Load Dll multiple times to allow multi threading in .Net

Question

My .Net program uses a fortran Dll to perform a maths function (Arpack, solves eigen modes). I believe the fortran contains static varibles and generally isn't thread safe. Also it's very complicated and would probably take a lot of hard work to make it thread safe. The Dll isn't very large (700K) so I just want to load it many times (say 4, or maybe 8) to allow the threads to work concurrently. Anyone have any idea how I can do this? I hear that LoadLibrary will always return the same handle when called multiple times. So, as it stands my only solution is to have multiple copies of my Dll on disk (Arpack1.dll, Arpack2.dll etc) and load them as required. Pretty horrible.

Any ideas?

Euan

Answer 1

The workaround you found is actually a pretty decent one. There might be small odds that LoadLibraryEx() with the LOAD_LIBRARY_AS_IMAGE_RESOURCE option will work. That option allows you to load it multiple times. I seriously doubt it though, the DLL almost certainly relies on getting its runtime support code initialized through DllMain.

One thing I didn't hear you mention is the pain of having to use GetProcAddress(). Make sure you do or you'll still stomp global variables when you start threading. Each thread must use its own address.