt to run the m file it tells me that the required "process is not found" (referring to the dll file).

    So my question is, do i have to do something to the .dll file before i can call it from an m file? shouldn't it have a .mex extension rather than .dll? or doesn't it matter?


    Thanks guys.

    Brad.
    Is the directory in the Matlab search path?

    RonL
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  3. #3
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    hi again,

    i checked that the search path was correct, and now i'm getting this error:

    "...schurgaux.dll is not a valid Win32 application."

    Cheers.
    Brad.
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  4. #4
    Grand Panjandrum
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    Quote Originally Posted by bradbrad View Post
    hi again,

    i checked that the search path was correct, and now i'm getting this error:

    "...schurgaux.dll is not a valid Win32 application."

    Cheers.
    Brad.
    Unfortunatly my machines with Matlab installed are not connected to the outside world, so I can't try this out easily.

    The only other suggestion I can think of is that the download did not complete properly and you have a corrupted version of the dll, may be you could try downloading it again (but you probably have already tried that).

    RonL
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  5. #5
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    Thats ok Ron, cheers anyway.

    Matlab actually has in built commands to compute a qz decomposition and to re-order it. So i shouldn't need the dll file anyway. But I cannot get the MATLAB commands to give me the right answer. (I'm trying to replicate something, so I have the answer already.)

    For a pair of matrices, A and B, I would like to find

    B = QTZ'
    A = QSZ'

    where both T and S are upper triangular and QQ' = ZZ' = the identity matrix. The eigenvalues of the system are given by S(i,i)/T(i,i), i.e. the ratio of the corresponding diagonal elements of the two matrices.

    I need the decomposition to be ordered such that

    S(1,1)/T(1,1) < S(2,2)/T(2,2) < ... < S(n,n)/T(n,n).

    MATLAB has a function called ordqz that allows you to reorder a qz decomposition, but I cannot seem to be able to reorder it in such a manner that is consistent with the above, i.e. with the eigenvalues decreasing in absolute value.
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  6. #6
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    I Meant Increasing In Abs Value, Sorry
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