iframe-proxy | Sunbelt Computer Software

495 lines (447 loc) · 23.3 KB
# SOME DESCRIPTIVE TITLE.
# Copyright (C) 2001-2022, Python Software Foundation
# This file is distributed under the same license as the Python package.
# Translators:
# yichung279, 2018
# cypevan, 2018
# Adrian Liaw <adrianliaw2000@gmail.com>, 2018
# Steven Hsu <hsuhaochun@gmail.com>, 2021
"Project-Id-Version: Python 3.12\n"
"Report-Msgid-Bugs-To: \n"
"POT-Creation-Date: 2023-07-17 17:39+0800\n"
"PO-Revision-Date: 2023-06-22 14:43+0800\n"
"Last-Translator: Matt Wang <mattwang44@gmail.com>\n"
"Language-Team: Chinese - TAIWAN (https://github.com/python/python-docs-zh-"
"Language: zh_TW\n"
"MIME-Version: 1.0\n"
"Content-Type: text/plain; charset=UTF-8\n"
"Content-Transfer-Encoding: 8bit\n"
"Plural-Forms: nplurals=1; plural=0;\n"
"X-Generator: Poedit 3.3.1\n"
#: ../../tutorial/floatingpoint.rst:10
msgid "Floating Point Arithmetic:  Issues and Limitations"
msgstr "浮點數運算：問題與限制"
#: ../../tutorial/floatingpoint.rst:16
"Floating-point numbers are represented in computer hardware as base 2 "
"(binary) fractions.  For example, the **decimal** fraction ``0.625`` has "
"value 6/10 + 2/100 + 5/1000, and in the same way the **binary** fraction "
"``0.101`` has value 1/2 + 0/4 + 1/8. These two fractions have identical "
"values, the only real difference being that the first is written in base 10 "
"fractional notation, and the second in base 2."
"在計算機架構中，浮點數 (floating-point number) 是以基數為 2（二進位）的小數表"
"示。例如說，在\\ **十進位**\\ 小數中 ``0.625`` 可被分為 6/10 + 2/100 + "
"5/1000，同樣的道理，\\ **二進位**\\ 小數 ``0.101`` 可被分為 1/2 + 0/4 + 1/8。"
"這兩個小數有相同的數值，而唯一真正的不同在於前者以十進位表示，後者以二進位表"
#: ../../tutorial/floatingpoint.rst:23
"Unfortunately, most decimal fractions cannot be represented exactly as "
"binary fractions.  A consequence is that, in general, the decimal floating-"
"point numbers you enter are only approximated by the binary floating-point "
"numbers actually stored in the machine."
"不幸的是，大多數十進位小數無法精準地以二進位小數表示。一般的結果為，你輸入的"
"十進位浮點數只能由實際儲存在計算機中的二進位浮點數近似。"
#: ../../tutorial/floatingpoint.rst:28
"The problem is easier to understand at first in base 10.  Consider the "
"fraction 1/3.  You can approximate that as a base 10 fraction::"
"在十進位中，這個問題更容易被理解。以分數 1/3 為例，你可以將其近似為十進位小"
#: ../../tutorial/floatingpoint.rst:33 ../../tutorial/floatingpoint.rst:37
msgid "or, better, ::"
"或者，更好的近似：\n"
#: ../../tutorial/floatingpoint.rst:41
"and so on.  No matter how many digits you're willing to write down, the "
"result will never be exactly 1/3, but will be an increasingly better "
"approximation of 1/3."
"依此類推，不論你使用多少位數表示小數，最後的結果都無法精準地表示 1/3，但你還"
"是能越來越精準地表示 1/3。"
#: ../../tutorial/floatingpoint.rst:45
"In the same way, no matter how many base 2 digits you're willing to use, the "
"decimal value 0.1 cannot be represented exactly as a base 2 fraction.  In "
"base 2, 1/10 is the infinitely repeating fraction ::"
"同樣的道理，不論你願意以多少位數表示二進位小數，十進位小數 0.1 都無法被二進位"
"小數精準地表達。在二進位小數中，1/10 會是一個無限循環小數：\n"
