[jira] [Commented] (MATH-742) Please make PolynomialSplineFunction Serializable
[
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]
Neil Roeth commented on MATH-742:
-
Of course, I'm fine moving the general discussion elsewhere. IIRC, that
suggestion was made earlier in this thread by someone. :-) To answer your
specific questions:
bq. I don't understand why the idiom would break down with the addition of a
private field; the only requirement is that a class provides accessors to
everything one needs to reconstruct an identical object.
I meant private fields with no public accessors, and the requirement you state
is precisely the one that would make the class impossible to serialize with the
idiom while it would be possible with the other methods.
bq. Could you give a concrete example where one would need to serialize a RNG
(where it must continue drawing from the same sequence)?
Pretty much any RNG should continue using the same sequence rather than
restarting from a new seed if the sequences are meant to model the same random
element. So, a calculation where you do part of the calculation, do some
processing, then do some calculation might be an example. However, evaluating
whether this particular case needs to be serialized is missing the point. The
point is that there are classes (like this RNG) where the constructor
preconditions that the idiom depends upon are nowhere near sufficient to
guarantee that an identical object can be created. If you prefer, think of
class A with a constructor that takes an argument of class B, then creates from
that an internal instance of class C that is required to completely define the
state of an instance of A. There is no public accessor for C because that
field has no meaning outside of the class itself. The instance of class B used
to construct the instance of A is useless after the object is constructed, so
it is not saved and therefore is not available at serialization/deserialization
time to construct a new instance. The idiom cannot handle that, but the default
serialization or explicit writeObject() and readObject() methods can (as long
as class C is made Serializable).
I would be happy to respond to the other, more general points, but since you
asked to suspend further comments on the general issue and others are probably
tired of the discussion :-), I'll not do so.
Please make PolynomialSplineFunction Serializable
-
Key: MATH-742
URL: https://issues.apache.org/jira/browse/MATH-742
Project: Commons Math
Issue Type: Improvement
Affects Versions: 2.2
Reporter: Neil Roeth
Priority: Minor
Attachments: PolynomialSplineFunction.java
PolynomialSplineFunction is not Serializable, while the very similar
PolynomialFunction class in the same package is. All that needs to be done is
to add the import:
{{import java.io.Serializable;}}
and change this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction}}
to this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction, Serializable}}
I made exactly that modification to a local copy and it serialized
successfully. Before the change, I got serialization errors.
Thanks.
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[jira] [Commented] (MATH-742) Please make PolynomialSplineFunction Serializable
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]
Gilles commented on MATH-742:
-
bq. I am not understanding what problems this could cause - can you give some
explicit examples? I don't know what your criteria are for appropriate
serialization code - can you describe a case where the default serialization
code is not appropriate and why it is not appropriate?
I guess that the most trivial problem is serializing with some version of the
library and deserializing with another where the internal structure has changed
in the meantime (e.g. substituting one instance variable with another that
would provide the same basic functionality).
Please note that the position which I am defending here is not based on my
criteria for how to handle Serializable. I'm reporting concerns very well
explained in the book Effective Java by J. Bloch. Those concerns might be
far-fetched and we are totally entitled to ignore them in standalone
applications but in the case of a _library_, we should not presume of the
innocuousness of anything we put in.
bq. As far as I can tell, the writeObject() and readObject() methods in
ExceptionContext are unnecessary because they simply do what the default
mechanism does anyway (except that it replaces throwing an exception for a
non-serializable object with a String that says it is non-serializable). What
am I missing?
That the exception context is part of the exceptions defined in CM: If a
non-Serializable object is stored in the context, it must be detected, lest
the default serialization generates another exception, the result of which
would be that the original exception cannot be propagated remotely.
Concerning your last series of points, there are answers at several different
levels.
* Policy (as a means toward consistency of code design, implementation and
maintenance): Cf. previous posts.
* Resources: CM's core business is mathematical utilities programmed in clear
OO Java code. This alone is already too much for a small team. Adding more
administrivia is IMHO unreasonable ATM.
* There is no encapsulation breaking: The code uses only public accessors in
order to extract the objectively meaningful data that are needed to define the
concept represented by PolynomialSplineFunction (the knots and the set of
coefficients of the polynomial functions that are connected at the knots).
* In some sense, the default serialization breaks the encapsulation because the
object is deserialized without undergoing the constructor's precondition
checks; while the SerializationProxy actually enforces encapsulation by
passing the deserialized to the constructor.
