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nexedi
cython
Commits
29c73166
Commit
29c73166
authored
Jun 17, 2018
by
gabrieldemarmiesse
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Moved an example from memoryviews.rst to the examples directory.
parent
5c04c1a8
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53 additions
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-54
docs/examples/userguide/memoryviews/quickstart.pyx
docs/examples/userguide/memoryviews/quickstart.pyx
+52
-0
docs/src/userguide/memoryviews.rst
docs/src/userguide/memoryviews.rst
+1
-54
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docs/examples/userguide/memoryviews/quickstart.pyx
0 → 100644
View file @
29c73166
from
cython.view
cimport
array
as
cvarray
import
numpy
as
np
# Memoryview on a NumPy array
narr
=
np
.
arange
(
27
,
dtype
=
np
.
dtype
(
"i"
)).
reshape
((
3
,
3
,
3
))
cdef
int
[:,
:,
:]
narr_view
=
narr
# Memoryview on a C array
cdef
int
carr
[
3
][
3
][
3
]
cdef
int
[:,
:,
:]
carr_view
=
carr
# Memoryview on a Cython array
cyarr
=
cvarray
(
shape
=
(
3
,
3
,
3
),
itemsize
=
sizeof
(
int
),
format
=
"i"
)
cdef
int
[:,
:,
:]
cyarr_view
=
cyarr
# Show the sum of all the arrays before altering it
print
(
"NumPy sum of the NumPy array before assignments: %s"
%
narr
.
sum
())
# We can copy the values from one memoryview into another using a single
# statement, by either indexing with ... or (NumPy-style) with a colon.
carr_view
[...]
=
narr_view
cyarr_view
[:]
=
narr_view
# NumPy-style syntax for assigning a single value to all elements.
narr_view
[:,
:,
:]
=
3
# Just to distinguish the arrays
carr_view
[
0
,
0
,
0
]
=
100
cyarr_view
[
0
,
0
,
0
]
=
1000
# Assigning into the memoryview on the NumPy array alters the latter
print
(
"NumPy sum of NumPy array after assignments: %s"
%
narr
.
sum
())
# A function using a memoryview does not usually need the GIL
cpdef
int
sum3d
(
int
[:,
:,
:]
arr
)
nogil
:
cdef
size_t
i
,
j
,
k
cdef
int
total
=
0
I
=
arr
.
shape
[
0
]
J
=
arr
.
shape
[
1
]
K
=
arr
.
shape
[
2
]
for
i
in
range
(
I
):
for
j
in
range
(
J
):
for
k
in
range
(
K
):
total
+=
arr
[
i
,
j
,
k
]
return
total
# A function accepting a memoryview knows how to use a NumPy array,
# a C array, a Cython array...
print
(
"Memoryview sum of NumPy array is %s"
%
sum3d
(
narr
))
print
(
"Memoryview sum of C array is %s"
%
sum3d
(
carr
))
print
(
"Memoryview sum of Cython array is %s"
%
sum3d
(
cyarr
))
# ... and of course, a memoryview.
print
(
"Memoryview sum of C memoryview is %s"
%
sum3d
(
carr_view
))
docs/src/userguide/memoryviews.rst
View file @
29c73166
...
...
@@ -28,60 +28,7 @@ Quickstart
If you are used to working with NumPy, the following examples should get you
started with Cython memory views.
::
from cython.view cimport array as cvarray
import numpy as np
# Memoryview on a NumPy array
narr = np.arange(27, dtype=np.dtype("i")).reshape((3, 3, 3))
cdef int [:, :, :] narr_view = narr
# Memoryview on a C array
cdef int carr[3][3][3]
cdef int [:, :, :] carr_view = carr
# Memoryview on a Cython array
cyarr = cvarray(shape=(3, 3, 3), itemsize=sizeof(int), format="i")
cdef int [:, :, :] cyarr_view = cyarr
# Show the sum of all the arrays before altering it
print("NumPy sum of the NumPy array before assignments: %s" % narr.sum())
# We can copy the values from one memoryview into another using a single
# statement, by either indexing with ... or (NumPy-style) with a colon.
carr_view[...] = narr_view
cyarr_view[:] = narr_view
# NumPy-style syntax for assigning a single value to all elements.
narr_view[:, :, :] = 3
# Just to distinguish the arrays
carr_view[0, 0, 0] = 100
cyarr_view[0, 0, 0] = 1000
# Assigning into the memoryview on the NumPy array alters the latter
print("NumPy sum of NumPy array after assignments: %s" % narr.sum())
# A function using a memoryview does not usually need the GIL
cpdef int sum3d(int[:, :, :] arr) nogil:
cdef size_t i, j, k
cdef int total = 0
I = arr.shape[0]
J = arr.shape[1]
K = arr.shape[2]
for i in range(I):
for j in range(J):
for k in range(K):
total += arr[i, j, k]
return total
# A function accepting a memoryview knows how to use a NumPy array,
# a C array, a Cython array...
print("Memoryview sum of NumPy array is %s" % sum3d(narr))
print("Memoryview sum of C array is %s" % sum3d(carr))
print("Memoryview sum of Cython array is %s" % sum3d(cyarr))
# ... and of course, a memoryview.
print("Memoryview sum of C memoryview is %s" % sum3d(carr_view))
.. literalinclude:: ../../examples/userguide/memoryviews/quickstart.pyx
This code should give the following output::
...
...
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