Accelerating ROS simulation to faster than real time

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Hi,

It's hard to believe, but according to my research I am the only one who would like to accelerate simulation of a ROS robot... and it seems to be an almost impossible task.

It looks like when I create a node that generates faster than real time clock topic, it totally messes up the simulation. Not even bags can be replayed faster, than real time.

The reason, as I found is that a huge part of the ROS system relies on WallTime and WallDurations, and not just by using these classes, but by doing waits and sleeps in wall times relevant in the simulation.

I tried to create an accelerated version of ROS:

• Removed the definitions of WallTime and SteadyTime, replaced them with typedefs to Time
• Removed the definition of WallDuration and replaced it with typedef to Duration
• Scaled all timed waits with my desired acceleration factor
• Instead of a clock topic I share the time from a timer process in shared memory, so all calls to Time::now() are in sync

But now I get stuck in various timing issues related to transformations, more specifically I get errors, like:

Lookup would require extrapolation into the future.  Requested time 1270387817.717999935 but the latest data is at time 1270387817.482000113

(Note that the timestamp is intentionally in the past, as it is an accelerated time, not the real time.)

Now in the stack trace, as I see, this is happening in waitForTransform() call, which is called with Time(0) by the simulation (stdr_simulator). And this is weird, semantically, as I would think (by the name of it) that waitForTransform() is intended to wait, until the transform is available, not throw an exception that it is not (yet).

Could please someone help here?

UPDATE I think the problem is somehow related to BufferCore::getLatestCommonTime(). Somehow the cached times does not match the cached transforms.