on.
Any pointers appreciated, to more-or-less anything.
Regards,
Nick Maclaren.
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| application? Academia, Business, ...?
Mainly academic research, but that still covers many fields.
However, I am not and never have been a 'pure' academic, and
am as interested in other uses as in academic research.
Regards,
Nick Maclaren.
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becomes LESS likely the longer the server stays up
(i.e. the settling down problem).
No problem is as hard to find as one where you are firmly convinced that
it is somewhere other than where it is.
Regards,
Nick Maclaren.
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routine logging, or even has
options to log relevant events.
The first means that the strategy of restarting doesn't help. All
three mean that current logs are almost never any use.
Regards,
Nick Maclaren.
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to
| afford the glitch in availability.
Consider the marked phrase in the context of a Poisson process failure
model, and laugh. If you don't understand why I say that, I suggest
finding out the properties of the Poisson process!
Regards,
Nick Maclaren.
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is no solution.
I suggest that you do invest in a little learning and look up Poisson
processes.
| Keep your eye on the goal and your more likely to score!
And, if you have your eye on the wrong goal, you would generally be
better off not scoring :-)
Regards,
Nick Maclaren.
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(POSIX, Microsoft
etc.) Python will shield you from some problems, but not all.
There is precious little that you can do, because the root cause is
that the standards and specifications are hopelessly flawed.
Regards,
Nick Maclaren.
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threading memory model, to name one of the better documented
aspects. A Web search should provide you with more information on
the ghastly mess than any sane person wants to know.
And that is only one of many aspects :-(
Regards,
Nick Maclaren.
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me by Email, and can describe technically
what you are doing and (most importantly) what you are assuming, I
may be able to give some hints. But no promises.
Regards,
Nick Maclaren.
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,
you can't tell if threading has anything to do with the failure - given
what we know, it seems likely, but what Aahz says is how to tackle the
problem WHATEVER the cause.
Regards,
Nick Maclaren.
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-posting when you are responding to Email
is as discourteous as top-posting when you are responding to newsgroups.
| So I concede the point, and I'm bottom-posting like a good citizen. =20
Excellent!
Regards,
Nick Maclaren.
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known
for ages and are still legion. The reason that this is unlikely is
that it is both easy to spot and trivial to fix.
Regards,
Nick Maclaren.
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a
me, too or equivalent, and not responding in detail.
But you have been told both of those before.
Regards,
Nick Maclaren.
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it. But that is not very helpful. Specially if you are
| mucking about in C, as your title suggests...
Thanks. As someone else posted, the answer is PyDict_SetItemString
immediately after PyType_Ready.
Regards,
Nick Maclaren.
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. But that is the situation :-(
Regards,
Nick Maclaren.
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), but might reduce the number of problems.
Regards,
Nick Maclaren.
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such things very badly, and it is often possible
to create a file even if it exists and O_CREAT|O_EXCL is set. A similar
remark applies to 'special' files, even on fairly mainstream, local
filing systems.
Regards,
Nick Maclaren.
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instance creation is guaranteed to cause confusion, if nothing else.
Regards,
Nick Maclaren.
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easily provide
the latter.
Is there any documentation on the coercion function (nb_coerce)? It
seems to have unusual properties.
Thanks for any hints.
Regards,
Nick Maclaren.
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of cases, they give reasonable estimates of the error.
In others, they give a false sense of security :-(
Regards,
Nick Maclaren.
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Hmm. The extensions documentation describes how to add instance
members to a class (PyMemberDef), but I want to add a class member.
Yes, this is constant for all instances of the class.
Any pointers?
Regards,
Nick Maclaren.
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that you do.
| For people just getting into it, it can be shocking to realize just how
| wide the interval can become after some computations.
Yes. Even when you can prove (mathematically) that the bounds are
actually quite tight :-)
Regards,
Nick Maclaren.
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, despite them
having good backgrounds in mathematics, don't feel inferior!
Regards,
Nick Maclaren.
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numerical
problems to a FEW applications. Hence people will have to convert to
the much more expensive 128-bit decimal format for such work.
Bloatware rules. All your bits are belong to us.
Regards,
Nick Maclaren.
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rules.
Regards,
Nick Maclaren.
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to persuade people that their solution is better.
If they admitted the difficulties of using decimal floating-point, and
merely said but, overall, we think it is a better solution, I would
disagree but say nothing.
Regards,
Nick Maclaren.
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-
point number would give a different answer; this is needed to make
certain operations reliable.
The default formatting does the obvious thing :-)
Er, that's about it
Regards,
Nick Maclaren.
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, of which such powers may be one level.