#: ../../tutorial/floatingpoint.rst:51
"Stop at any finite number of bits, and you get an approximation.  On most "
"machines today, floats are approximated using a binary fraction with the "
"numerator using the first 53 bits starting with the most significant bit and "
"with the denominator as a power of two.  In the case of 1/10, the binary "
"fraction is ``3602879701896397 / 2 ** 55`` which is close to but not exactly "
"equal to the true value of 1/10."
"只要你停在任何有限的位數，你就只會得到近似值。而現在大多數的計算機中，浮點數"
"是透過二進位分數近似的，其中分子是從最高有效位元開始，用 53 個位元表示，分母"
"則是以二為底的指數。在 1/10 的例子中，二進位分數為 ``3602879701896397 / 2 ** "
"55``，而這樣的表示十分地接近，但不完全等同於 1/10 的真正數值。"
#: ../../tutorial/floatingpoint.rst:58
"Many users are not aware of the approximation because of the way values are "
"displayed.  Python only prints a decimal approximation to the true decimal "
"value of the binary approximation stored by the machine.  On most machines, "
"if Python were to print the true decimal value of the binary approximation "
"stored for 0.1, it would have to display::"
"由於數值顯示的方式，很多使用者並沒有發現數值是個近似值。Python 只會印出一個十"
"進位近似值，其近似了儲存在計算機中的二進位近似值的真正十進位數值。在大多數的"
"計算機中，如果 Python 真的會印出完整的十進位數值，其表示儲存在計算機中的 0.1 "
"的二進位近似值，它將顯示為：\n"
#: ../../tutorial/floatingpoint.rst:67
"That is more digits than most people find useful, so Python keeps the number "
"of digits manageable by displaying a rounded value instead:"
"這比一般人感到有用的位數還多，所以 Python 將位數保持在可以接受的範圍，只顯示"
#: ../../tutorial/floatingpoint.rst:75
"Just remember, even though the printed result looks like the exact value of "
"1/10, the actual stored value is the nearest representable binary fraction."
"一定要記住，雖然印出的數字看起來是精準的 1/10，但真正儲存的數值是能表示的二進"
"位分數中，最接近精準數值的數。"
#: ../../tutorial/floatingpoint.rst:78
"Interestingly, there are many different decimal numbers that share the same "
"nearest approximate binary fraction.  For example, the numbers ``0.1`` and "
"``0.10000000000000001`` and "
"approximated by ``3602879701896397 / 2 ** 55``.  Since all of these decimal "
"values share the same approximation, any one of them could be displayed "
"while still preserving the invariant ``eval(repr(x)) == x``."
"有趣的是，有許多不同的十進位數，共用同一個最接近的二進位近似分數。例如說：數"
"字 ``0.1`` 和 ``0.10000000000000001`` 和 "
"``3602879701896397 / 2 ** 55`` 近似。由於這三個十進位數值共用同一個近似值，任"
"何一個數值都可以被顯示，同時保持 ``eval(repr(x)) == x``。"
#: ../../tutorial/floatingpoint.rst:86
"Historically, the Python prompt and built-in :func:`repr` function would "
"choose the one with 17 significant digits, ``0.10000000000000001``.   "
"Starting with Python 3.1, Python (on most systems) is now able to choose the "
"shortest of these and simply display ``0.1``."
"歷史上，Python 的提示字元 (prompt) 與內建的 :func:`repr` 函式會選擇上段說明中"
"有 17 個有效位元的數：``0.10000000000000001``。從 Python 3.1 版開始，Python"
"（在大部分的系統上）現在能選擇其中最短的數並簡單地顯示為 ``0.1``。"
#: ../../tutorial/floatingpoint.rst:91
"Note that this is in the very nature of binary floating-point: this is not a "
