If your native code takes more than a few seconds to finish, it is a nice courtesy to the user to check for user interrupts (Ctrl-C) once in a while, say, every 1,000 or 1,000,000 iteration. The C-level API of R provides R_CheckUserInterrupt() for this (see ‘Writing R Extensions’ for more information on this function). Here’s what the code would typically look like:
for (int ii = 0; ii < n; ii++) { /* Some computational expensive code */ if (ii % 1000 == 0) R_CheckUserInterrupt() } This uses the modulo operator % and tests when it is zero, which happens every 1,000 iteration.
