Commit 3c2dd5a8 authored by scoder's avatar scoder Committed by GitHub

Merge pull request #2162 from gabrieldemarmiesse/cython_numpy_users

Cython numpy users
parents d5d6508c a171e51a
# cython: infer_types=True
import numpy as np
cimport cython
ctypedef fused my_type:
int
double
long
@cython.boundscheck(False)
@cython.wraparound(False)
cpdef naive_convolve(my_type [:,:] f, my_type [:,:] g):
if g.shape[0] % 2 != 1 or g.shape[1] % 2 != 1:
raise ValueError("Only odd dimensions on filter supported")
vmax = f.shape[0]
wmax = f.shape[1]
smax = g.shape[0]
tmax = g.shape[1]
smid = smax // 2
tmid = tmax // 2
xmax = vmax + 2*smid
ymax = wmax + 2*tmid
if my_type is int:
dtype = np.intc
elif my_type is double:
dtype = np.double
else:
dtype = np.long
h_np = np.zeros([xmax, ymax], dtype=dtype)
cdef my_type [:,:] h = h_np
cdef my_type value
for x in range(xmax):
for y in range(ymax):
s_from = max(smid - x, -smid)
s_to = min((xmax - x) - smid, smid + 1)
t_from = max(tmid - y, -tmid)
t_to = min((ymax - y) - tmid, tmid + 1)
value = 0
for s in range(s_from, s_to):
for t in range(t_from, t_to):
v = x - smid + s
w = y - tmid + t
value += g[smid - s, tmid - t] * f[v, w]
h[x, y] = value
return h_np
\ No newline at end of file
# cython: infer_types=True
import numpy as np
cimport cython
DTYPE = np.intc
@cython.boundscheck(False)
@cython.wraparound(False)
def naive_convolve(int [:,::1] f, int [:,::1] g):
if g.shape[0] % 2 != 1 or g.shape[1] % 2 != 1:
raise ValueError("Only odd dimensions on filter supported")
vmax = f.shape[0]
wmax = f.shape[1]
smax = g.shape[0]
tmax = g.shape[1]
smid = smax // 2
tmid = tmax // 2
xmax = vmax + 2*smid
ymax = wmax + 2*tmid
h_np = np.zeros([xmax, ymax], dtype=DTYPE)
cdef int [:,::1] h = h_np
cdef int value
for x in range(xmax):
for y in range(ymax):
s_from = max(smid - x, -smid)
s_to = min((xmax - x) - smid, smid + 1)
t_from = max(tmid - y, -tmid)
t_to = min((ymax - y) - tmid, tmid + 1)
value = 0
for s in range(s_from, s_to):
for t in range(t_from, t_to):
v = x - smid + s
w = y - tmid + t
value += g[smid - s, tmid - t] * f[v, w]
h[x, y] = value
return h_np
\ No newline at end of file
import numpy as np
DTYPE = np.intc
# It is possible to declare types in the function declaration.
def naive_convolve(int [:,:] f, int [:,:] g):
if g.shape[0] % 2 != 1 or g.shape[1] % 2 != 1:
raise ValueError("Only odd dimensions on filter supported")
# We don't need to check for the type of NumPy array here because
# a check is already performed when calling the function.
cdef Py_ssize_t x, y, s, t, v, w, s_from, s_to, t_from, t_to
cdef Py_ssize_t vmax = f.shape[0]
cdef Py_ssize_t wmax = f.shape[1]
cdef Py_ssize_t smax = g.shape[0]
cdef Py_ssize_t tmax = g.shape[1]
cdef Py_ssize_t smid = smax // 2
cdef Py_ssize_t tmid = tmax // 2
cdef Py_ssize_t xmax = vmax + 2*smid
cdef Py_ssize_t ymax = wmax + 2*tmid
h_np = np.zeros([xmax, ymax], dtype=DTYPE)
cdef int [:,:] h = h_np
cdef int value
for x in range(xmax):
for y in range(ymax):
s_from = max(smid - x, -smid)
s_to = min((xmax - x) - smid, smid + 1)
t_from = max(tmid - y, -tmid)
t_to = min((ymax - y) - tmid, tmid + 1)
value = 0
for s in range(s_from, s_to):
for t in range(t_from, t_to):
v = x - smid + s
w = y - tmid + t
value += g[smid - s, tmid - t] * f[v, w]
h[x, y] = value
return h_np
\ No newline at end of file
from __future__ import division
import numpy as np
def naive_convolve(f, g):
# f is an image and is indexed by (v, w)
# g is a filter kernel and is indexed by (s, t),
# it needs odd dimensions
# h is the output image and is indexed by (x, y),
# it is not cropped
if g.shape[0] % 2 != 1 or g.shape[1] % 2 != 1:
raise ValueError("Only odd dimensions on filter supported")
