#define PETSC_DESIRE_FEATURE_TEST_MACROS /* for usleep()  */
#include <petscsys.h>                    /*I   "petscsys.h"    I*/
#if defined(PETSC_HAVE_UNISTD_H)
  #include <unistd.h>
#endif
#if defined(PETSC_HAVE_DOS_H) /* borland */
  #include <dos.h>
#endif
#if defined(PETSC_HAVE_TIME_H)
  #include <time.h>
#endif

/*@
  PetscSleep - Sleeps some number of seconds.

  Not Collective

  Input Parameter:
. s - number of seconds to sleep

  Level: intermediate

  Note:
  If `s` is negative waits for keyboard input

.seealso: `PetscTime()`
@*/
PetscErrorCode PetscSleep(PetscReal s)
{
  PetscFunctionBegin;
  if (s < 0) getc(stdin);

  /* Some systems consider it an error to call nanosleep or usleep for more than one second so we only use them for subsecond sleeps. */
#if defined(PETSC_HAVE_NANOSLEEP)
  else if (s < 1) {
    struct timespec rq;
    rq.tv_sec  = 0;
    rq.tv_nsec = (long)(s * 1e9);
    nanosleep(&rq, NULL);
  }
#elif defined(PETSC_HAVE_USLEEP)
  /* POSIX.1-2001 deprecates this in favor of nanosleep because nanosleep defines interaction with signals */
  else if (s < 1) usleep((unsigned int)(s * 1e6));
#endif

#if defined(PETSC_HAVE_SLEEP)
  else
    sleep((int)s);
#elif defined(PETSC_HAVE__SLEEP) && defined(PETSC_HAVE__SLEEP_MILISEC)
  else _sleep((int)(s * 1000));
#elif defined(PETSC_HAVE__SLEEP)
  else _sleep((int)s);
#else
  SETERRQ(PETSC_COMM_SELF, PETSC_ERR_SUP_SYS, "No support for sleep() on this machine");
#endif
  PetscFunctionReturn(PETSC_SUCCESS);
}