Please make PolynomialSplineFunction Serializable
-
Key: MATH-742
URL: https://issues.apache.org/jira/browse/MATH-742
Project: Commons Math
Issue Type: Improvement
Affects Versions: 2.2
Reporter: Neil Roeth
Priority: Minor
Attachments: PolynomialSplineFunction.java
PolynomialSplineFunction is not Serializable, while the very similar
PolynomialFunction class in the same package is. All that needs to be done is
to add the import:
{{import java.io.Serializable;}}
and change this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction}}
to this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction, Serializable}}
I made exactly that modification to a local copy and it serialized
successfully. Before the change, I got serialization errors.
Thanks.
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[jira] [Commented] (MATH-742) Please make PolynomialSplineFunction Serializable
[
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]
Luc Maisonobe commented on MATH-742:
bq. I guess that the most trivial problem is serializing with some version of
the library and deserializing with another where the internal structure has
changed in the meantime (e.g. substituting one instance variable with another
that would provide the same basic functionality).
I think we can simply say this is not supported. Serialization should not be
used for long time storage, and even if it can be used for distributed
computation with different versions between client and server, we can simply
say we don't support it.
bq. Those concerns might be far-fetched and we are totally entitled to ignore
them in standalone applications but in the case of a library, we should not
presume of the innocuousness of anything we put in.
+1 for the concerns of a library, but there are many cases when a simple
implements Serializable is sufficient and does not imply too much work.
Could we go for a case by case policy ? There are some classes where
serialization could help users and not be too cumbersome. This is a trade off
between forbidding serialization completely and supporting it for all classes
in a guaranteed way with cross-version support.
Please make PolynomialSplineFunction Serializable
-
Key: MATH-742
URL: https://issues.apache.org/jira/browse/MATH-742
Project: Commons Math
Issue Type: Improvement
Affects Versions: 2.2
Reporter: Neil Roeth
Priority: Minor
Attachments: PolynomialSplineFunction.java
PolynomialSplineFunction is not Serializable, while the very similar
PolynomialFunction class in the same package is. All that needs to be done is
to add the import:
{{import java.io.Serializable;}}
and change this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction}}
to this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction, Serializable}}
I made exactly that modification to a local copy and it serialized
successfully. Before the change, I got serialization errors.
Thanks.
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[jira] [Commented] (MATH-742) Please make PolynomialSplineFunction Serializable
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]
Neil Roeth commented on MATH-742:
-
Responding to Luc:
bq. I think we can simply say this is not supported. Serialization should not
be used for long time storage, and even if it can be used for distributed
computation with different versions between client and server, we can simply
say we don't support it.
Completely reasonable.
bq. +1 for the concerns of a library, but there are many cases when a simple
implements Serializable is sufficient and does not imply too much work.
Yes, agreed. I think this is one of them.
Responding to Gilles:
bq. There is no encapsulation breaking: The code uses only public accessors
in order to extract the objectively meaningful data that are needed to define
the concept represented by PolynomialSplineFunction (the knots and the set of
coefficients of the polynomial functions that are connected at the knots).
Well, yes, but add a private field critical to the state of PolynomialFunction
and the idiom breaks down. There would be no breakdown if the class itself
were responsible for ensuring that readObject() and writeObject() did the right
thing.
Here's an example: Suppose you have a random number generator class RngGilles
that has a constructor that takes a single long integer as an argument. The
constructor precondition returns true for any value of the long integer. With
that long integer, it initializes a private table of several hundred long
integers and a private marker of its current position in the table. When
RngGilles.nextRandom() is called, it calculates the value to be returned from
the table and its current place in the table , then updates the table and its
current place, then returns the value. It does this a billion times, then
needs to be serialized and deserialized in order to continue to use that same
random number sequence in another process. The idiom would fail in that case,
while the default writeObject() and readObject() would succeed.
bq. In some sense, the default serialization breaks the encapsulation because
the object is deserialized without undergoing the constructor's precondition
checks; while the SerializationProxy actually enforces encapsulation by
passing the deserialized to the constructor.
I understand what you are saying, but the concept of serialization is that when
you are done deserializing, you have an object that represents the exact same
state as the object that was serialized, so since it already satisfied any
constructor preconditions when it was first created, there is no need to check
them again. It is, of course, possible to subvert this for some particular
class, e.g., through poorly written explicit writeObject() and readObject()
methods, or by failing to mark some fields transient and making methods that
use the transient field handle that, but I'd call that a bug in that particular
object's serialization implementation, not a general failure of serialization
that needs to be handled outside the class by serialization wrappers. ISTM
that the idiom basically boils down to deconstructing objects to their
primitive fields and then reconstructing them from those primitives, completely
bypassing the whole Serialization mechanism except for those primitive fields.
