20 juillet 2018
What are the architectural differences between R and C++?
From source code to binary
- High level language : the statistician understands and writes "english".
- Low level language: the CPU reads and runs binary (or machine) codes only.
From source code to binary
We need a translator (compiler or interpreter) to go from source to binary code.
Compiler versus interpreter
| The Compiler | The Interpreter | |
|---|---|---|
| Input | takes the entire program and translates it as a whole into machine code. | takes one statement at a time. |
| Workload | runs once and only needs to be called again for re-translation. | runs each time the code needs to be executed. |
| Errors | generates the error message only after scanning the whole program: debugging is hard. | continues translating the program until the first error is met, in which case it stops: debugging is easy. |
| Sharing | harder to share: binary may not be read by different OS, source code must be re-compiled. | easy to share: just pass the source code. |
Compiled language: memory allocation
Because at "compile time", the compiler needs to know exactly what objects are, use of variables is less flexible:
int x; // Construction: allocate
// memory to the object.
x = 15; // Initialisation of
// the object.
x = x + 1; // Do stuff.
~x; // Destruction: clear memory.
// Usually implicit.
How Rcpp goes from C++ to R
