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Python buffer objects can have negative strides. #782

Merged
merged 4 commits into from
May 7, 2017
Merged

Python buffer objects can have negative strides. #782

merged 4 commits into from
May 7, 2017

Commits on May 3, 2017

  1. Python buffer objects can have negative strides.

    Cris Luengo committed May 3, 2017
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  2. Making a copy when casting a numpy array with negative strides to Eigen. 

    `EigenConformable::stride_compatible` returns false if the strides are
negative. In this case, do not use `EigenConformable::stride`, as it
is {0,0}. We cannot write negative strides in this element, as Eigen
will throw an assertion if we do.

The `type_caster` specialization for regular, dense Eigen matrices now
does a second `array_t::ensure` to copy data in case of negative strides.
I'm not sure that this is the best way to implement this.

I have added "TODO" tags linking these changes to Eigen bug #747, which,
when fixed, will allow Eigen to accept negative strides.
    Cris Luengo committed May 3, 2017
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  3. Use numpy rather than Eigen for copying 

    We're current copy by creating an Eigen::Map into the input numpy
array, then assigning that to the basic eigen type, effectively having
Eigen do the copy.  That doesn't work for negative strides, though:
Eigen doesn't allow them.

This commit makes numpy do the copying instead by allocating the eigen
type, then having numpy copy from the input array into a numpy reference
into the eigen object's data.  This also saves a copy when type
conversion is required: numpy can do the conversion on-the-fly as part
of the copy.

Finally this commit also makes non-reference parameters respect the
convert flag, declining the load when called in a noconvert pass with a
convertible, but non-array input or an array with the wrong dtype.
    @jagerman
    jagerman authored and Cris Luengo committed May 3, 2017
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  4. Now shape, size, ndims and itemsize are also signed integers.

    Cris Luengo committed May 3, 2017
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