add MKL to README

README.md

@@ -60,15 +60,23 @@ You can read about [getting started](https://julialang.org/manual/getting-started
 <a name="Platform-Specific-Notes"/>
 ### Platform-Specific Notes
 
+#### Linux
+
 On some Linux distributions you may need to change how the readline library is linked. If you get a build error involving readline, try changing the value of `USE_SYSTEM_READLINE` in `Make.inc` to `1`.
 
-On Ubuntu, you may also need to install the package `libncurses5-dev`.
+#### Ubuntu
+
+You may also need to install the package `libncurses5-dev`.
 
-On OS X, you may need to install `gfortran`. Either download and install [gfortran from hpc.sf.net](https://hpc.sf.net/), or [64-bit gfortran from gcc.gnu.org](https://gcc.gnu.org/wiki/GFortranBinaries).
+#### OS X
+
+You may need to install `gfortran`. Either download and install [gfortran from hpc.sf.net](https://hpc.sf.net/), or [64-bit gfortran from gcc.gnu.org](https://gcc.gnu.org/wiki/GFortranBinaries).
 
 If you get link errors mentioning `gfortran`, it might help to put `/usr/local/gfortran/lib` at the beginning of the `DYLD_LIBRARY_PATH` environment variable.
 
-On FreeBSD the prerequisites can be installed from ports like this:
+#### FreeBSD
+
+The prerequisites can be installed from ports like this:
 
  cd /usr/ports/devel/gmake
  make install
@@ -87,6 +95,15 @@ Other versions of gcc are also exist but currently gfortran45 is the one used by
 
 **Use the gmake command on FreeBSD instead of make**
 
+#### MKL
+
+To use the Intel [MKL] BLAS & LAPACK libraries, edit the following settings in `Make.inc`:
+
+ USE_MKL = 1
+ MKLLIB = /path/to/mkl/lib/arch
+
+`MKLLIB` points to the directory containing `libmkl_rt.so`. Requires v10.3 or greater.
+
 <a name="Required-Build-Tools-External-Libraries"/>
 ## Required Build Tools & External Libraries
 
@@ -109,6 +126,7 @@ Julia uses the following external libraries, which are automatically downloaded
 - **[MT]** — a fast Mersenne Twister pseudorandom number generator library.
 - **[OpenBLAS]** — a fast, open, and maintained [basic linear algebra subprograms (BLAS)](https://en.wikipedia.org/wiki/Basic_Linear_Algebra_Subprograms) library, based on [Kazushige Goto's](https://en.wikipedia.org/wiki/Kazushige_Goto) famous [GotoBLAS](https://www.tacc.utexas.edu/tacc-projects/gotoblas2/).
 - **[LAPACK]** — a library of linear algebra routines for solving systems of simultaneous linear equations, least-squares solutions of linear systems of equations, eigenvalue problems, and singular value problems.
+- (optional) **[MKL]** -- OpenBLAS & LAPACK may be replaced by Intel's MKL library.
 - **[AMOS]** — subroutines for computing Bessel and Airy functions.
 - **[SuiteSparse]** — a library of linear algebra routines for sparse matrices.
 - **[ARPACK]** — a collection of subroutines designed to solve large, sparse eigenvalue problems.
@@ -129,6 +147,7 @@ Julia uses the following external libraries, which are automatically downloaded
 [MT]: https://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html
 [OpenBLAS]: https://github.com/xianyi/OpenBLAS#readme
 [LAPACK]: https://www.netlib.org/lapack/
+[MKL]: https://software.intel.com/en-us/articles/intel-mkl/
 [SuiteSparse]: https://www.cise.ufl.edu/research/sparse/SuiteSparse/
 [AMOS]: https://netlib.org/amos
 [ARPACK]: https://forge.scilab.org/index.php/p/arpack-ng/