Please make PolynomialSplineFunction Serializable
-
Key: MATH-742
URL: https://issues.apache.org/jira/browse/MATH-742
Project: Commons Math
Issue Type: Improvement
Affects Versions: 2.2
Reporter: Neil Roeth
Priority: Minor
Attachments: PolynomialSplineFunction.java
PolynomialSplineFunction is not Serializable, while the very similar
PolynomialFunction class in the same package is. All that needs to be done is
to add the import:
{{import java.io.Serializable;}}
and change this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction}}
to this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction, Serializable}}
I made exactly that modification to a local copy and it serialized
successfully. Before the change, I got serialization errors.
Thanks.
--
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[jira] [Commented] (MATH-742) Please make PolynomialSplineFunction Serializable
[
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]
Gilles commented on MATH-742:
-
According to the general convention, this discussion should be ported to the
dev ML, possibly with a subject prefix of [ALL] so that we can get opinions
of people who are much more knowledgeable than me on the pros and cons of
supporting serialization.
After I respond to the last points raised here, we could maybe suspend the
comments in this forum...
Adding an implements Serializable on a case-by-case basis is not a substitute
for a policy (i.e. defining what would be the ideal state for CM). Personally,
I think that it will not help users in the long-term, because they will know
(because we'll tell them) that they should not rely on a serialization policy
that reads {{Serializable}} is added for your convenience but is otherwise
unsupported.
I don't understand why the idiom would break down with the addition of a
private field; the only requirement is that a class provides accessors to
everything one needs to reconstruct an identical object.
Could you give a concrete example where one would need to serialize a RNG
(where it must continue drawing from the same sequence)?
There is one subversion which you did not mention (which is the one that
usually comes up when the experts talk about serialization) is the possible
corruption (accidental or intentional) that could happen while the data goes
over the wire. That's what the idiom can thwart.
On the other hand, you enumerate many sources of possible bugs in the
implementation of serialization: That's exactly why I say that _we_ should not
implement it, unless we have people on the team that can commit to support it!
But that would come back to the issue of policy, having a discussion on the
dev ML about what should be the serialized form, which classes should be
serializable and which not, how to decide for border-line cases, etc.
That's a moderately ambitious project. IMHO, it is people like you, that would
benefit from it, who should primarily contribute to it, even if just to start
the discussion on the ML to get on the right track.
As I told at the beginning, the issue is not simply to add implements
Serializable to PolynomialSplienFunction, even if the current lack of
consistency in CM would have you believed that it was, for which we apologize.
;-)
Please make PolynomialSplineFunction Serializable
-
Key: MATH-742
URL: https://issues.apache.org/jira/browse/MATH-742
Project: Commons Math
Issue Type: Improvement
Affects Versions: 2.2
Reporter: Neil Roeth
Priority: Minor
Attachments: PolynomialSplineFunction.java
PolynomialSplineFunction is not Serializable, while the very similar
PolynomialFunction class in the same package is. All that needs to be done is
to add the import:
{{import java.io.Serializable;}}
and change this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction}}
to this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction, Serializable}}
I made exactly that modification to a local copy and it serialized
successfully. Before the change, I got serialization errors.
Thanks.
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[jira] [Commented] (MATH-742) Please make PolynomialSplineFunction Serializable
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]
Neil Roeth commented on MATH-742:
-
First, thanks for continuing to respond, I do want to understand the reasoning
behind this decision and you are helping make it clear.
{quote}
We are already in trouble, because of this lack of policy, for several classes
for which Serializable is a supposedly innocuous feature (e.g. fields that
should be transient cannot be because no explicit serialization is implemented).
{quote}
Do you mean that if you corrected this and made them transient, you would
introduce an incompatibility with objects serialized using older versions of
the class? If not that, then could you explain?
{quote}
In the Commons project, there is a commitment that minor releases must be fully
compatible; that implies that relying on a default serialization would prevent
any change to internal structure of a class.
{quote}
I understand completely about not making changes in minor releases. Since that
commitment is for minor releases, that implies that it could be done at the
next major release, right?
{quote}
Maybe that you are not aware of the constraints imposed by Serializable;
maybe that you don't care because in your use-case, you'll never be confronted
to the problem of a wrong serialized form. But another user's use-case might
bring him here complaining about our inconsistent support of Serializable.
Would he be less right than you?
{quote}
Not aware is more likely than don't care. I may be ignorant but I'm not
callous. :-) I understand that suddenly changing how a class is serialized
could break things for use cases other than mine and that is no less right than
mine. Another reason to restrict the change to a major version.
{quote}
It is always trivial to add implements Serializable to a class definition.