This is better regarded as an optimisation of a common case than a true
data type. Now, there MAY be such a language that supports such things
as a proper data type, but I don't know of one.
Regards,
Nick Maclaren.
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in hardware. And the decimal formats are
significantly more complicated.
What I don't know is how much precision this approximation loses when
used in real applications, and I have never found anyone else who has
much of a clue, either.
Regards,
Nick Maclaren.
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MORE if they are going to support multiplication.
Coming back to the start, is fixing that little lot up REALLY easier
than encapsulating scaled integers to give a proper fixed-point type?
I think that you will find that it is much harder!
Regards,
Nick Maclaren.
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floating-point isn't MUCH worse than binary, from a numerical
point of view :-)
[*] Assuming signed magnitude, calculate the answer truncated towards
zero but keep track of whether it is exact. If not, force the last
bit to 1. An old, cheap approximation to rounding.
Regards,
Nick Maclaren
(as does Python PVM),
| so perhaps someone has already done so.
Yes. No problem.
| Also, what about various grid toolkits?
If you can find one that is robust enough for real work by someone who
is not deeply into developing Grid software, I will be amazed.
Regards,
Nick Maclaren.
--
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In article [EMAIL PROTECTED],
Carsten Haese [EMAIL PROTECTED] writes:
| On Thu, 2007-01-11 at 23:47 +, Nick Maclaren wrote:
| In article [EMAIL PROTECTED],
| Facundo Batista [EMAIL PROTECTED] writes:
| | Noud Aldenhoven wrote:
| |
| | When I was programming in a mathematical project I
.
That is dubious, but let's not start that one again.
Regards,
Nick Maclaren.
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are probably too mathematical to be used
in
|
| For the sake of me being less ignorant, could you please point me a
| language where irrational numbers are exact?
Some of the algebraic languages. (2/3)^(1/5) is held as such and
manipulated appropriately.
Yes, I know that's cheating :-)
Regards,
Nick
the problem in as much detail as you want, but would
very much rather not.
Regards,
Nick Maclaren.
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any base above
2 is significantly worse than base 2.
Regards,
Nick Maclaren.
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). It leaves all language aspects (including allowed
code movement) to C.
There are no concepts in common between C's and POSIX's consistency
specifications (even when they are precise enough to use), and so no
way of mapping the two standards together.
Regards,
Nick Maclaren.
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.
Regards,
Nick Maclaren.
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an apparently lightweight one (data sharing)
are both subtle and complicated.
Regards,
Nick Maclaren.
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a rational with small numerator and denominator, then
they are very likely to return it. I implemented fixed slash once, and
it is very easy to do - all it needs is a GCD routine - like rational,
it would be straightforward to add to Python as an extension type.
Regards,
Nick Maclaren.
--
http
:
if c == a :
break
a = c
That works in binary, but in no base above 2 (assuming that I haven't
made a stupid error writing it down). In THAT case, it is easy to fix
for decimal, but there are ways that it can show up that can be quite
tricky to fix.
Regards,
Nick Maclaren
memory, but that's how it is.
Regards,
Nick Maclaren.
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to.
The ASCI bunch favour Co-array Fortran, and its model matches Python
like a steam turbine is a match for a heart transplant.
[*] They are worth looking up, if you don't know about them.
Regards,
Nick Maclaren.
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it to the
programmer. It is therefore easy to put the processes on different
CPUs, and get the memory consistency right.
Regards,
Nick Maclaren.
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.
That is why many POSIX threads programs work until the genuinely
shared memory accesses become frequent enough that you get some to the
same location in a single machine cycle.
Regards,
Nick Maclaren.
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, and was and am fairly well
in touch with what is going on in HPC world-wide.
Regards,
Nick Maclaren.
--
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a course on computer arithmetic, and am just
now writing one on Python numerics, and confused people may contact
me - though I don't guarantee to help.
Regards,
Nick Maclaren.
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in the days before binary became standard,
and will clearly return with decimal.
Regards,
Nick Maclaren.
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()
of
| its elements.
Precisely. And it also applies to strings, which I had failed to
notice:
print (1,2)
('1', '2')
print 1, 2
1 2
Regards,
Nick Maclaren.
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x = (1.234567890125, 1.2345678901255)
print x
print x[0], x[1]
(1.234567890124, 1.2345678901254999)
1.23456789012 1.23456789013
Is there a rational reason, or is that simply an artifact of the way
that the code has evolved? It is clearly not a bug :-)
Regards,
Nick Maclaren.
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has evolved!
Regards,
Nick Maclaren.
