Update readme.md

readme.md

@@ -15,12 +15,30 @@
 1. Download source code with git by using a command:
 `git clone https://github.com/lchsk/ney.git --recursive`
 
-## Running examples
+(`--recursive` option will download submodules (Google Test, Thrust) into the `thirdparty` directory)
+
+## Compilation
+In order to compile the library, a C++ compiler must be present. Intel C++ Compiler is advised (versions 14 and 15 were used) to exploit all features of the library. For testing purposes, GNU C++ Compiler (`g++`) may be used as well (at least version 4.6.3).
+
+For compiling code for GPUs, please see paragraph `Running examples on GPU`
+
+**Note: the library is designed to work on Linux. Its behaviour on other systems is undefined. Testing was done on the following distributions: Ubuntu 14.04, Scientific Linux 6.3.**
+
+## Running examples on CPU
 1. Enter downloaded directory
 2. `make example`
 3. `cd examples`
 4. Run a selected executable, e.g., `./saxpy`
 
+## Running examples on GPU
+**Note that in order to run anything on the GPU, CUDA toolkit must be installed. It can be downloaded from https://developer.nvidia.com/cuda-toolkit**
+
+1. Enter downloaded directory
+2. `cd examples`
+3. `cd gpu`
+4. `make saxpy`
+4. If you run the executable: `./saxpy`, it will run on the GPU
+
 ## Running tests
 1. Enter downloaded directory
 2. `make && make tests`