But it is not trivial to do the implementation in the right way; just adding
implements Serializable is not the right way, never. Again, it could be good
enough for some purpose, but the wish for CM to be an example of good Java
programming, is not compatible with statements such as We know it's sloppy, so
don't use it whenever you need something that works
{quote}
This is the core of the issue. I can see that implementing Serializable might
require special code in some cases, but why is just adding implements
Serializable _never_ the right way? You provided an example of wrapper code to
do serialization for a class that is not serializable, but would you provide an
example of how to transform a class that is not serializable directly into one
that is? I.e., not with a wrapper, but by adding implements Serializable and
then adding the explicit serialization methods to the class itself? I would
like to see an example of good Java programming with regard to serialization.
{quote}
The purpose of CM is to provide robust implementations of mathematical
utilities; supporting distributed applications is a totally different game.
{quote}
In my business, we often do massive calculations that require hundreds or
thousands of cpu-hours that need to be completed overnight, so they need to be
distributed. Regardless of how robust the implementation is otherwise, if it
does not support distribution, then that alone might make it unusable.
Please make PolynomialSplineFunction Serializable
-
Key: MATH-742
URL: https://issues.apache.org/jira/browse/MATH-742
Project: Commons Math
Issue Type: Improvement
Affects Versions: 2.2
Reporter: Neil Roeth
Priority: Minor
Attachments: PolynomialSplineFunction.java
PolynomialSplineFunction is not Serializable, while the very similar
PolynomialFunction class in the same package is. All that needs to be done is
to add the import:
{{import java.io.Serializable;}}
and change this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction}}
to this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction, Serializable}}
I made exactly that modification to a local copy and it serialized
successfully. Before the change, I got serialization errors.
Thanks.
--
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[jira] [Commented] (MATH-742) Please make PolynomialSplineFunction Serializable
[
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]
Gilles commented on MATH-742:
-
bq. Do you mean that if you corrected this and made them transient, you would
introduce an incompatibility with objects serialized using older versions of
the class? If not that, then could you explain? [...]
It was an example of a case where the appropriate serialization code might be
missing. In other words, because it is so simple to add Serializable _just in
case_, we create problems for later.
My main point is that CM should not spend its scarce human resources to provide
features (in that case: support for serialization) that _should_ require
careful planning.
But if people want to contribute, they will bring the feature, together with
the necessary unit testing. Personally, I think that there should be a
commitment to *support* the feature...
However, as you've understood, my preference would really be to drop all
Serializable but the indispensable (I was convinced by the remotely-generated
exception use case).
This case will also give you the example of implementing the explicit
serialization methods (if that's what you asked): Have a look at the
ExceptionContext class (in package o.a.c.m.exception.util).
In CM, the trends is currently going towards having immutable classes. The
constructors' precondition checks guarantee the state of the object and people
who want that serialization provides the same guarantee (where good Java
programming includes robustness) have come up with the idiom which I've
adapted above for PolynomialSplineFunction.
Please make PolynomialSplineFunction Serializable
-
Key: MATH-742
URL: https://issues.apache.org/jira/browse/MATH-742
Project: Commons Math
Issue Type: Improvement
Affects Versions: 2.2
Reporter: Neil Roeth
Priority: Minor
Attachments: PolynomialSplineFunction.java
PolynomialSplineFunction is not Serializable, while the very similar
PolynomialFunction class in the same package is. All that needs to be done is
to add the import:
{{import java.io.Serializable;}}
and change this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction}}
to this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction, Serializable}}
I made exactly that modification to a local copy and it serialized
successfully. Before the change, I got serialization errors.
Thanks.
--
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[jira] [Commented] (MATH-742) Please make PolynomialSplineFunction Serializable
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]
Neil Roeth commented on MATH-742:
-
{quote}
It was an example of a case where the appropriate serialization code might be
missing. In other words, because it is so simple to add Serializable just in
case, we create problems for later.
{quote}
I am not understanding what problems this could cause - can you give some
explicit examples? I don't know what your criteria are for appropriate
serialization code - can you describe a case where the default serialization
code is not appropriate and _why_ it is not appropriate?
As far as I can tell, the writeObject() and readObject() methods in
ExceptionContext are unnecessary because they simply do what the default
mechanism does anyway (except that it replaces throwing an exception for a
non-serializable object with a String that says it is non-serializable). What
am I missing?
Your code for a class that serializes PolynomialSplineFunction pulls
coefficients[] out of the underlying PolynomialFunction class and serializes
them. Why do that instead of just using PolynomialFunction.writeObject()? Why
is it better programming practice to create separate serialization classes that
have deep knowledge of the class structure of each of its data members rather
than encapsulate the serialization in each of those classes? If
PolynomialFunction implements Serializable, then either
PolynomialFunction.writeObject() will do the right thing or it is a bug in
PolynomialFunction's implementation of writeObject() - a serializer for
PolynomialSplineFunction shouldn't have to take on the responsibility of
serializing the guts of PolynomialFunction. I don't see how breaking
encapsulation like this is an improvement over the default mechanism, which
doesn't break it.