"bug in Python, and it is not a bug in your code either.  You'll see the same "
"kind of thing in all languages that support your hardware's floating-point "
"arithmetic (although some languages may not *display* the difference by "
"default, or in all output modes)."
"注意，這是二進位浮點數理所當然的特性，並不是 Python 的錯誤 (bug)，更不是你程"
"式碼的錯誤。只要程式語言有支援硬體的浮點數運算，你將會看到同樣的事情出現在其"
"中（雖然有些程式語言預設不會\\ *顯示*\\ 該差異，有些甚至是在所有的輸出模式中"
#: ../../tutorial/floatingpoint.rst:97
"For more pleasant output, you may wish to use string formatting to produce a "
"limited number of significant digits:"
"為求更優雅的輸出，你可能想要使用字串的格式化 (string formatting) 產生限定的有"
#: ../../tutorial/floatingpoint.rst:111
"It's important to realize that this is, in a real sense, an illusion: you're "
"simply rounding the *display* of the true machine value."
"要了解一件很重要的事，在真正意義上，浮點數的表示是一種幻覺：你基本上在捨入真"
"正機器數值所\\ *展示的值*。"
#: ../../tutorial/floatingpoint.rst:114
"One illusion may beget another.  For example, since 0.1 is not exactly 1/10, "
"summing three values of 0.1 may not yield exactly 0.3, either:"
"這種幻覺可能會產生下一個幻覺。舉例來說，因為 0.1 不是真正的 1/10，把三個 0.1 "
"的值相加，也不會產生精準的 0.3："
#: ../../tutorial/floatingpoint.rst:122
"Also, since the 0.1 cannot get any closer to the exact value of 1/10 and 0.3 "
"cannot get any closer to the exact value of 3/10, then pre-rounding with :"
"func:`round` function cannot help:"
"同時，因為 0.1 不能再更接近精準的 1/10，還有 0.3 不能再更接近精準的 3/10，預"
"先用 :func:`round` 函式捨入並不會有幫助："
#: ../../tutorial/floatingpoint.rst:131
"Though the numbers cannot be made closer to their intended exact values, "
"the :func:`math.isclose` function can be useful for comparing inexact values:"
"雖然數字不會再更接近他們的精準數值，但 :func:`math.isclose` 函式可以用來比較"
#: ../../tutorial/floatingpoint.rst:139
"Alternatively, the :func:`round` function can be used to compare rough "
"approximations::"
msgstr "或者，可以使用 :func:`round` 函式來比較粗略的近似值： ::"
#: ../../tutorial/floatingpoint.rst:147
"Binary floating-point arithmetic holds many surprises like this.  The "
"problem with \"0.1\" is explained in precise detail below, in the "
"\"Representation Error\" section.  See `Examples of Floating Point Problems "
"<https://jvns.ca/blog/2023/01/13/examples-of-floating-point-problems/>`_ for "
"a pleasant summary of how binary floating-point works and the kinds of "
"problems commonly encountered in practice.  Also see `The Perils of Floating "
"Point <https://www.lahey.com/float.htm>`_ for a more complete account of "
"other common surprises."
"二進位浮點數架構下還有很多這樣的意外。底下的「表示法誤差 (Representation "
"Error)」章節，詳細地解釋了「0.1」的問題。`Examples of Floating Point Problems"
"（浮點數問題範例） <https://jvns.ca/blog/2023/01/13/examples-of-floating-"
"point-problems/>`_\\ 一文提供了二進位浮點數的作用方式與現實中這類常見問題的摘"
"錄。如果想要其他常見問題的更完整描述，可以參考 `The Perils of Floating Point"
"（浮點數的風險） <https://www.lahey.com/float.htm>`_。"
#: ../../tutorial/floatingpoint.rst:156
"As that says near the end, \"there are no easy answers.\"  Still, don't be "
"unduly wary of floating-point!  The errors in Python float operations are "
