Re: [Playerstage-users] confused about AddReplaceRule()

[Brian G. <br...@ge...>]

hi Jack,

It looks to me like what you're doing should in fact work.  I would  
start debugging in MessageQueue::CheckReplace(), in libplayercore/ 
message.cc.  That's where the queue decides whether to replace a  
particular message.  I'd specifically look at the way it iterates  
through the stored MessageReplaceRules, calling  
MessageReplaceRule::Match() on each.

	brian.

On Mar 19, 2007, at 4:43 PM, Jack O'Quin wrote:

> I'm working on the player driver for a local navigation and
> obstacle avoidance in a car.
>
> This driver subscribes to several devices:
>
>  * a position2d for controlling the vehicle
>  * another position2d that reports odometry
>  * a laser interface
>  * an opaque occupancy grid interface
>
> There are two clients sending it "order" commands using
> a different opaque interface.  One gives it waypoints
> to follow with a set of behavior hints.  The other is
> a diagnostic monitor, which may asynchronously
> tell the navigator to pause or resume its run.
>
> I need most of these interfaces set to "pull with replace"
> so the navigator always uses the latest sensor data
> when making decisions.
>
> That works fine, just setting replace mode in the
> constructor and requesting pull mode for the queue
> like this...
>
> // constructor, requesting overwrite of commands
> NavQueueMgr::NavQueueMgr(ConfigFile* cf, int section)
>     : Driver(cf, section, true, PLAYER_MSGQUEUE_DEFAULT_MAXLEN,
>              PLAYER_OPAQUE_CODE)
> {
>   InQueue->SetPull(true);
>
> BUT, I need to allow queuing of the commands giving orders
> to control the navigator's state.  Otherwise, a pause command
> may be lost due the the nearly simultaneous arrival of a
> waypoint following command.
>
> What I would like to do is set replace mode to false for these
> commands only, leaving everything else alone.  Then I can implement
> a priority scheme for the requested behaviors, with run and pause
> having higher priority than waypoint following.  I tried to do that
> by adding the following call immediately after the code above...
>
>   // allow queuing of opaque Order messages, but nothing else
>   int my_index = 0;			// TODO: parse "provides" to get this
>   InQueue->AddReplaceRule(-1, -1, PLAYER_OPAQUE_CODE, my_index,
> 			  PLAYER_MSGTYPE_CMD, PLAYER_OPAQUE_CMD, false);
>
> This has no discernable effect.  I experimented with setting the
> index to -1 instead of 0, but that did not work either.  Setting
> replace mode globally to false seems to result in handling all the
> order messages, but it looks like I only see one at a time, never
> two in the same ProcessMessages() cycle, so I fear I am getting
> behind in processing commands (as well as sensor inputs).
>
> Clearly, I do not understand how the queue management works.
> A few hints would be greatly appreciated (code to look at, etc.).
> I looked at the libplayercore/message.cc implementation, but it
> appears to do about what I expected, which is not what I see.
>
> Maybe this is all just a silly misunderstanding of the docs.
> -- 
>  joq
>
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