Please make PolynomialSplineFunction Serializable
-
Key: MATH-742
URL: https://issues.apache.org/jira/browse/MATH-742
Project: Commons Math
Issue Type: Improvement
Affects Versions: 2.2
Reporter: Neil Roeth
Priority: Minor
Attachments: PolynomialSplineFunction.java
PolynomialSplineFunction is not Serializable, while the very similar
PolynomialFunction class in the same package is. All that needs to be done is
to add the import:
{{import java.io.Serializable;}}
and change this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction}}
to this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction, Serializable}}
I made exactly that modification to a local copy and it serialized
successfully. Before the change, I got serialization errors.
Thanks.
--
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[jira] [Commented] (MATH-742) Please make PolynomialSplineFunction Serializable
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]
Gilles commented on MATH-742:
-
bq. It is perfectly fine to make only part of the library Serializable.
And the policy must provide an clear decision-making procedure to select
between the part that will be Serializable and the one that won't.
We are already in trouble, because of this lack of policy, for several classes
for which Serializable is a supposedly innocuous feature (e.g. fields that
should be transient cannot be because no _explicit_ serialization is
implemented).
In the Commons project, there is a commitment that minor releases must be fully
compatible; that implies that relying on a default serialization would prevent
*any* change to internal structure of a class.
Maybe that you are not aware of the constraints imposed by Serializable;
maybe that you don't care because in your use-case, you'll never be confronted
to the problem of a wrong serialized form. But another user's use-case might
bring him here complaining about our inconsistent support of Serializable.
Would he be less right than you?
It is always trivial to add implements Serializable to a class definition.
But it is not trivial to do the implementation in the right way; just adding
implements Serializable is not the right way, never. Again, it could be good
enough for some purpose, but the wish for CM to be an example of good Java
programming, is not compatible with statements such as We know it's sloppy, so
don't use it whenever you need something that works
The purpose of CM is to provide robust implementations of mathematical
utilities; supporting distributed applications is a totally different game.
Easing the use of CM in distributed applications is a worthy enhancement, but
it should not put the primary goal at risk (like blocking development because
it would be tied by puny considerations of backwards compatibility not even
related to the core business).
Hence I think that it has to be thought about with more care than was done up
to now: You rightly pointed out the inconsistency of tagging
PolynomialFunction as serializable while PolynomialSplineFunction is not.
Personally, I'm really _not_ attached to backwards compatibility! So I wouldn't
mind making that class Serializable *until* we decide to clean up the mess.
Thus, if I have it my way, that would mean that in, say, version 4.0, *all* of
the CM classes (not obviously meant as data storage) will be stripped of their
trivial serializability.
Please make PolynomialSplineFunction Serializable
-
Key: MATH-742
URL: https://issues.apache.org/jira/browse/MATH-742
Project: Commons Math
Issue Type: Improvement
Affects Versions: 2.2
Reporter: Neil Roeth
Priority: Minor
Attachments: PolynomialSplineFunction.java
PolynomialSplineFunction is not Serializable, while the very similar
PolynomialFunction class in the same package is. All that needs to be done is
to add the import:
{{import java.io.Serializable;}}
and change this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction}}
to this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction, Serializable}}
I made exactly that modification to a local copy and it serialized
successfully. Before the change, I got serialization errors.
Thanks.
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[jira] [Commented] (MATH-742) Please make PolynomialSplineFunction Serializable
[
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]
Neil Roeth commented on MATH-742:
-
I'm kind of surprised at this result. One developer out of three objected, and
that's a consensus? That developer basically said this class should only be
Serialized if X, Y and Z were true. I responded that yes, indeed, it was
precisely X,Y and Z that were true and in fact were what led to my request.
I'd have thought that, all objections having been answered, it would have been
a done deal then. Particularly since PolynomialFunction, a class in the same
package, is already Serializable. Instead, Won't Fix? What objections were
raised that were not answered?
Luc, the work arounds you propose are poorer practice than using Serializable
exactly as it was intended. The work arounds both boil down to implement
serialization of PolynomialSplineFunction through home grown custom code
instead of simply adding the Java standard 'implements Serializable'. That is
not a better solution, so I am going to keep my locally customized version of
the class and hope you someday change your mind.
Please make PolynomialSplineFunction Serializable
-
Key: MATH-742
URL: https://issues.apache.org/jira/browse/MATH-742
Project: Commons Math
Issue Type: Improvement
Affects Versions: 2.2
Reporter: Neil Roeth
Priority: Minor
Attachments: PolynomialSplineFunction.java
PolynomialSplineFunction is not Serializable, while the very similar
PolynomialFunction class in the same package is. All that needs to be done is
to add the import:
{{import java.io.Serializable;}}
and change this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction}}
to this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction, Serializable}}
I made exactly that modification to a local copy and it serialized
successfully. Before the change, I got serialization errors.
