Eric89GXL/scipy — pull request #1 by endolith (2014-07-08 01:44:52+00:00)
Title: ENH: 1st-order sections as 1st-order coefficients

Save a little bit of processing time by throwing away trailing zeros so the 1st-order sections are implemented as actual first-order filters, rather than wasting time multiplying by zeros:

```
x = randn(100000)
sos = array([[ 0.1667, 0.3333, 0.1667, 1. , 0. , 0.3333],
[ 1. , 1. , 0. , 1. , 0. , 0. ]])

timeit sosfilt(sos, x) # original
100 loops, best of 3: 3.12 ms per loop

timeit sosfilt(sos, x) # modified
100 loops, best of 3: 2.6 ms per loop
```

I think defining b and a makes the filtering lines more clear anyway