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In article [EMAIL PROTECTED],
Bjoern Schliessmann [EMAIL PROTECTED] writes:
| Nick Maclaren wrote:
|
| Ah! That explains it. I would call that reason intermediate
| between rational and an artifact of the way the code has evolved!
|
| Which code has evolved? Those precision problems
In article [EMAIL PROTECTED], Fredrik Lundh [EMAIL PROTECTED] writes:
| Nick Maclaren wrote:
|
| The use of different precisions for the two cases is not, however,
| and it is that I was and am referring to.
|
| that's by design, of course. maybe you should look repr up
naive users.
Regards,
Nick Maclaren.
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of digits
after the decimal point for at least 60 years, probably 100; in 40 years
of IT and using dozens of programming languages, I have never seen
display used for that purpose.
Regards,
Nick Maclaren.
--
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if the current behaviour was changed. See
| http://www.python.org/sf/1534769
| for details.
Well, I wasn't complaining - merely querying.
If this approach is taken, it would be better to document it, so that
authors of derived classes follow the convention.
Regards,
Nick Maclaren.
--
http
of computing
and mathematics.
But, given that meaning, I now understand your point.
Regards,
Nick Maclaren.
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In article [EMAIL PROTECTED],
Hendrik van Rooyen [EMAIL PROTECTED] writes:
| Nick Maclaren [EMAIL PROTECTED] wrote:
|
| Not at all. I didn't say that they came in pairs. Consider:
|
| [str1, str2, agent1, str3, agent2, agent3, agent4, str4, ...]
|
| See Algol 68 for an example
out. That
is more than just odd - it is almost unbelievable. They are a very
basic data structure, after all!
Regards,
Nick Maclaren,
University of Cambridge Computing Service,
New Museums Site, Pembroke Street, Cambridge CB2 3QH, England.
Email: [EMAIL PROTECTED]
Tel.: +44 1223 334761Fax
of this.
Regards,
Nick Maclaren.
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In article [EMAIL PROTECTED],
greg [EMAIL PROTECTED] writes:
| Nick Maclaren wrote:
|
| Unfortunately, you are confusing the issue, because there are far
| more extraneous aspects than relevant ones, and your view of the
| similarities requires looking at the issue in a very strange way.
| I
sequences,
or whether they claim that wanting such a feature is heresy :-)
Regards,
Nick Maclaren.
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write code that abuses a
language construct in a way that is discouraged but just happens to
work, a couple of decades down the line it will stop working, because
someone will change the feature. Been there - been caught by that :-(
Regards,
Nick Maclaren.
--
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more extraneous aspects than relevant ones, and your view of the
similarities requires looking at the issue in a very strange way.
I think that I can see what you mean, but only just.
Regards,
Nick Maclaren.
--
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. But that
| doesn't mean the concept isn't real.
Of course the concept is real, but the point is that Python doesn't
embody the concept of homogeneity in lists, formally or informally,
as far as I know or anyone has pointed out.
Regards,
Nick Maclaren.
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also be possible to improve lists to make insertion an
O(log N) operation, not an O(N) one as at present, at the expense of
increasing the cost of indexing. Not necessarily as much as from the
present O(1) to O(log N), but still significantly. Python has chosen
not to do that.
Regards,
Nick
sense that I have located. As I posted earlier, if
anyone knows of one, please tell me.
Regards,
Nick Maclaren.
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, but should almost always come with
the rider Follow these unless you have good reasons to ignore them,
but do make sure that you understand the rules first before deciding
your rules are good. Some of the responses here went a little, er,
a lot beyond that.
Regards,
Nick Maclaren.
--
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can't find
any that are as transparent to the user as I would really like.
There is method in my madness :-)
Regards,
Nick Maclaren.
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In article [EMAIL PROTECTED],
Michele Simionato [EMAIL PROTECTED] writes:
| Nick Maclaren wrote:
| It would be much cleaner not to have to fiddle with static
| members after the class is initialised.
|
| You can hide the fiddling, for instance with the trick explained here:
|
| http
Why doesn't the tuple type have an index method? It seems such a
bizarre restriction that there must be some reason for it. Yes,
I know it's a fairly rare requirement.
Regards,
Nick Maclaren.
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restriction!
Eh? Why?
My understanding of the difference between a tuple and a list is
PRECISELY that the former is immutable and the latter mutable.
But an index method makes precisely as much sense on an immutable
sequence as it does on a mutable one.
Regards,
Nick Maclaren.
--
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am now
confused by is the reason for the explanations
Regards,
Nick Maclaren.
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at
all clear, is not defined for Python tuples. There is no technical or
mathematical reason why it shouldn't be.
Regards,
Nick Maclaren.