Thanks.
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[jira] [Commented] (MATH-742) Please make PolynomialSplineFunction Serializable
[
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]
Gilles commented on MATH-742:
-
The following is what you need to serialize a {{PolynomialSplineFunction}}
object:
{code}
import java.io.Serializable;
import org.apache.commons.math3.analysis.polynomials.PolynomialSplineFunction;
import org.apache.commons.math3.analysis.polynomials.PolynomialFunction;
public class SerialPolynomialSpline extends PolynomialSplineFunction
implements Serializable {
public SerialPolynomialSpline(double[] knots,
PolynomialFunction[] coeff) {
super(knots, coeff);
}
private Object writeReplace() {
return new SerializationProxy(this);
}
private static class SerializationProxy
implements Serializable {
final double[] knots;
final double[][] coefficients;
public SerializationProxy() {
knots = null;
coefficients = null;
}
public SerializationProxy(SerialPolynomialSpline spline) {
knots = spline.getKnots();
final PolynomialFunction[] p = spline.getPolynomials();
coefficients = new double[p.length][];
for (int i = 0; i p.length; i++) {
coefficients[i] = p[i].getCoefficients();
}
}
Object readResolve() {
final PolynomialFunction[] p = new
PolynomialFunction[coefficients.length];
for (int i = 0; i p.length; i++) {
p[i] = new PolynomialFunction(coefficients[i]);
}
return new SerialPolynomialSpline(knots, p);
}
}
}
{code}
If you only need it for {{PolynomialSplineFunction}}, you'll write that once,
you'll test it (or not) and off you go.
In the case of a library, consistency is an important quality; thus, _we_ would
need to write that for all the classes, and test them all because by
implementing Serializable, we advertise that the class can be used robustly
in any application that would make use of that feature. We did not make that
promise, and one of the developers indeed pointed out that supporting
Serializable is not trivial in terms of maintenance.
As a matter fact, your issue raised the question of the CM policy with respect
to Serializable. I said that it could be that we implement Serializable for
everything, _in the right way_. Waiving that point as unrelated to your issue
was not very constructive. ;)
However, if you want to go in that direction, you are welcome to contribute.
Please make PolynomialSplineFunction Serializable
-
Key: MATH-742
URL: https://issues.apache.org/jira/browse/MATH-742
Project: Commons Math
Issue Type: Improvement
Affects Versions: 2.2
Reporter: Neil Roeth
Priority: Minor
Attachments: PolynomialSplineFunction.java
PolynomialSplineFunction is not Serializable, while the very similar
PolynomialFunction class in the same package is. All that needs to be done is
to add the import:
{{import java.io.Serializable;}}
and change this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction}}
to this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction, Serializable}}
I made exactly that modification to a local copy and it serialized
successfully. Before the change, I got serialization errors.
Thanks.
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[jira] [Commented] (MATH-742) Please make PolynomialSplineFunction Serializable
[
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]
Neil Roeth commented on MATH-742:
-
Gilles,
In many cases, the default serialization mechanism is perfectly adequate, as in
this case where no one, not even the library maintainers, actually needs to do
anything nearly as complex as this code you supplied. Is there any possible
problem that adding implements Serializable in this one class could cause?
The only possible problem you raised is that someone, somewhere, might possibly
save this class as long term storage. How about you make this one class
Serializable, and if you get a bug report that it doesn't work when someone
uses it for long term storage, you just tell that person Don't do that?
Meanwhile, the rest of us can go ahead and use the Serializable class properly,
in exactly the circumstances that you stated serialization was for, i.e.,
passing data around in distributed processing.
There is no reason to saddle my simple, isolated issue with the burden of
proving that the Commons Math team must commit to making the whole library
Serializable. It doesn't have to commit to that. It is perfectly fine to make
only part of the library Serializable. The last time I checked, only part of
the Java API was Serializable. Just add implements Serializable to this
class. Then, put a big, bold statement on the web page that says, We made
some parts of Commons Math Serializable where it was trivial to do so, but we
do not plan at this time to tackle the parts that are not trivial. Patches to
do the latter are welcome, as long as they do it IN THE RIGHT WAY. Then
declare success and be happy that you made the library more useful.
Please make PolynomialSplineFunction Serializable
-
Key: MATH-742
URL: https://issues.apache.org/jira/browse/MATH-742
Project: Commons Math
Issue Type: Improvement
Affects Versions: 2.2
Reporter: Neil Roeth
Priority: Minor
Attachments: PolynomialSplineFunction.java
PolynomialSplineFunction is not Serializable, while the very similar
PolynomialFunction class in the same package is. All that needs to be done is
to add the import:
{{import java.io.Serializable;}}
and change this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction}}
to this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction, Serializable}}
I made exactly that modification to a local copy and it serialized
successfully. Before the change, I got serialization errors.
