Re: math.erfc OverflowError
On 13 Jun 2010 18:23:28 -0700 a...@pythoncraft.com (Aahz) wrote: What's your cite that URLs never end with a period? AFAIK, that's perfectly valid by the rules. Technically that may be true but when do you ever see one? If your email client discards trailing periods I think you can expect it to do the right thing virtually 100% of the time. -- D'Arcy J.M. Cain da...@druid.net | Democracy is three wolves http://www.druid.net/darcy/| and a sheep voting on +1 416 425 1212 (DoD#0082)(eNTP) | what's for dinner. -- http://mail.python.org/mailman/listinfo/python-list
Re: math.erfc OverflowError
On Sun, Jun 13, 2010 at 10:36 PM, Ben Finney ben+pyt...@benfinney.id.au wrote: geremy condra debat...@gmail.com writes: You know, I've never been a part of a community in which the URL format was the most contentious part of filing a bug report. Heck no, the bug report is already filed, and contentions about the bug report should presumably be going into that report. This issue isn't about the bug report at all. The contentious issue here is how to *refer to* a bug report by URL in a plain-text natural-language medium :-) -- \ “How wonderful that we have met with a paradox. Now we have | `\ some hope of making progress.” —Niels Bohr | _o__) | Ben Finney I love this quote, and have added it to my list of potential future tattoos. Geremy Condra -- http://mail.python.org/mailman/listinfo/python-list
Re: math.erfc OverflowError
In article mailman.1348.1276386991.32709.python-l...@python.org, geremy condra debat...@gmail.com wrote: Bug filed, http://bugs.python.org/issue8986. Please don't put extraneous punctuation on URLs. That period is a valid URL character, but it's invalid for this URL, and it's not obvious to the reader whether the period should be part of the URL. URLs in general should go on their own line, but at least separate them with whitespace (or use the icky angle-bracket hack supported by most mail/newsreaders). -- Aahz (a...@pythoncraft.com) * http://www.pythoncraft.com/ If you don't know what your program is supposed to do, you'd better not start writing it. --Dijkstra -- http://mail.python.org/mailman/listinfo/python-list
Re: math.erfc OverflowError
On Jun 13, 12:56 am, geremy condra debat...@gmail.com wrote: On Sat, Jun 12, 2010 at 4:40 PM, Robert Kern robert.k...@gmail.com wrote: On 2010-06-12 17:49 , geremy condra wrote: In Python3.2, calling math.erfc with a value in [-27.2, -30) raises an OverflowError: math range error. This is inconsistent with the erfc function from scipy (scipy.special.erfc) as well as with the C99 function by the same name, both of which return 2. I suspect that this is the result of the cutoff for the use of the continuing fraction approximation of erfc beginning when abs(x) 30, but I'm not sure. Is this desired behavior or should I file a bug report? Bug, I think. Bug filed,http://bugs.python.org/issue8986. A bug indeed. Many thanks for catching and reporting this, Geremy; it would have been embarrassing for Python 2.7 to be released with this bug in it. (Well, I would have been embarrassed, anyway; not sure about anyone else.) In case anyone cares, the bug was due to a misinterpreted errno value: there's an exp(-x*x) term in the formulas for erf(x) and erfc(x), and that term underflows to zero at abs(x) = sqrt(1075*log(2)), which is around 27.297. Some system math libraries (unfortunately not including the ones I tested on; I *did* test, honest!) set errno on underflow to zero; this errno value was then being misinterpreted as an indication of overflow by Python's general libm wrappings. Anyway, it's fixed now. -- Mark -- http://mail.python.org/mailman/listinfo/python-list
Re: math.erfc OverflowError
On 13 Jun 2010 09:49:03 -0700 a...@pythoncraft.com (Aahz) wrote: Bug filed, http://bugs.python.org/issue8986. Please don't put extraneous punctuation on URLs. That period is a valid URL character, but it's invalid for this URL, and it's not obvious to the reader whether the period should be part of the URL. URLs in general should go on their own line, but at least separate them with whitespace (or use the icky angle-bracket hack supported by most mail/newsreaders). Or get a proper mail/news reader. That URL is perfectly fine. Any reader that can't figure out that URLs never end with a period should be chucked. This ain't the seventies where people had to format their input exactly as the computer demanded. -- D'Arcy J.M. Cain da...@druid.net | Democracy is three wolves http://www.druid.net/darcy/| and a sheep voting on +1 416 425 1212 (DoD#0082)(eNTP) | what's for dinner. -- http://mail.python.org/mailman/listinfo/python-list
