from cpython cimport bool
from cython cimport view
from cython.parallel import prange, parallel
from libc.math cimport sin, cos, abs, floor, round, sqrt
import numpy as np
cimport numpy as npx
cimport cython

__all__=["fast_interp"]


@cython.boundscheck(False)
@cython.cdivision(True)
def fast_interp(npx.float64_t xmin, npx.float64_t dx, npx.float64_t[:] A, npx.float64_t[:] y, npx.float64_t[:] out, npx.float64_t beyond_val=npx.nan):
  cdef double rq, q
  cdef int iq
  cdef long i, Asize, ysize
  cdef npx.float64_t[:] out0

  ysize = y.size
  out0 = out
  Asize = A.size

  with nogil:
    for i in prange(ysize):
      q = (y[i] - xmin) / dx
      iq = int(floor(q))
      rq = (q-iq)
      if iq+1 >= Asize or iq < 0:
        out0[i] = beyond_val
      else:
        out0[i] = rq * A[iq+1] + (1-rq)*A[iq]