Stable priority queue

[Aaron W. LaFramboise]

Hello,

I understand that an easy way to make the standard std::priority_q ueue
stable is by including an integer stamp with each node that is
incremented each time a new node is pushed into the queue. However, no
matter what reasonably-sized type I use for the stamp, eventually the
stamp will 'wrap around' and possibly cause incorrect ordering of
elements. For my application, which queues elements very quickly and
runs for an indefinite amount of time, this scenario is a real concern,
and will eventually cause incorrect results.

Is there any easy and painless way of correcting this order-stamp
wraparound problem?
Aaron W. LaFramboise

[Howard]

"Aaron W. LaFramboise" <aa********@c ox-internet.com> wrote in message
news:10******** *****@corp.supe rnews.com...

Hello,

I understand that an easy way to make the standard std::priority_q ueue
stable is by including an integer stamp with each node that is
incremented each time a new node is pushed into the queue. However, no
matter what reasonably-sized type I use for the stamp, eventually the
stamp will 'wrap around' and possibly cause incorrect ordering of
elements. For my application, which queues elements very quickly and
runs for an indefinite amount of time, this scenario is a real concern,
and will eventually cause incorrect results.

Is there any easy and painless way of correcting this order-stamp
wraparound problem?
Aaron W. LaFramboise

I don't know if this will help you but...

In a server application I helped write, we got the local date/time info and
created a string from that which identified the ordering of the queue. We
set the string to be the following format:

YYYYMMDDHHNNSST TT

where

YYYY=year
MM=month
DD=day
HH=hours
NN=minutes
SS=seconds
TTT=millisecond s

(If you are queuing faster than that will allow for, then you can add an
integer count to the end of that, which can be free to wrap since you're not
likely to exceed THAT limit! :-))

That's worked fine for three years now. Wel, the system's been rebooted
several times in that time (it is Windows, after all :-)), but the queue is
restored on startup, so the ordering is still preserved properly.

-Howard

[Howard]

"Aaron W. LaFramboise" <aa********@c ox-internet.com> wrote in message
news:10******** *****@corp.supe rnews.com...

Hello,

I understand that an easy way to make the standard std::priority_q ueue
stable is by including an integer stamp with each node that is
incremented each time a new node is pushed into the queue. However, no
matter what reasonably-sized type I use for the stamp, eventually the
stamp will 'wrap around' and possibly cause incorrect ordering of
elements. For my application, which queues elements very quickly and
runs for an indefinite amount of time, this scenario is a real concern,
and will eventually cause incorrect results.

Is there any easy and painless way of correcting this order-stamp
wraparound problem?
Aaron W. LaFramboise

I don't know if this will help you but...

In a server application I helped write, we got the local date/time info and
created a string from that which identified the ordering of the queue. We
set the string to be the following format:

YYYYMMDDHHNNSST TT

where

YYYY=year
MM=month
DD=day
HH=hours
NN=minutes
SS=seconds
TTT=millisecond s

(If you are queuing faster than that will allow for, then you can add an
integer count to the end of that, which can be free to wrap since you're not
likely to exceed THAT limit! :-))

That's worked fine for three years now. Wel, the system's been rebooted
several times in that time (it is Windows, after all :-)), but the queue is
restored on startup, so the ordering is still preserved properly.

-Howard

[Siemel Naran]

"Aaron W. LaFramboise" <aa********@c ox-internet.com> wrote in message

I understand that an easy way to make the standard std::priority_q ueue
stable is by including an integer stamp with each node that is
incremented each time a new node is pushed into the queue. However, no
matter what reasonably-sized type I use for the stamp, eventually the
stamp will 'wrap around' and possibly cause incorrect ordering of
elements. For my application, which queues elements very quickly and
runs for an indefinite amount of time, this scenario is a real concern,
and will eventually cause incorrect results.

Is there any easy and painless way of correcting this order-stamp
wraparound problem?

What is a stable priority queue?

[Siemel Naran]

"Aaron W. LaFramboise" <aa********@c ox-internet.com> wrote in message

I understand that an easy way to make the standard std::priority_q ueue
stable is by including an integer stamp with each node that is
incremented each time a new node is pushed into the queue. However, no
matter what reasonably-sized type I use for the stamp, eventually the
stamp will 'wrap around' and possibly cause incorrect ordering of
elements. For my application, which queues elements very quickly and
runs for an indefinite amount of time, this scenario is a real concern,
and will eventually cause incorrect results.