Thanks.
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[jira] [Commented] (MATH-742) Please make PolynomialSplineFunction Serializable
[
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]
Leandro Ariel Pezzente commented on MATH-742:
-
Anyone has any thougths about this issue ?
Please make PolynomialSplineFunction Serializable
-
Key: MATH-742
URL: https://issues.apache.org/jira/browse/MATH-742
Project: Commons Math
Issue Type: Improvement
Affects Versions: 2.2
Reporter: Neil Roeth
Priority: Minor
PolynomialSplineFunction is not Serializable, while the very similar
PolynomialFunction class in the same package is. All that needs to be done is
to add the import:
{{import java.io.Serializable;}}
and change this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction}}
to this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction, Serializable}}
I made exactly that modification to a local copy and it serialized
successfully. Before the change, I got serialization errors.
Thanks.
--
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[jira] [Commented] (MATH-742) Please make PolynomialSplineFunction Serializable
[
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]
Luc Maisonobe commented on MATH-742:
Sounds good to me.
Note that once class becomes serializable, it should have a serialization ID.
We recently decided to use the date of the source file change as the idea in
short ISO-8601 format. So if the change were made today, the ID would be
20120210.
Please make PolynomialSplineFunction Serializable
-
Key: MATH-742
URL: https://issues.apache.org/jira/browse/MATH-742
Project: Commons Math
Issue Type: Improvement
Affects Versions: 2.2
Reporter: Neil Roeth
Priority: Minor
PolynomialSplineFunction is not Serializable, while the very similar
PolynomialFunction class in the same package is. All that needs to be done is
to add the import:
{{import java.io.Serializable;}}
and change this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction}}
to this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction, Serializable}}
I made exactly that modification to a local copy and it serialized
successfully. Before the change, I got serialization errors.
Thanks.
--
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[jira] [Commented] (MATH-742) Please make PolynomialSplineFunction Serializable
[
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]
Leandro Ariel Pezzente commented on MATH-742:
-
Ok. There , can you check if The changes have being made properly ?
Please make PolynomialSplineFunction Serializable
-
Key: MATH-742
URL: https://issues.apache.org/jira/browse/MATH-742
Project: Commons Math
Issue Type: Improvement
Affects Versions: 2.2
Reporter: Neil Roeth
Priority: Minor
Attachments: PolynomialSplineFunction.java
PolynomialSplineFunction is not Serializable, while the very similar
PolynomialFunction class in the same package is. All that needs to be done is
to add the import:
{{import java.io.Serializable;}}
and change this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction}}
to this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction, Serializable}}
I made exactly that modification to a local copy and it serialized
successfully. Before the change, I got serialization errors.
Thanks.
--
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[jira] [Commented] (MATH-742) Please make PolynomialSplineFunction Serializable
[
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]
Gilles commented on MATH-742:
-
In principle, I'm against applying the {{Serializable}} pseudo-interface.
In this case, as with most of what is in CM, we deal with an object whose main
purpose is to _compute_ something, not to store data. I know that the border
between data and computation is not clear-cut, especially in the OO paradigm...
But the main rationale is to not induce the users to think that it is good
practice to store data using the default serialization system. If I'm not
mistaken, this feature was meant to ease some of the plumbing needed for
distributed applications.
Serializable is certainly not to be taken as a substitute for a stable API
aimed at safe long-term storage. It is for this reason that I think that the
default should be to *not* implement Serializable unless there is a good
clear case (i.e. not one that displays a bad practice) that needs it. E.g.
there was the convincing case for the exception infrastructure (cf. package
exception.util) to be Serializable: Whenever some remote application using
CM needed to report a failure and could not unless the given exception could be
serialized.
Please make PolynomialSplineFunction Serializable
-
Key: MATH-742
URL: https://issues.apache.org/jira/browse/MATH-742
Project: Commons Math
Issue Type: Improvement
Affects Versions: 2.2
Reporter: Neil Roeth
Priority: Minor
Attachments: PolynomialSplineFunction.java
PolynomialSplineFunction is not Serializable, while the very similar
PolynomialFunction class in the same package is. All that needs to be done is
to add the import:
{{import java.io.Serializable;}}
and change this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction}}
to this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction, Serializable}}
I made exactly that modification to a local copy and it serialized
successfully. Before the change, I got serialization errors.
Thanks.
