Known Issues

Compatibility with other installed software


Peregrine users may experience an error on a PC that already has other software installed that uses OpenMP (e.g. Autodesk Monolith):

Solution exception:Unable to load DLL 'LSFORMInterface.dll': The operating system cannot run . (Exception from HRESULT: 0x800700B6)


Other installed software on your system may use a version of the OpenMP library ‘libiomp5md.dll’ which is out of date and does not include functionality that is essential to the correct functioning of Peregrine.



Search your system for instances of ‘libiomp5md.dll’. If there is only one copy that is not in the Peregrine/plugin/win64 folder, then:

  1. Go to the Peregrine plugin folder (likely C:\Program Files\Rhino 6\Plug-ins\Peregrine\plugin\win64)
  2. Locate and copy libiomp5md.dll
  3. Go to the folder with the other copy of libiomp5md.dll and paste over the new version
  4. Start Rhino and then run Peregrine in Grasshopper as normal

If the above does not work, or if you find more than one instance of libiomp5md.dll:

You will need to download the ‘listdlls’ utility from Microsoft. It is a standalone application, so you do not need to install anything. It can be obtained from the link below:

To run it:

  1. Unzip the download to your machine
  2. Ensure that Rhino and Grasshopper (with the Peregrine add-on) are started
  3. Open a command prompt
  4. Navigate in the command prompt to the unzipped folder
  5. Type the command “Listdlls64.exe rhino.exe > dlls.txt” and press enter (quote marks not necessary)
  6. Open dlls.txt in Notepad or similar and search for libiomp5md.dll.
  7. Note (or copy) the path.

Then, without Rhino / Grasshopper running:

  1. Navigate to the path noted in step 7 above.
  2. Locate and rename the file libiomp5md.dll (we recommend calling the file libiomp5md.dll.old or similar)
  3. In a separate explorer, go to the Peregrine plugin folder (likely C:\Program Files\Rhino 6\Plug-ins\Peregrine\plugin\win64)
  4. Locate and copy libiomp5md.dll
  5. Go back to the folder from step 1 and paste in libiomp5md.dll
  6. Start Rhino and then try to run Peregrine in Grasshopper as normal
1 Like