Yibo Cai created ARROW-11758: -------------------------------- Summary: [C++][Compute] Summation kernel round-off error Key: ARROW-11758 URL: https://issues.apache.org/jira/browse/ARROW-11758 Project: Apache Arrow Issue Type: Bug Reporter: Yibo Cai
>From below test, summation kernel is of lower precision than numpy.sum. Numpy implements pairwise summation [1] with O(logn) round-off error, better than O(n) error from naive summation. *sum.py* {code:python} import numpy as np import pyarrow.compute as pc t = np.arange(321000, dtype='float64') t2 = t - np.mean(t) t2 *= t2 print('numpy sum:', np.sum(t2)) print('arrow sum:', pc.sum(t2)) {code} *test result* {noformat} # Verified with wolfram alpha (arbitrary precision), Numpy's result is correct. $ ARROW_USER_SIMD_LEVEL=SSE4_2 python sum.py numpy sum: 2756346749973250.0 arrow sum: 2756346749973248.0 $ ARROW_USER_SIMD_LEVEL=AVX2 python sum.py numpy sum: 2756346749973250.0 arrow sum: 2756346749973249.0 {noformat} [1] https://en.wikipedia.org/wiki/Pairwise_summation -- This message was sent by Atlassian Jira (v8.3.4#803005)