8000 BUG: Fix strides of trailing 1s when reshaping by seberg · Pull Request #2950 · numpy/numpy · GitHub
[go: up one dir, main page]
Skip to content

BUG: Fix strides of trailing 1s when reshaping #2950

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 1 commit into from
Feb 28, 2013
Merged

BUG: Fix strides of trailing 1s when reshaping #2950

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
31 changes: 28 additions & 3 deletions numpy/core/src/multiarray/shape.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -355,10 +355,14 @@ _attempt_nocopy_reshape(PyArrayObject *self, int newnd, npy_intp* newdims,
int oldnd;
npy_intp olddims[NPY_MAXDIMS];
npy_intp oldstrides[NPY_MAXDIMS];
npy_intp np, op;
npy_intp np, op, last_stride;
int oi, oj, ok, ni, nj, nk;

oldnd = 0;
/*
* Remove axes with dimension 1 from the old array. They have no effect
* but would need special cases since their strides do not matter.
*/
for (oi = 0; oi < PyArray_NDIM(self); oi++) {
if (PyArray_DIMS(self)[oi]!= 1) {
olddims[oldnd] = PyArray_DIMS(self)[oi];
Expand Down Expand Up @@ -390,27 +394,31 @@ _attempt_nocopy_reshape(PyArrayObject *self, int newnd, npy_intp* newdims,
/* different total sizes; no hope */
return 0;
}
/* the current code does not handle 0-sized arrays, so give up */

if (np == 0) {
/* the current code does not handle 0-sized arrays, so give up */
return 0;
}

/* oi to oj and ni to nj give the axis ranges currently worked with */
oi = 0;
oj = 1;
ni = 0;
nj = 1;
while(ni < newnd && oi < oldnd) {
while (ni < newnd && oi < oldnd) {
np = newdims[ni];
op = olddims[oi];

while (np != op) {
if (np < op) {
/* Misses trailing 1s, these are handled later */
np *= newdims[nj++];
} else {
op *= olddims[oj++];
}
}

/* Check whether the original axes can be combined */
for (ok = oi; ok < oj - 1; ok++) {
if (is_f_order) {
if (oldstrides[ok+1] != olddims[ok]*oldstrides[ok]) {
Expand All @@ -427,6 +435,7 @@ _attempt_nocopy_reshape(PyArrayObject *self, int newnd, npy_intp* newdims,
}
}

/* Calculate new strides for all axes currently worked with */
if (is_f_order) {
newstrides[ni] = oldstrides[oi];
for (nk = ni + 1; nk < nj; nk++) {
Expand All @@ -444,6 +453,22 @@ _attempt_nocopy_reshape(PyArrayObject *self, int newnd, npy_intp* newdims,
oi = oj++;
}

/*
* Set strides corresponding to trailing 1s of the new shape.
*/
if (ni >= 1) {
last_stride = newstrides[ni - 1];
}
else {
last_stride = PyArray_ITEMSIZE(self);
}
if (is_f_order) {
last_stride *= newdims[ni - 1];
}
for (nk = ni; nk < newnd; nk++) {
newstrides[nk] = last_stride;
}

/*
fprintf(stderr, "success: _attempt_nocopy_reshape (");
for (oi=0; oi<oldnd; oi++)
Expand Down
9 changes: 9 additions & 0 deletions numpy/core/tests/test_regression.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -545,6 +545,15 @@ def test_reshape_zero_size(self, level=rlevel):
a = np.ones((0,2))
a.shape = (-1,2)

def test_reshape_trailing_ones_strides(self):
# Github issue gh-2949, bad strides for trailing ones of new shape
a = np.zeros(12, dtype=np.int32)[::2] # not contiguous
strides_c = (16, 8, 8, 8)
strides_f = (8, 24, 48, 48)
assert_equal(a.reshape(3, 2, 1, 1).strides, strides_c)
assert_equal(a.reshape(3, 2, 1, 1, order='F').strides, strides_f)
assert_equal(np.array(0, dtype=np.int32).reshape(1,1).strides, (4,4))

def test_repeat_discont(self, level=rlevel):
"""Ticket #352"""
a = np.arange(12).reshape(4,3)[:,2]
Expand Down
0