Hi Julian,
Thanks for facilitating the communication, I probably should have
dropped you
from the reply as it was intended for the list in general as well as the
PR submitter.
Thanks, Roger
On 3/4/22 2:08 AM, Julian Waters wrote:
Hi all,
I apologize for the confusion, it seems like something went awry on my end
with the mailing lists, since there are apparently now 2 copies of the same
thread with different names. I guess I'll just go with this one, since the
technical discussion is going on here.
To clarify, I wasn't the one who created the PR, I'll relay the feedback to
the author since I'm not really in the position to give any feedback
myself, given my inexperience with this area of the JDK.
Thank you Stuart and Roger for the replies, have a great day! :)
best regards,
Julian
On Fri, Mar 4, 2022 at 1:37 PM Stuart Marks <stuart.ma...@oracle.com> wrote:
I agree with Roger. Let me amplify this.
The general rule for collections that use hashes and comparison methods
(such as
HashMap and TreeMap, as well as PriorityQueue) is that one mustn't mutate
any
element that resides in such a collection in any way that changes the
results of
hashCode, equals, or the comparison method. It's a bad precedent to add
APIs that
seem to support such mutation. As Roger said, the supported way of doing
this is to
remove, mutate, and then reinsert.
It seems like it might be safe to mutate an element, only temporarily
violating the
PQ's invariants until the mutated element is sifted into the correct
position.
However, even a "temporary" violation is exceedingly dangerous. If some
other
modification is made to the PQ while it's in this state, it could end up
permanently
corrupting the PQ.
Managing such a situation would need to be handled exceedingly carefully.
As such,
this seems like a highly specialized use case, thus the proposal isn't
suitable as a
general-purpose API.
s'marks
On 3/3/22 10:18 AM, Roger Riggs wrote:
Hi Julian,
Modifying the priorities of elements in the PriorityQueue violates the
invariants of the PriorityQueue established at insertion and maintained
at removal by the Comparator.
To maintain the invariant the element should be removed, its priority
modified,
and re-inserted.
An API to manually manipulate the order is inconsistent with the design
of
PriorityQueue.
Regards, Roger
On 3/3/22 6:59 AM, Jules W. wrote:
Hi all,
A new PR that adds methods to PriorityQueue was created some time ago at
https://github.com/openjdk/jdk/pull/6938 but has no corresponding
issue. As
I'm not too familiar with this part of the JDK I'm querying this mailing
list for anyone to properly review the PR before I create an issue for
it
in the JBS
best regards,
Julian Waters
