Added compilation example

docs/source/usage.rst

@@ -244,3 +244,56 @@ BLAS Examples
 
 Compilation and Linking
 =======================
+To compile with this library, there are only a few things necessary.
+First, it is recommended you use the provided template ``Makefile``, which can be
+easily modified to suit your project needs. It already default handles the compilation
+and linking with ``nvcc``, so long as you fulfill a few requirements.
+
+#. Use the compiler flag ``CUDA`` to mark where GPU-specific code is, if necessary.
+#. Any files that use ``CUDA`` functionality, (i.e defining a kernel), should have the file
+   extension ``.cu.cpp``.
+#. When including the ``Core.h`` header file, in only **one** file, you must define the
+   macro ``CUDATOOLS_IMPLEMENTATION``. That file must also compile for CUDA, so its
+   extension must be ``.cu.cpp``. It's recommended to put this with your kernel definitions.
+
+Afterwards the ``Makefile`` will have two targets ``cpu`` and ``gpu``, which compile
+the CPU and GPU compatible binaries respectively. As an example, we can look at the whole
+file for the first example:
+
+.. code-block:: cpp
+
+    // main.cu.cpp
+    #define CUDATOOLS_IMPLEMENTATION
+    #include <Core.h>
+
+    DEFINE_KERNEL(add, int x, int y) {
+        printf("Kernel: %i\n", x + y);
+    }
+
+    int main() {
+        KERNEL(add, CudaTools::Kernel::basic(1), 1, 1); // Prints 2.
+        return 0;
+    }
+
+.. code-block::
+
+    // Makefile
+
+    CC := g++-10
+    NVCC := nvcc
+    CFLAGS := -Wall -std=c++17 -fopenmp -MMD
+    NVCC_FLAGS := -MMD -w -Xcompiler
+
+    INCLUDE := ../../
+    LIBS_DIR :=
+    LIBS_DIR_GPU := /usr/local/cuda/lib64
+    LIBS :=
+    LIBS_GPU := cuda cudart cublas
+
+    TARGET = coreKernel
+    SRC_DIR = .
+    BUILD_DIR = build
+
+The lines above are the first few lines of the ``Makefile``, which are the only
+lines you should need to modify, consisting of libraries and flags, as well as
+the name of the target.