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In article [EMAIL PROTECTED],
Fredrik Lundh [EMAIL PROTECTED] writes:
| Nick Maclaren wrote:
|
| If lists are intended to be homogeneous, then they should be checked
| for that, and an exception raised when an attempt is to make them
| non-homogeneous.
|
| so how would that check work, given
and for all...
|
| http://www.python.org/search/hypermail/python-1992/0285.html
Wonderful! Thanks. Yes, that does. It makes perfect sense. I did
say that I thought it would be a rarely used feature :-)
Regards,
Nick Maclaren.
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that it has not been done because
Guido and others felt that it wasn't worth doing, but not that it is
hard to do.
Regards,
Nick Maclaren.
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a respectable tuple even in Guido's sense, being fixed
in number and value and just happening to be homogeneous). ]
Regards,
Nick Maclaren.
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to be a serious piece of
misdesign, but there isn't a huge amount of point unless it is done
properly. Unreliable safety devices are as likely to increase
errors as reduce them, at least in the hands of the naive.
Regards,
Nick Maclaren.
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be used until after the class has been created properly. Actually,
it won't be used except to test for class equivalence, but I may
want to extend later.
Regards,
Nick Maclaren.
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already doing that, and regretting the fact that Python
doesn't seem to allow a class instantiation to return a new class :-)
What I am trying to do is very simple, but is somewhat unusual. That
is the story of my life, so I am used to having problems.
Regards,
Nick Maclaren.
--
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; there are specific physical problems
where they are fundamental. I have never used them, in 40 years of
wide-ranging experience in the scientific computing arena!
Regards,
Nick Maclaren.
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reasons that
'program proving' has never taken off outside its cabal is that it
uses bizarre notations unlike anything else on earth that can't be
edited in a normal fashion.
Regards,
Nick Maclaren.
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INVENT that convention, you
know.
The bug isn't in passing an information string stdin but in using
that string (which is not meant to represent a real file) to perform a
file search.
Regards,
Nick Maclaren.
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.
Regards,
Nick Maclaren.
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on or largely cloned from
Unix. You should look at the POSIX facilities, but don't rely on
them without checking.
Also think very carefully whether you want to separate by user or
job - the latter is trickier under Unix.
Regards,
Nick Maclaren.
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file permissions (on Linux, at least).
They aren't on most Unices - Linux is not UNIX, you know :-)
I shall not respond further on this.
Regards,
Nick Maclaren.
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there for a while.
Create a file called 'stdin' in your current directory containing
'print Oh, yeah?\n' and then import a module that doesn't exist.
Don't include the single quotes.
Regards,
Nick Maclaren.
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In article [EMAIL PROTECTED],
Simon Forman [EMAIL PROTECTED] writes:
| Nick Maclaren wrote:
| ...
| Create a file called 'stdin' in your current directory containing
| 'print Oh, yeah?\n' and then import a module that doesn't exist.
| Don't include the single quotes.
|
| Why would you have
the bug is.
| I don't know whether this is worth fixing.
It's definitely worth fixing, but not as a high priority. Invoking a
file spuriously is potentially serious, with very low probability.
Regards,
Nick Maclaren.
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In article [EMAIL PROTECTED],
Fredrik Lundh [EMAIL PROTECTED] writes:
| Nick Maclaren wrote:
|
| It's definitely worth fixing, but not as a high priority. Invoking a
| file spuriously is potentially serious, with very low probability.
|
| the traceback printer is reading the file (using
The way that I read it, Python allows only values (and hence types)
to be immutable, and not class members. The nearest approach to the
latter is to use the name hiding conventions.
Is that correct?
Regards,
Nick Maclaren.
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In article [EMAIL PROTECTED],
Robert Kern [EMAIL PROTECTED] writes:
| Nick Maclaren wrote:
| The way that I read it, Python allows only values (and hence types)
| to be immutable, and not class members. The nearest approach to the
| latter is to use the name hiding conventions
that needs to
be in the reference manual, but is only in whatsnew2.2.
Regards,
Nick Maclaren.
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to be
| lacking.
Consider it considered, but I have to start by understanding what is
supposed to happen and what does happen, precisely and in detail.
Regards,
Nick Maclaren.
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Traceback (most recent call last):
File crap.py, line 14, in module
a.joe()
TypeError: 'NoneType' object is not callable
VERY weird - I could understand it if I got the error and DIDN'T succeed
in the call
Regards,
Nick Maclaren.
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. That certainly doesn't appear to be the case, and I don't
see how it helps with my original request if not.
Regards,
Nick Maclaren.
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extract its meaning from its
words.
Regards,
Nick Maclaren.
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directly.
But no matter - it is clear I had completely misunderstood the intent.
Regards,
Nick Maclaren.
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