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def shellsort(a):
# fixme: remove; obsolete
"""
Shellsort algorithm. Sorts a 1D-array.
Returns: sorted-a, sorting-index-vector (for original array)
Use fastsort for speed.
"""
a = asarray(a)
n = len(a)
svec = a*1.0
ivec = range(n)
gap = n/2 # integer division needed
while gap > 0:
for i in range(gap,n):
for j in range(i-gap,-1,-gap):
while j>=0 and svec[j]>svec[j+gap]:
temp = svec[j]
svec[j] = svec[j+gap]
svec[j+gap] = temp
itemp = ivec[j]
ivec[j] = ivec[j+gap]
ivec[j+gap] = itemp
gap = gap / 2 # integer division needed
# svec is now sorted input vector, ivec has the order svec[i] = vec[ivec[i]]
return array(svec), array(ivec)
def summult(array1, array2, axis=0):
"""
Multiplies elements in array1 and array2, element by element, and
returns the sum (along 'axis',axis=0) of all resulting multiplications.
Axis can equal None (ravel array first), or an integer (the
axis over which to operate),
"""
array1, array2 = map(asarray, (array1, array2))
if axis is None:
array1 = ravel(array1)
array2 = ravel(array2)
axis = 0
return sum(array1*array2,axis)
def sumdiffsquared(a, b, axis=0):
"""
Takes pairwise differences of the values in arrays a and b, squares
these differences, and returns the sum of these squares. Axis
can equal None (ravel array first), an integer (the axis over
which to operate).
Returns: sum[(a-b)**2]
"""
a, b = _chk2_asarray(a, b, axis)
return sum((a-b)**2,axis)
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