# smid and tmid are number of pixels between the center pixel
# and the edge, ie for a 5x5 filter they will be 2.
#
# The output size is calculated by adding smid, tmid to each
# side of the dimensions of the input image.
vmax = f.shape[0]
wmax = f.shape[1]
smax = g.shape[0]
tmax = g.shape[1]
smid = smax // 2
tmid = tmax // 2
xmax = vmax + 2*smid
ymax = wmax + 2*tmid
# Allocate result image.
h = np.zeros([xmax, ymax], dtype=f.dtype)
# Do convolution
for x in range(xmax):
for y in range(ymax):
# Calculate pixel value for h at (x,y). Sum one component
# for each pixel (s, t) of the filter g.
s_from = max(smid - x, -smid)
s_to = min((xmax - x) - smid, smid + 1)
t_from = max(tmid - y, -tmid)
t_to = min((ymax - y) - tmid, tmid + 1)
value = 0
for s in range(s_from, s_to):
for t in range(t_from, t_to):
v = x - smid + s
w = y - tmid + t
value += g[smid - s, tmid - t] * f[v, w]
h[x, y] = value
return h
import numpy as np
# We now need to fix a datatype for our arrays. I've used the variable
# DTYPE for this, which is assigned to the usual NumPy runtime
# type info object.
DTYPE = np.intc
def naive_convolve(f, g):
if g.shape[0] % 2 != 1 or g.shape[1] % 2 != 1:
raise ValueError("Only odd dimensions on filter supported")
assert f.dtype == DTYPE and g.dtype == DTYPE
# The "cdef" keyword is also used within functions to type variables. It
# can only be used at the top indentation level (there are non-trivial
# problems with allowing them in other places, though we'd love to see
# good and thought out proposals for it).
# Py_ssize_t is the proper C type for Python array indices.
cdef Py_ssize_t x, y, s, t, v, w, s_from, s_to, t_from, t_to
cdef Py_ssize_t vmax = f.shape[0]
cdef Py_ssize_t wmax = f.shape[1]
cdef Py_ssize_t smax = g.shape[0]
cdef Py_ssize_t tmax = g.shape[1]
cdef Py_ssize_t smid = smax // 2
cdef Py_ssize_t tmid = tmax // 2
cdef Py_ssize_t xmax = vmax + 2*smid
cdef Py_ssize_t ymax = wmax + 2*tmid
h = np.zeros([xmax, ymax], dtype=DTYPE)
# It is very important to type ALL your variables. You do not get any
# warnings if not, only much slower code (they are implicitly typed as
# Python objects).
# For the value variable, we want to use the same data type as is
# stored in the array, so we use int because it correspond to np.intc.
# NB! An important side-effect of this is that if "value" overflows its
# datatype size, it will simply wrap around like in C, rather than raise
# an error like in Python.
cdef int value
for x in range(xmax):
for y in range(ymax):
# Cython has built-in C functions for min and max.
# This makes the following lines very fast.
s_from = max(smid - x, -smid)
s_to = min((xmax - x) - smid, smid + 1)
t_from = max(tmid - y, -tmid)
t_to = min((ymax - y) - tmid, tmid + 1)
value = 0
for s in range(s_from, s_to):
for t in range(t_from, t_to):
v = x - smid + s
w = y - tmid + t
value += g[smid - s, tmid - t] * f[v, w]
h[x, y] = value
return h
\ No newline at end of file
......@@ -56,6 +56,7 @@ To build, run ``python setup.py build_ext --inplace``. Then simply
start a Python session and do ``from hello import say_hello_to`` and
use the imported function as you see fit.
.. _jupyter-notebook:
Using the Jupyter notebook
--------------------------
......
......@@ -59,7 +59,7 @@ that CPython generates for disambiguation, such as
``yourmod.cpython-35m-x86_64-linux-gnu.so`` on a regular 64bit Linux installation
of CPython 3.5.
.. _compiling-distutils:
Compiling with ``distutils``
============================
......
.. _working-numpy:
=======================
Working with NumPy
=======================
......@@ -6,7 +8,7 @@ Working with NumPy
integration described here. They are easier to use than the buffer syntax
below, have less overhead, and can be passed around without requiring the GIL.
They should be preferred to the syntax presented in this page.
See :ref:`Typed Memoryviews <memoryviews>`.
See :ref:`Cython for NumPy users <numpy_tutorial>`.
You can use NumPy from Cython exactly the same as in regular Python, but by
doing so you are losing potentially high speedups because Cython has support
......
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