Use absolute tolerance for sum_of_poly kernel #654
Merged
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Fixes #650.
The "sum of poly" kernel output is the sum of many positive & negative values, and the final sum can end up being close to zero. This causes test failures, because the relative error becomes large when the sum is near zero. Here I've switched to an absolute tolerance. I tested the generic kernel against a double-precision implementation and found that the error can be as high as 120 (which isn't surprising, since 131071 * 5 = 655355 polynomial terms are summed), so I set the tolerance at 1000 to keep it a safe distance away.