"inherited from the floating-point hardware, and on most machines are on the "
"order of no more than 1 part in 2\\*\\*53 per operation.  That's more than "
"adequate for most tasks, but you do need to keep in mind that it's not "
"decimal arithmetic and that every float operation can suffer a new rounding "
"如同上文的末段所述，「這個問題並沒有簡單的答案。」不過，也不必對浮點過度擔"
"心！Python 的 float（浮點數）運算中的誤差，是從浮點硬體繼承而來，而在大多數的"
"計算機上，每次運算的誤差範圍不會大於 2\\*\\*53 分之 1。這對大多數的任務來說已"
"經相當足夠，但你需要記住，它並非十進位運算，且每一次 float 運算都可能會承受新"
#: ../../tutorial/floatingpoint.rst:163
"While pathological cases do exist, for most casual use of floating-point "
"arithmetic you'll see the result you expect in the end if you simply round "
"the display of your final results to the number of decimal digits you "
"expect. :func:`str` usually suffices, and for finer control see the :meth:"
"`str.format` method's format specifiers in :ref:`formatstrings`."
"雖然浮點運算確實存在一些問題，但在一般情況下，如果你只是把最終結果的顯示值，"
"以十進位方式捨入至預期的位數，那麼仍會得到你預期的結果。:func:`str` 通常就能"
"滿足要求，而若想要更細緻的控制，可參閱\\ :ref:`formatstrings`\\ 中關於 :meth:"
"`str.format` method（方法）的格式規範。"
#: ../../tutorial/floatingpoint.rst:169
"For use cases which require exact decimal representation, try using the :mod:"
"`decimal` module which implements decimal arithmetic suitable for accounting "
"applications and high-precision applications."
"對於需要精準十進位表示法的用例，可以試著用 :mod:`decimal` 模組，它可實作適用"
"於會計應用程式與高精確度應用程式的十進位運算。"
#: ../../tutorial/floatingpoint.rst:173
"Another form of exact arithmetic is supported by the :mod:`fractions` module "
"which implements arithmetic based on rational numbers (so the numbers like "
"1/3 can be represented exactly)."
"另一種支援精準運算的格式為 :mod:`fractions` 模組，該模組基於有理數來實作運算"
"（因此可以精確表示像 1/3 這樣的數字）。"
#: ../../tutorial/floatingpoint.rst:177
"If you are a heavy user of floating-point operations you should take a look "
"at the NumPy package and many other packages for mathematical and "
"statistical operations supplied by the SciPy project. See <https://scipy."
"如果你是浮點運算的重度使用者，你應該看一下 NumPy 套件，以及由 SciPy 專案提供"
"的許多用於數學和統計學運算的其他套件。請參閱 <https://scipy.org>。"
#: ../../tutorial/floatingpoint.rst:181
"Python provides tools that may help on those rare occasions when you really "
"*do* want to know the exact value of a float.  The :meth:`float."
"as_integer_ratio` method expresses the value of a float as a fraction:"
"在罕見情況下，當你\\ *真的*\\ 想知道一個 float 的精準值，Python 提供的工具可"
"協助達成。:meth:`float.as_integer_ratio` method 可將一個 float 的值表示為分"
#: ../../tutorial/floatingpoint.rst:192
"Since the ratio is exact, it can be used to losslessly recreate the original "
msgstr "由於該比率是精準的，它可無損地再現該原始值："
#: ../../tutorial/floatingpoint.rst:200
"The :meth:`float.hex` method expresses a float in hexadecimal (base 16), "
"again giving the exact value stored by your computer:"
":meth:`float.hex` method 以十六進位（基數為 16）表示 float，一樣可以給出你的"
"電腦所儲存的精準值："
#: ../../tutorial/floatingpoint.rst:208
"This precise hexadecimal representation can be used to reconstruct the float "