Is there any easy and painless way of correcting this order-stamp
wraparound problem?

What is a stable priority queue?

[Kevin Goodsell]

Siemel Naran wrote:

What is a stable priority queue?

I'm guessing items of the same priority come out in the order they were
inserted.

-Kevin
--
My email address is valid, but changes periodically.
To contact me please use the address from a recent posting.

[Kevin Goodsell]

Siemel Naran wrote:

What is a stable priority queue?

I'm guessing items of the same priority come out in the order they were
inserted.

-Kevin
--
My email address is valid, but changes periodically.
To contact me please use the address from a recent posting.

[Jack Klein]

On Mon, 05 Apr 2004 14:57:53 -0500, "Aaron W. LaFramboise"
<aa********@c ox-internet.com> wrote in comp.lang.c++:

Hello,

I understand that an easy way to make the standard std::priority_q ueue
stable is by including an integer stamp with each node that is
incremented each time a new node is pushed into the queue. However, no
matter what reasonably-sized type I use for the stamp, eventually the
stamp will 'wrap around' and possibly cause incorrect ordering of
elements. For my application, which queues elements very quickly and
runs for an indefinite amount of time, this scenario is a real concern,
and will eventually cause incorrect results.

Is there any easy and painless way of correcting this order-stamp
wraparound problem?
Aaron W. LaFramboise

Define the time stamp as an unsigned long (or unsigned long long, if
your compiler supports this extension from C), and do the increment
like this:

if (timestamp < ULONG_MAX) /* ULLONG_MAX */
++timestamp;

Don't forget to include <limits.h> or <climits>.

If you are really likely to exceed 0xffffffff, the minimum possible
value for ULONG_MAX, and your implementation doesn't support 64 bit
integer types (long long or __int64), you could always use a double or
long double.

--
Jack Klein
Home: http://JK-Technology.Com
FAQs for
comp.lang.c http://www.eskimo.com/~scs/C-faq/top.html
comp.lang.c++ http://www.parashift.com/c++-faq-lite/
alt.comp.lang.l earn.c-c++
http://www.contrib.andrew.cmu.edu/~a...FAQ-acllc.html

[Jack Klein]

On Mon, 05 Apr 2004 14:57:53 -0500, "Aaron W. LaFramboise"
<aa********@c ox-internet.com> wrote in comp.lang.c++:

Hello,

I understand that an easy way to make the standard std::priority_q ueue
stable is by including an integer stamp with each node that is
incremented each time a new node is pushed into the queue. However, no
matter what reasonably-sized type I use for the stamp, eventually the
stamp will 'wrap around' and possibly cause incorrect ordering of
elements. For my application, which queues elements very quickly and
runs for an indefinite amount of time, this scenario is a real concern,
and will eventually cause incorrect results.

Is there any easy and painless way of correcting this order-stamp
wraparound problem?
Aaron W. LaFramboise

Define the time stamp as an unsigned long (or unsigned long long, if
your compiler supports this extension from C), and do the increment
like this:

if (timestamp < ULONG_MAX) /* ULLONG_MAX */
++timestamp;

Don't forget to include <limits.h> or <climits>.

If you are really likely to exceed 0xffffffff, the minimum possible
value for ULONG_MAX, and your implementation doesn't support 64 bit
integer types (long long or __int64), you could always use a double or
long double.

--
Jack Klein
Home: http://JK-Technology.Com
FAQs for
comp.lang.c http://www.eskimo.com/~scs/C-faq/top.html
comp.lang.c++ http://www.parashift.com/c++-faq-lite/
alt.comp.lang.l earn.c-c++
http://www.contrib.andrew.cmu.edu/~a...FAQ-acllc.html

[Siemel Naran]

"Kevin Goodsell" <us************ *********@never box.com> wrote in message

Siemel Naran wrote:

What is a stable priority queue?

I'm guessing items of the same priority come out in the order they were
inserted.

Then maybe we can use the protected member 'c'. The standard says

template <class T, class Container = std::vector<T>, ...>
class priority_queue {
protected:
Container c;
...
};

So we could derive our own class from priority_queue, and add read and write
functions that read directly into and out of 'c'. If deriving from a
non-polymorphic class bothers us, we can use private inheritance with using
declarations.

We could get stable queue's and stacks too.

Anyway, what is a priority_queue? Is it just like a queue, except that
items with the highest priority get retrieved by top() and pop() first? How
do they achieve O(lg(N)) for both push and pop (ie. how does the heap
work?).