[Numpy-discussion] svd error checking vs. speed

[alex]

On Sat, Feb 15, 2014 at 6:34 PM, Sebastian Berg
<sebastian at sipsolutions.net> wrote:
> On Sa, 2014-02-15 at 18:20 -0500, alex wrote:
> <snip>
>>
>> I'm not sure exactly what you mean by this.  You are suggesting that
>> if the svd fails with some kind of exception (possibly poorly or
>> misleadingly worded) then it could be cleaned-up after the fact by
>> checking the input, and that this would not incur the speed penalty
>> because no check will be done if the svd succeeds?  This would not
>> work on my system because that svd call really does hang, as in some
>> non-ctrl-c-interruptable spin lock inside fortran code or something.
>> I think the behavior is undefined and it can crash although I do not
>> personally have an example of this.  These modes of failure cannot be
>> recovered from as easily as recovering from an exception.
>>
>
> Yeah, I meant that. But it has a big "if", that the failure is basically
> a bug in the library you happen to be using and extremely uncommon.

On my system the lapack bundled with numpy hangs.