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[jira] [Commented] (MATH-742) Please make PolynomialSplineFunction Serializable
[
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]
Luc Maisonobe commented on MATH-742:
Instead of full file, we often prefer to get patches in the form of diff. It
simplifies checking the changes and applying them.
The problem with having non-serializable classes is that this completely
prevents them from being used as fields in user-defined classes which may need
to be serializable. Serialization is useful in many situations which are not
related to long-term storage and we should not prevent it. So as long as there
is no identified problem to have serializable classes (such as very big data
structures or singletons), then serializable could be added liberally.
Please make PolynomialSplineFunction Serializable
-
Key: MATH-742
URL: https://issues.apache.org/jira/browse/MATH-742
Project: Commons Math
Issue Type: Improvement
Affects Versions: 2.2
Reporter: Neil Roeth
Priority: Minor
Attachments: PolynomialSplineFunction.java
PolynomialSplineFunction is not Serializable, while the very similar
PolynomialFunction class in the same package is. All that needs to be done is
to add the import:
{{import java.io.Serializable;}}
and change this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction}}
to this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction, Serializable}}
I made exactly that modification to a local copy and it serialized
successfully. Before the change, I got serialization errors.
Thanks.
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[jira] [Commented] (MATH-742) Please make PolynomialSplineFunction Serializable
[
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]
Neil Roeth commented on MATH-742:
-
Luc, that is precisely my situation. I have a grid computing application where
my user-defined objects are returned from the grid, and they contain a
PolynomialSplineFunction that is a critical part of the calculated result.
Gilles, this is the plumbing needed for distributed applications in my case.
Please make PolynomialSplineFunction Serializable
-
Key: MATH-742
URL: https://issues.apache.org/jira/browse/MATH-742
Project: Commons Math
Issue Type: Improvement
Affects Versions: 2.2
Reporter: Neil Roeth
Priority: Minor
Attachments: PolynomialSplineFunction.java
PolynomialSplineFunction is not Serializable, while the very similar
PolynomialFunction class in the same package is. All that needs to be done is
to add the import:
{{import java.io.Serializable;}}
and change this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction}}
to this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction, Serializable}}
I made exactly that modification to a local copy and it serialized
successfully. Before the change, I got serialization errors.
Thanks.
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[
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]
Gilles commented on MATH-742:
-
bq. this completely prevents them from being used as fields in user-defined
classes which may need to be serializable
The issue (and my question) is: Is this field needed in the serialization? If
not, the user can add the transient keyword to the variable instance
declaration.
If it is needed, then again, is Serializable the correct way? That it is the
quick-and-dirty solution, I know.
Finally, if we don't care about advertising good (or bad) practice in this
area, then let's globally add Serializable to every class...
Is there a CheckStyle rule to detect such a requirement? Can anyone come up
with a script that would automatically do the job?
Please make PolynomialSplineFunction Serializable
-
Key: MATH-742
URL: https://issues.apache.org/jira/browse/MATH-742
Project: Commons Math
Issue Type: Improvement
Affects Versions: 2.2
Reporter: Neil Roeth
Priority: Minor
Attachments: PolynomialSplineFunction.java
PolynomialSplineFunction is not Serializable, while the very similar
PolynomialFunction class in the same package is. All that needs to be done is
to add the import:
{{import java.io.Serializable;}}
and change this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction}}
to this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction, Serializable}}
I made exactly that modification to a local copy and it serialized
successfully. Before the change, I got serialization errors.
Thanks.
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[
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]
Neil Roeth commented on MATH-742:
-
Gilles,
{quote}The issue (and my question) is: Is this field needed in the
serialization?{quote}
Yes.
{quote}If it is needed, then again, is Serializable the correct way?{quote}
As you said, [Serializable] was meant to ease some of the plumbing needed for
distributed applications, so since my application is distributed and needs
this plumbing, the answer is again yes.
I raised this issue to add Serializable to this one particular class; if you
want to discuss globally adding Serializable to every class, that's a different
issue. Could you please open a new issue to discuss that topic? Thanks.
Please make PolynomialSplineFunction Serializable
-
Key: MATH-742
URL: https://issues.apache.org/jira/browse/MATH-742
Project: Commons Math
Issue Type: Improvement
Affects Versions: 2.2
Reporter: Neil Roeth
Priority: Minor
Attachments: PolynomialSplineFunction.java
PolynomialSplineFunction is not Serializable, while the very similar
PolynomialFunction class in the same package is. All that needs to be done is
to add the import:
{{import java.io.Serializable;}}
and change this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction}}
to this:
{{public class PolynomialSplineFunction implements
DifferentiableUnivariateRealFunction, Serializable}}
I made exactly that modification to a local copy and it serialized
successfully. Before the change, I got serialization errors.
Thanks.
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