"value exactly:"
msgstr "這種精確的十六進位表示法可用於精準地重建 float 值："
#: ../../tutorial/floatingpoint.rst:216
"Since the representation is exact, it is useful for reliably porting values "
"across different versions of Python (platform independence) and exchanging "
"data with other languages that support the same format (such as Java and "
"由於該表示法是精準的，因此適用於在不同版本的 Python 之間可靠地傳送數值（獨立"
"於系統平台），並與支援相同格式的其他語言（如 JAVA 和 C99）交換資料。"
#: ../../tutorial/floatingpoint.rst:220
"Another helpful tool is the :func:`sum` function which helps mitigate loss-"
"of-precision during summation.  It uses extended precision for intermediate "
"rounding steps as values are added onto a running total. That can make a "
"difference in overall accuracy so that the errors do not accumulate to the "
"point where they affect the final total:"
"另一個有用的工具是 :func:`sum` 函式，能在計算總和時幫忙減少精確度的損失。當數"
"值被加到運行中的總計值時，它會追蹤「失去的位數 (lost digits)」。這可以明顯改"
"善總體準確度 (overall accuracy)，使得誤差不至於累積到影響最終總計值的程度："
#: ../../tutorial/floatingpoint.rst:233
"The :func:`math.fsum()` goes further and tracks all of the \"lost digits\" "
"as values are added onto a running total so that the result has only a "
"single rounding.  This is slower than :func:`sum` but will be more accurate "
"in uncommon cases where large magnitude inputs mostly cancel each other out "
"leaving a final sum near zero:"
":func:`math.fsum()` 更進一步將數值被加到運行總計中的總計時追蹤所有「失去的位"
"數」，以便結果僅有一次捨入。這比 :func:`sum` 慢，但在不常見的情況下會更準確，"
"在這種情況下，大量輸入大多相互抵消，最終的總和會接近於零："
#: ../../tutorial/floatingpoint.rst:260
msgid "Representation Error"
msgstr "表示法誤差 (Representation Error)"
#: ../../tutorial/floatingpoint.rst:262
"This section explains the \"0.1\" example in detail, and shows how you can "
"perform an exact analysis of cases like this yourself.  Basic familiarity "
"with binary floating-point representation is assumed."
"本節將會詳細解釋「0.1」的例子，並說明你自己要如何對類似案例執行精準的分析。 "
"以下假設你對二進位浮點表示法已有基本程度的熟悉。"
#: ../../tutorial/floatingpoint.rst:266
":dfn:`Representation error` refers to the fact that some (most, actually) "
"decimal fractions cannot be represented exactly as binary (base 2) "
"fractions. This is the chief reason why Python (or Perl, C, C++, Java, "
"Fortran, and many others) often won't display the exact decimal number you "
":dfn:`Representation error`\\ （表示法誤差）是指在真實情況中，有些（實際上是"
"大多數）十進位小數並不能精準地以二進位（基數為 2）小數表示。這是 Python（或 "
"Perl、C、C++、JAVA、Fortran 和其他許多）通常不會顯示你期望的精準十進位數字的"
#: ../../tutorial/floatingpoint.rst:271
"Why is that?  1/10 is not exactly representable as a binary fraction.  Since "
"at least 2000, almost all machines use IEEE 754 binary floating-point "
"arithmetic, and almost all platforms map Python floats to IEEE 754 binary64 "
"\"double precision\" values.  IEEE 754 binary64 values contain 53 bits of "
"precision, so on input the computer strives to convert 0.1 to the closest "
"fraction it can of the form *J*/2**\\ *N* where *J* is an integer containing "
"exactly 53 bits. Rewriting ::"