Re: math.erfc OverflowError
In article mailman.1409.1276477866.32709.python-l...@python.org, D'Arcy J.M. Cain da...@druid.net wrote: On 13 Jun 2010 09:49:03 -0700 a...@pythoncraft.com (Aahz) wrote: Please don't put extraneous punctuation on URLs. That period is a valid URL character, but it's invalid for this URL, and it's not obvious to the reader whether the period should be part of the URL. URLs in general should go on their own line, but at least separate them with whitespace (or use the icky angle-bracket hack supported by most mail/newsreaders). Or get a proper mail/news reader. That URL is perfectly fine. Any reader that can't figure out that URLs never end with a period should be chucked. This ain't the seventies where people had to format their input exactly as the computer demanded. What's your cite that URLs never end with a period? AFAIK, that's perfectly valid by the rules. -- Aahz (a...@pythoncraft.com) * http://www.pythoncraft.com/ If you don't know what your program is supposed to do, you'd better not start writing it. --Dijkstra -- http://mail.python.org/mailman/listinfo/python-list
Re: math.erfc OverflowError
a...@pythoncraft.com (Aahz) writes: In article mailman.1348.1276386991.32709.python-l...@python.org, geremy condra debat...@gmail.com wrote: Bug filed, http://bugs.python.org/issue8986. Please don't put extraneous punctuation on URLs. The punctuation isn't extraneous; it's a necessary part of a natural English sentence. That's where it belongs. Better is to follow the “Recommendations for Delimiting URI in Context” in RFC 2396 URL:http://www.ietf.org/rfc/rfc2396.txt, which allow natural punctuation around such delimited URLs. -- \ “I find the whole business of religion profoundly interesting. | `\ But it does mystify me that otherwise intelligent people take | _o__)it seriously.” —Douglas Adams | Ben Finney -- http://mail.python.org/mailman/listinfo/python-list
Re: math.erfc OverflowError
On Sun, Jun 13, 2010 at 6:44 PM, Ben Finney ben+pyt...@benfinney.id.au wrote: a...@pythoncraft.com (Aahz) writes: In article mailman.1348.1276386991.32709.python-l...@python.org, geremy condra debat...@gmail.com wrote: Bug filed, http://bugs.python.org/issue8986. Please don't put extraneous punctuation on URLs. The punctuation isn't extraneous; it's a necessary part of a natural English sentence. That's where it belongs. Better is to follow the “Recommendations for Delimiting URI in Context” in RFC 2396 URL:http://www.ietf.org/rfc/rfc2396.txt, which allow natural punctuation around such delimited URLs. You know, I've never been a part of a community in which the URL format was the most contentious part of filing a bug report. Geremy Condra -- http://mail.python.org/mailman/listinfo/python-list
Re: math.erfc OverflowError
On Sun, 13 Jun 2010 19:05:28 -0700, geremy condra wrote: On Sun, Jun 13, 2010 at 6:44 PM, Ben Finney ben+pyt...@benfinney.id.au wrote: a...@pythoncraft.com (Aahz) writes: In article mailman.1348.1276386991.32709.python-l...@python.org, geremy condra debat...@gmail.com wrote: Bug filed, http://bugs.python.org/issue8986. [...] You know, I've never been a part of a community in which the URL format was the most contentious part of filing a bug report. Good lord man, don't you realise what you've done??? In your reply to Mark on the tracker, you misused a hyphen as an m-dash, and to add insult to injury you then got the spacing around it completely wrong. We have to stamp this behaviour out before it spreads. It's already affected Mark, who replied and used three(!) hyphens instead of an m- dash. This is completely unacceptable!!! -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: math.erfc OverflowError
