# [NumPy-Tickets] [NumPy] #2027: einsum/iterator bug

NumPy Trac numpy-tickets@scipy....
Sat Jan 21 17:39:45 CST 2012

```#2027: einsum/iterator bug
------------------------+---------------------------------------------------
Reporter:  mwiebe      |       Owner:  somebody
Type:  defect      |      Status:  new
Priority:  high        |   Milestone:  1.7.0
Component:  numpy.core  |     Version:  1.6.1
Keywords:              |
------------------------+---------------------------------------------------
This was reported by royf by reopening ticket #1885. I'm moving it to a
new ticket, as it's a new bug, even though it's very similar in nature to
the one reopened.

Problem not solved in 1.6.1, or a very similar problem remains:

import numpy; print(numpy.version.full_version); a = numpy.arange(1, 3); b
= numpy.arange(1, 5).reshape(2, 2); c = numpy.arange(1, 9).reshape(4, 2);
numpy.einsum('x,yx,zx->xzy', a, b, c)

1.6.1 array([[[ 1, 3],

[ 3, 9], [ 1, 3], [ 3, 9]],

[[ 8, 16],

[16, 32], [ 8, 16], [16, 32]]])

The correct result is

numpy.array([[[a[x]*b[y, x]*c[z, x] for y in range(2)] for z in range(4)]
for x in range(2)])

array([[[ 1, 3],

[ 3, 9], [ 5, 15], [ 7, 21]],

[[ 8, 16],

[16, 32], [24, 48], [32, 64]]])

--
Ticket URL: <http://projects.scipy.org/numpy/ticket/2027>
NumPy <http://projects.scipy.org/numpy>
My example project
```