Simplify power by integer logic #322
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tompng
commented
May 17, 2025
| @@ -1660,8 +1660,7 @@ def test_limit | |||
| BigDecimal.save_limit do | |||
| BigDecimal.limit(1) | |||
| x = BigDecimal("3") | |||
| assert_equal(90, x ** 4) # OK? must it be 80? | |||
| # 3 * 3 * 3 * 3 = 10 * 3 * 3 = 30 * 3 = 90 ??? | |||
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Before: 3**4 → (3 * (3**2)) * 3 → (3 * 9) * 3 → round(27) * 3 → 90
After: 3**4 → (3 * 3) * (3**2) → 9 * 9 → round(81) → 80
Although this test case seems to be improved, just a coincidence.
This pull request is not a bug fix. Large error still exist.
BigDecimal.limit 1
(BigDecimal('2')**100).to_i / 2**100 #=> 1577
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Refactor and reduce the number of multiplication.
Example calculation of
x**16Calculation of the largest
x**nis dominant. Although multiplication is reduced, the performance improvement is limited.