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I am trying to write a User subroutine (UMAT) for the concrete Microplane model in ABAQUS. The UMAT was written in Fortran. In order to compute the eigenvalues of a non-symmetric matrix, DGEEV was called in the Fortran file. But it did not work as I expected and ended up getting the following error. Can someone explain why DGEEV is not identified by Fortran?

Unresolved external symbol "DGEEV" referenced in function
Vladimir F Героям слава
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Thushara
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  • DGEEV is a function/subroutine from either BLAS or LAPACK (don't docs handy to determine which). You'll need to add -lblas and/or -llapack -lblas to your command line. – steve Mar 29 '21 at 01:20
  • [`dgeev`](http://www.math.utah.edu/software/lapack/lapack-d/dgeev.html) is part of lapack. You need to show us your compilation/linking commands. My first guess would be that you don't link against lapack. – jack Mar 29 '21 at 06:55
  • Welcome, please take the [tour] and read [ask]. Do **not** upload any pictures with error messages or code. It is completely unacceptable, error messages must be readable by everyone and searchable. Copy and paste all errors and codes **as text**. If you have any error message, you must show the command that caused it. – Vladimir F Героям слава Mar 29 '21 at 07:27
  • We absolutely do need a canonical duplicate target similar to the C++ one https://stackoverflow.com/questions/12573816/what-is-an-undefined-reference-unresolved-external-symbol-error-and-how-do-i-fix – Vladimir F Героям слава Mar 29 '21 at 07:32
  • @jack We probably could. Or we could have many answers, that is not a problem. – Vladimir F Героям слава Mar 29 '21 at 08:10
  • @Jack, yes, you are correct. I did not link against lapack. can you guide me on how to do that? I am new to Fortran Subroutines – Thushara Apr 01 '21 at 05:55
  • @Thushara You can find more about how to resolve this issue by reading the [answers to that question](https://stackoverflow.com/q/66855252/10774817). – jack Apr 01 '21 at 06:58
  • Does this answer your question? [What is an undefined reference/unresolved external symbol error and how do I fix it in Fortran?](https://stackoverflow.com/questions/66855252/what-is-an-undefined-reference-unresolved-external-symbol-error-and-how-do-i-fix) – jack Apr 01 '21 at 06:58
  • @Jack, It discusses the reasons why this error appears. I tried to find a way to install lapack on windows (as I am using windows) as given on this site http://icl.cs.utk.edu/lapack-for-windows/lapack/, but it didn't work. – Thushara Apr 16 '21 at 03:55

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