Can I use C++ dll through Interop to offload to Xeon Phi?

Question

I read that certain c++ dll can auto - offload to Xeon Phi even if they weren't made specifically to use manycore..

My question - can I Interop a c++ dll built say using Intel parallel studio from c# ? Hoping it will auto-offload

Answer 1

There are DLLs, which can perform automatic offload to Intel Xeon Phi, e.g. Intel MKL. These libraries can be linked with either C++ and C# (see froth's answer).

Automatic offload in this context means that a library contains a code, which allows to offload its computations, transparent to the user.

Also, a library may contain some code, which would decide whether to run the computation on CPU or coprocessor(s).

Answer 2

I am also confused by your statement about dlls being able to auto-offload to the Intel Xeon Phi coprocessor "even if they weren't made specifically to use manycore". To auto-offload, the library must contain code which uses offload directives and is compiled with a compiler that recognizes the offload directives. By default, offload directives result in the compiler generating both processor and coprocessor executable code.

As to how to build a dynamic library containing offload code, let me quote from a reply Kevin Davis posted on the software.intel.com:

For the Dynamic library, all source files containing Language Extensions for Offload must be compiled with the -fPIC compiler option. You add this option under the IDE under the property setting: Configuration Properties > C/C++ > Code Generation [Intel C++] > Additional Options for MIC Offload Compiler .... When using the icl command-line, each source file from the Dynamic library that contains offload code must be compiled using the /Qoffload-option to pass the -fPIC option.

There is a limitation in that you cannot use _Cilk_offload directives in a dll but I think that is the only limitation.

As to calling a library containing offload directive from C#,there is a problem in the Intel® Parallel Studio XE 2015 which is fixed in Update 1. But other than that one version of the compiler, you should be able to call dynamic libraries containing offload directives.