Set the maximum keyframes to avoid memory problems

[abylikhsanov]

Hi,

Is there a way to set a maximum number of keyframes or landmarks to set the maximum RAM size that is usable for SLAM? For example deleting old keyframes if certain threshold has exceeded and etc.

[ymd-stella]

No, it doesn't.
In addition, in the main branch, setting an upper limit on the number of keyframes does not reduce memory usage.

If high memory usage is your problem, I recommend you to use use-shared-ptr branch.
In this branch, unused keyframes are released.
The keyframe limit is not implemented yet, but if you create an issue for a feature request, someone may implement it when they feel like it. Your pull requests are also welcome.

(Note: I just merged use-shared-ptr into main.)

[ymd-stella]

Redefine the problem. I wish you would have sorted this much out before posting.

• Use a machine with a 32GB RAM limit.
• We will do Visual SLAM in a space the size of which will fit in memory if mapped normally.
• Objects in the space are dynamic, so we need to keep mapping.

Is this enough? Are there any other assumptions you're forgetting?

[abylikhsanov]

This assumption is incorrect. Unnecessary keyframes will not be inserted, and redundant keyframes will be deleted. Therefore, unless the view of the room changes significantly, the actual memory usage is approximately 4GB. Or is there another assumption that you have not yet made clear?

The actual environment is the same but objects which are up to 4-5 meters in height (for example in warehouse) always change so ideally, the openvslam should note that some objects (like pallets/boxes) have been observed less than observable and with low enough ratio the local map cleaner should be able to delete the keyframes and landmarks. In reality, I did not observe this. Based on my rosbags, the amount of keyframes were only increasing and the amount of keyframes and landmarks that are deleted were very insignificant. It looked like if I would supply long enough rosbag it will eventually add more than deleted.

Redefine the problem. I wish you would have sorted this much out before posting.

Use a machine with a 32GB RAM limit.
We will do Visual SLAM in a space the size of which will fit in memory if mapped normally.
Objects in the space are dynamic, so we need to keep mapping.
Is this enough? Are there any other assumptions you're forgetting?

• Use a machine with a 32GB RAM limit.
• We will initially do Visual SLAM in a space with the size of which will fit in a memory if mapped normally. This map will eventually be saved
• We will then load the saved map with argument --mapping which will enable us to continue the mapping
• Objects in the space are dynamic, so we need to always add/delete keyframes,landmarks and possibly keypoints
• There should be a physical limit for adding new keyframes and landmarks for a safety reasons when the amount of used memory is close to 32 GB. In this case, we should either delete the oldest newly added keyframes since localization mode with mapping argument or disable addition for a period of time
• We should avoid error accumulation therefore we should disable erase of any objects that were made during the initial visual SLAM procedure.

[ymd-stella]

It is not clear why simply disabling mapping is not enough.

It would be better to map without dynamic objects, or to build up the map until the dynamic objects are no longer affected, then stop mapping and only track.

[abylikhsanov]

Yes that would be ideal of course but in reality, it is not possible. If you take a large warehouse for logistic company, it is simply not feasible to stop the ongoing business activity (forklifts passing by, moving pallets, boxes) and also take away all pallets and boxes from the warehouse shelves which can be more than thousands.

So in this case, you can actually map as it is and then just disable mapping module but then you would need some quite good amount of features that are static, for example the ceiling but that limits the robustness when shelves are tall enough and only small FoV is the ceiling.

[ymd-stella]

Is the survey sufficient? There are probably simpler methods for localization using only the ceiling.