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From Gilles <>
Subject Re: [MATH] Interest in large patches for small cleanup / performance changes?
Date Sat, 09 Nov 2013 22:21:44 GMT
On Sat, 09 Nov 2013 13:13:05 -0800, Phil Steitz wrote:
> On 11/5/13 5:21 AM, Gilles wrote:
>>>>> [...]
>>>>> I have scanned for exact duplicates quite a few times and never
>>>>> found any.  There are quite a few that are similar, but differ in
>>>>> material ways (strict versus non-strict inequalities, endpoints
>>>>> included / not included, etc.).  Please do not "collapse" 
>>>>> messages
>>>>> at the expense of loss of specificity or correctness.
>>> Look at the messages.  These are different.  They convey different
>>> information and are appropriate in different contexts.  See below.
>> I've argued that context information should be constructed at the
>> point where the exception is thrown (where the context is known).
>> Not all combinations of exceptions and context need be present in
>> the pattern list.
>> This is the essence of my proposal below.
>>>> My position: the error (failed bracketing) should have its own
>>>> exception
>>>> type. The varying contexts could (do not have to) be part of the
>>>> message
>>>> built at exception instantiation.
>>>> If we want to include an indication of location (despite it is
>>>> already
>>>> part of the stack trace, so it is _redundant_), we could perhaps
>>>> add methods
>>>> to the "ExceptionContext", e.g. "where(LocalizeFormats pattern)"
>>>> (?).
>>>> Then, we would have thos patterns in the list:
>>>> Note: INVALID and FAILED are redundant since the pattern is
>>>> intended to be
>>>> included in an exception.
>>>> A second "interesting" case is
>>>> which mixes documentation with error description. Does anyone
>>>> really thinks
>>>> that the enumeration of the rounding methods in the error message
>>>> is necessary
>>>> or even helpful?
>>> When I throw an exception, I want to provide an error message that
>>> is meaningful in the context of the caller, i.e., that someone
>>> looking at a log or stack trace can make sense of.  That sometimes
>>> means restating preconditions, sometimes pointing to boundary
>>> conditions, sometimes giving hints describing common causes of the
>>> exception - lots of different things that depend on the API, the
>>> activation context and the nature of the exception.  The natural 
>>> way
>>> to do this is to use natural language sentences.  Please allow me 
>>> to
>>> retain a straightforward way to construct these messages and to
>>> maintain the specificity and meaning of the messages.
>> IMHO, the level of details in the message is not needed: if the
>> exception
>> was thrown, the user should probably look at the documentation,
>> rather
>> than try another value at random; I'd say that it is harmful to
>> tempt the
>> users with something like "Pick another number". ;-)
>> [Shouldn't we rather provide function where the rounding type is
>> an enum?]
>> The main problem in those discussions is that you consider only 
>> "toy"
>> situations, where the message generated by Commons Math should
>> make sense
>> wherever the exception is caught, and even if it is not caught.
> What you keep failing to acknowledge is that in many real world
> applications, reading exception stack traces and application logs
> that contain error messages is an important operational activity.
> Having clear error messages that make sense in the context of the
> stack trace or application activation context makes the job of those
> maintaining and debugging those applications easier.  However hard
> we decide to make it, I will continue to provide these.

IMO, the real problem is old habits, period. Despite your repeating it
over and over, I never expressed anything in the sense of having less
information in the error messages. [I don't get what the stack trace 
to do here. And I just gave you a real example where whatever details
CM tries to provide, it will _never_ be sufficient because it cannot
know why the call failed; I suggested that the _same_ amount of
(necessary but not sufficient) information could perhaps be provided
with "little block" patterns glued with "addMessage" (or an improvement
Specific exceptions always provide more information than less specific
ones. Keeping low-level message (e.g. precondition failure) does not
preclude adding more specific messages when the context is known (that
happens in the code, and every little variant does not need to be
hard-coded in the currently overly long list of patterns).
My proposals were solely aimed at making the "preparation" of the
messages more efficient from a developer's perspective (e.g. no 
of 300+ patterns).
Stalling the experiment in endless arguments makes it less and less
worth trying.

All in all, the main argument seems to always be that if the user
cannot see the difference, it is not worth changing the design.


> Phil
>> [I sometimes get a "failed bracketing" but knowing the values of 
>> "the
>> endpoints [that] have the same sign" does not really help. I'd
>> rather need
>> to catch the exception, add more context info, rethrow, recatch, 
>> etc.
>> And all this is quite more expensive than activating logging for
>> those
>> rare cases where numerical problems in the simulation trigger the
>> exception.]
>> Again and again, I do not mean that CM should not generate error
>> messages,
>> only that context info beyond a plain description of what happened 
>> is
>> rarely usable a few layers above the failed call. And that context
>> info
>> could be provided with much less than 300+ different messages.
>> Having little "building blocks" would also make it easier to 
>> retrieve
>> pattern/value pairs, as Luc seems willing to do, and more stable,
>> since
>> a single placeholder is unlikely to change meaning, while a
>> sentence that
>> contains many, could be turned differently so that the previous
>> placeholder
>> index could now refer to a different value.
>> Gilles
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