Update Install documentation

INSTALL.md

@@ -272,6 +272,43 @@ real and complex valued case, respectively. This can be done with the "--with-fi
 ### Doxygen documentation ###
 A doxygen documentation can be created with the "--enable-doxygen-doc" configure option
 
+### Some examples ###
+
+#### Intel cores supporting AVX2 (Hasell and newer) ####
+
+We recommend that you build ELPA with the Intel compiler (if available) for the Fortran part, but
+with GNU compiler for the C part.
+
+1. Building with Intel Fortran compiler and GNU C compiler:
+
+Remarks: - you have to know the name of the Intel Fortran compiler wrapper
+         - you do not have to specify a C compiler (with CC); GNU C compiler is recognized automatically
+	 - you should specify compiler flags for Intel Fortran compiler; in the example only "-O3 -xAVX2" is set
+	 - you should be carefull with the CFLAGS. The example shows typical flags
+
+FC=wrapper_for_intel_compiler ./configure FCFLAGS="-O3 -xAVX2" CFLAGS="-O3 -march=native -mavx2 -mfma funsafe-loop-optimizations -funsafe-math-optimizations -ftree-vect-loop-version -ftree-vectorize" --enable-option-checking=fatal SCALAPACK_LDFLAGS="L$MKLROOT/lib/intel64 -lmkl_scalapack_lp64 -lmkl_intel_lp64 -lmkl_sequential -lmkl_core -lmkl_blacs_intelmpi_lp64 -lpthread " SCALAPACK_FCFLAGS="-I$MKL_HOME/include/intel64/lp64"
+
+
+2. Building with GNU Fortran compiler and GNU C compiler:
+
+Remarks: - you have to know the name of the GNU Fortran compiler wrapper
+         - you do not have to specify a C compiler (with CC); GNU C compiler is recognized automatically
+	 - you should specify compiler flags for GNU Fortran compiler; in the example only "-O3 -march=native -mavx2 -mfma" is set
+	 - you should be carefull with the CFLAGS. The example shows typical flags
+
+FC=wrapper_for_gnu_compiler ./configure FCFLAGS="-O3 -march=native -mavx2 -mfma" CFLAGS="-O3 -march=native -mavx2 -mfma funsafe-loop-optimizations -funsafe-math-optimizations -ftree-vect-loop-version -ftree-vectorize" --enable-option-checking=fatal SCALAPACK_LDFLAGS="L$MKLROOT/lib/intel64 -lmkl_scalapack_lp64 -lmkl_gf_lp64 -lmkl_sequential -lmkl_core -lmkl_blacs_intelmpi_lp64 -lpthread " SCALAPACK_FCFLAGS="-I$MKL_HOME/include/intel64/lp64"
+
+
+2. Building with Intel Fortran compiler and Intel C compiler:
+
+Remarks: - you have to know the name of the Intel Fortran compiler wrapper
+         - you have to specify the Intel C compiler
+	 - you should specify compiler flags for Intel Fortran compiler; in the example only "-O3 -xAVX2" is set
+	 - you should be carefull with the CFLAGS. The example shows typical flags
+
+FC=wrapper_for_gnu_compiler CC=icc ./configure FCFLAGS="-O3 -xAVX2" CFLAGS="-O3 -xAVX2" --enable-option-checking=fatal SCALAPACK_LDFLAGS="L$MKLROOT/lib/intel64 -lmkl_scalapack_lp64 -lmkl_intel_lp64 -lmkl_sequential -lmkl_core -lmkl_blacs_intelmpi_lp64 -lpthread " SCALAPACK_FCFLAGS="-I$MKL_HOME/include/intel64/lp64"
+
+