"為什麼呢？因為 1/10 無法精準地以一個二進位小數來表示。至少自從 2000 年以來，"
"幾乎所有的計算機皆使用 IEEE-754 浮點數運算標準，並且幾乎所有的平台都以 IEEE "
"754 binary64 標準中的「雙精度 (double precision)」來作為 Python 的 float。"
"IEEE 754 binary64 的值包含 53 位元的精度，所以在輸入時，電腦會努力把 0.1 轉換"
"到最接近的分數，以 *J*/2**\\ *N* 的形式表示，此處 *J* 是一個正好包含 53 位元"
"的整數。可以將：\n"
#: ../../tutorial/floatingpoint.rst:282
msgid "as ::"
#: ../../tutorial/floatingpoint.rst:286
"and recalling that *J* has exactly 53 bits (is ``>= 2**52`` but ``< "
"2**53``), the best value for *N* is 56:"
"而前面提到 *J* 有精準的 53 位元（即 ``>= 2**52`` 但 ``< 2**53``），所以 *N* "
"的最佳數值是 56："
#: ../../tutorial/floatingpoint.rst:294
"That is, 56 is the only value for *N* that leaves *J* with exactly 53 bits.  "
"The best possible value for *J* is then that quotient rounded:"
"意即，要使 *J* 正好有 53 位元，則 56 會是 *N* 的唯一值。而 *J* 最有可能的數值"
"就是經過捨入後的該商數："
#: ../../tutorial/floatingpoint.rst:303
"Since the remainder is more than half of 10, the best approximation is "
"obtained by rounding up:"
msgstr "由於餘數超過 10 的一半，所以最佳的近似值是透過進位而得："
#: ../../tutorial/floatingpoint.rst:313
"Therefore the best possible approximation to 1/10 in IEEE 754 double "
"precision is::"
"所以，在 IEEE 754 雙精度下，1/10 的最佳近似值是：\n"
#: ../../tutorial/floatingpoint.rst:318
"Dividing both the numerator and denominator by two reduces the fraction to::"
"將分子和分母同除以二，會約分為：\n"
#: ../../tutorial/floatingpoint.rst:322
"Note that since we rounded up, this is actually a little bit larger than "
"1/10; if we had not rounded up, the quotient would have been a little bit "
"smaller than 1/10.  But in no case can it be *exactly* 1/10!"
"請注意，由於我們有進位，所以這實際上比 1/10 大了一點；如果我們沒有進位，商數"
"將會有點小於 1/10。但在任何情況下都不可能是\\ *精準的* 1/10！"
#: ../../tutorial/floatingpoint.rst:326
"So the computer never \"sees\" 1/10:  what it sees is the exact fraction "
"given above, the best IEEE 754 double approximation it can get:"
"所以電腦從來沒有「看到」1/10：它看到的是上述的精準分數，也就是它能得到的 "
"IEEE 754 double 最佳近似值：\n"
#: ../../tutorial/floatingpoint.rst:334
"If we multiply that fraction by 10\\*\\*55, we can see the value out to 55 "
"decimal digits:"
msgstr "如果將該分數乘以 10\\*\\*55，則可以看到該值以 55 個十進位數字顯示："
#: ../../tutorial/floatingpoint.rst:342
"meaning that the exact number stored in the computer is equal to the decimal "
"value 0.1000000000000000055511151231257827021181583404541015625. Instead of "
"displaying the full decimal value, many languages (including older versions "
"of Python), round the result to 17 significant digits:"
"這表示儲存在電腦中的精準數值等於十進位值 "
"位數值，許多語言（包括 Python 的舊版本）選擇將結果捨入至 17 個有效位數："
#: ../../tutorial/floatingpoint.rst:352
"The :mod:`fractions` and :mod:`decimal` modules make these calculations easy:"
msgstr ":mod:`fractions` 與 :mod:`decimal` 模組能使這些計算變得容易："
Sunbelt Computer Software

PL/B Language Development and Support

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Uh oh!

Sunbelt Computer Software

PL/B Language Development and Support

Uh oh!

FilesExpand file tree

floatingpoint.po

Latest commit

History

floatingpoint.po

File metadata and controls