geremy condra debat...@gmail.com writes: You know, I've never been a part of a community in which the URL format was the most contentious part of filing a bug report. Heck no, the bug report is already filed, and contentions about the bug report should presumably be going into that report. This issue isn't about the bug report at all. The contentious issue here is how to *refer to* a bug report by URL in a plain-text natural-language medium :-) -- \ “How wonderful that we have met with a paradox. Now we have | `\some hope of making progress.” —Niels Bohr | _o__) | Ben Finney -- http://mail.python.org/mailman/listinfo/python-list
Re: math.erfc OverflowError
On 2010-06-12 17:49 , geremy condra wrote: In Python3.2, calling math.erfc with a value in [-27.2, -30) raises an OverflowError: math range error. This is inconsistent with the erfc function from scipy (scipy.special.erfc) as well as with the C99 function by the same name, both of which return 2. I suspect that this is the result of the cutoff for the use of the continuing fraction approximation of erfc beginning when abs(x) 30, but I'm not sure. Is this desired behavior or should I file a bug report? Bug, I think. -- Robert Kern I have come to believe that the whole world is an enigma, a harmless enigma that is made terrible by our own mad attempt to interpret it as though it had an underlying truth. -- Umberto Eco -- http://mail.python.org/mailman/listinfo/python-list
Re: math.erfc OverflowError
On Sat, Jun 12, 2010 at 4:40 PM, Robert Kern robert.k...@gmail.com wrote: On 2010-06-12 17:49 , geremy condra wrote: In Python3.2, calling math.erfc with a value in [-27.2, -30) raises an OverflowError: math range error. This is inconsistent with the erfc function from scipy (scipy.special.erfc) as well as with the C99 function by the same name, both of which return 2. I suspect that this is the result of the cutoff for the use of the continuing fraction approximation of erfc beginning when abs(x) 30, but I'm not sure. Is this desired behavior or should I file a bug report? Bug, I think. -- Robert Kern Bug filed, http://bugs.python.org/issue8986. Geremy Condra -- http://mail.python.org/mailman/listinfo/python-list
Re: math.erfc OverflowError
On Sat, 12 Jun 2010 15:49:37 -0700, geremy condra wrote: In Python3.2, calling math.erfc with a value in [-27.2, -30) raises an OverflowError: math range error. This is inconsistent with the erfc function from scipy (scipy.special.erfc) as well as with the C99 function by the same name, both of which return 2. I suspect that this is the result of the cutoff for the use of the continuing fraction approximation of erfc beginning when abs(x) 30, but I'm not sure. Is this desired behavior or should I file a bug report? Geremy, I know that as a general rule, whenever a person finds what seems to be a bug in Python (or the standard library) they should suspect their own mistake rather than a bug, but I think this is taking caution to extremes. The domain of erfc is the set of all real numbers, and the result is bounded by [0, 2]. So asking if OverflowError is desired behaviour is a bit like the fellow who bought a new car and then asked if it's supposed to catch fire when starting the engine... :) -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: math.erfc OverflowError
On Sat, Jun 12, 2010 at 11:05 PM, Steven D'Aprano st...@remove-this-cybersource.com.au wrote: On Sat, 12 Jun 2010 15:49:37 -0700, geremy condra wrote: In Python3.2, calling math.erfc with a value in [-27.2, -30) raises an OverflowError: math range error. This is inconsistent with the erfc function from scipy (scipy.special.erfc) as well as with the C99 function by the same name, both of which return 2. I suspect that this is the result of the cutoff for the use of the continuing fraction approximation of erfc beginning when abs(x) 30, but I'm not sure. Is this desired behavior or should I file a bug report? Geremy, I know that as a general rule, whenever a person finds what seems to be a bug in Python (or the standard library) they should suspect their own mistake rather than a bug, but I think this is taking caution to extremes. The domain of erfc is the set of all real numbers, and the result is bounded by [0, 2]. So asking if OverflowError is desired behaviour is a bit like the fellow who bought a new car and then asked if it's supposed to catch fire when starting the engine... :) Well, that was more or less my feeling on it, but as a general rule my opinion on math in python doesn't seem to be shared, so I thought I'd ask. Geremy Condra -- http://mail.python.org/mailman/listinfo/python-list
