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Bug #13078

closed
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#1 [ruby-core:78885]

Updated by wanabe (_ wanabe) over 8 years ago

The accuracy of Rational(a, b).to_f seems to be due to reduction of fraction.
How about using Rational object, or its internal function f_gcd() and f_idiv()?

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#2 [ruby-core:78886]

Updated by nobu (Nobuyoshi Nakada) over 8 years ago

I thought the reduction would be slower, but actually not significant.

$ ruby -rbenchmark -e 'a = 3; b = -0x20_0000_0000_0001; n=10_000_000; Benchmark.bm(13) {|x|x.report("Integer#fdiv"){n.times{a.fdiv(b)}}; x.report("Rational#to_f"){n.times{Rational(a, b).to_f}}}'
                    user     system      total        real
Integer#fdiv    3.420000   0.000000   3.420000 (  3.446264)
Rational#to_f   3.450000   0.010000   3.460000 (  3.465592)
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#3

Updated by nobu (Nobuyoshi Nakada) over 8 years ago

  • Status changed from Open to Closed

Applied in changeset r57227.

numeric.c: reduce fdiv

  • numeric.c (rb_int_fdiv_double): reduce first for more precise
    result. [ruby-core:78886] [Bug ]
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#5 [ruby-core:80017]

Updated by naruse (Yui NARUSE) over 8 years ago

  • Backport changed from 2.2: UNKNOWN, 2.3: UNKNOWN, 2.4: UNKNOWN to 2.2: UNKNOWN, 2.3: UNKNOWN, 2.4: DONE

ruby_2_4 r57840 merged revision(s) 57227.

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#6 [ruby-core:80088]

Updated by nagachika (Tomoyuki Chikanaga) over 8 years ago

  • Backport changed from 2.2: UNKNOWN, 2.3: UNKNOWN, 2.4: DONE to 2.2: UNKNOWN, 2.3: REQUIRED, 2.4: DONE
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#7

Updated by usa (Usaku NAKAMURA) over 8 years ago

  • Backport changed from 2.2: UNKNOWN, 2.3: REQUIRED, 2.4: DONE to 2.2: REQUIRED, 2.3: REQUIRED, 2.4: DONE
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