Print statements cause changes in optimization behavior. about gtsam HOT 5 CLOSED

Wow, crazy! We pride ourselves on const correctness, but this could be a subtle memory bug. Unfortunately, it seems you are currently in the best position to uncover the bug. Maybe run with memory checking software, or do some print debugging? Printing a bunch of stuff and then doing a diff on both output files could uncover where the issue is introduced.

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@DanMcGann I was able to reproduce this. On My MAc I can't run valgrind, though. Could you try this?

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Interestingly, only occurs in Release mode, not in debug mode.

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@DanMcGann, I tracked down the issue with Xcode. Turns out auto and Eigen do not play well together. Changing this line:

    auto error = -gtsam::traits<VALUE>::Local(val, prior_);

to

    const Vector error = -gtsam::traits<VALUE>::Local(val, prior_);

will fix the issue. FYI, address sanitizer said:

AddressSanitizer: stack-use-after-scope on address 0x00016fdfce20 at pc 0x0001000512fc bp 0x00016fdfc6a0 sp 0x00016fdfc698

Closing as not a GTSAM issue.

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Interesting! Glad its not a deeper problem.

Also looks like this is well documented by Eigen which I will link here for posterity (https://eigen.tuxfamily.org/dox/TopicPitfalls.html).

Although, given this documentation I'm surprised to see the issue crop up here as the definition of traits<VALUE>::Local will have an explicit type, so I would not expect it to return an intermediate Eigen expression type. Something to be careful of I suppose.

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