— Function: size_t gsl_interp_bsearch (const double x_array[], double x, size_t index_lo, size_t index_hi)

This function returns the index i of the array x_array such that x_array[i] <= x < x_array[i+1]. The index is searched for in the range [index_lo,index_hi]. An inline version of this function is used when HAVE_INLINE is defined.

— Function: gsl_interp_accel * gsl_interp_accel_alloc (void)

This function returns a pointer to an accelerator object, which is a kind of iterator for interpolation lookups. It tracks the state of lookups, thus allowing for application of various acceleration strategies.

— Function: size_t gsl_interp_accel_find (gsl_interp_accel * a, const double x_array[], size_t size, double x)

This function performs a lookup action on the data array x_array of size size, using the given accelerator a. This is how lookups are performed during evaluation of an interpolation. The function returns an index i such that x_array[i] <= x < x_array[i+1]. An inline version of this function is used when HAVE_INLINE is defined.

— Function: int gsl_interp_accel_reset (gsl_interp_accel * acc);

This function reinitializes the accelerator object acc. It should be used when the cached information is no longer applicable—for example, when switching to a new dataset.

— Function: void gsl_interp_accel_free (gsl_interp_accel* acc)

This function frees the accelerator object acc.