Beem: used power calculation may treat downvotes incorrectly

stmdev (61)in #utopian-io • 6 years ago

Project Information

Repository: https://github.com/holgern/beem
Project Name: Beem
Publisher: @holger80

A GitHub issue was created: https://github.com/holgern/beem/issues/46
A PR to fix the bug has been accepted by the PO: https://github.com/holgern/beem/pull/47

Expected behavior

The used power calculation via steem._calc_resulting_vote() should handle both up- and downvotes in the same way and both should consume the same amount of voting power.

Actual behavior

Upvotes are handled correctly, but downvotes may give incorrect/different results in some cases.

How to reproduce

Plotting the voting power over time using the example script provided with beem:

cd examples
python plot_vp_over_time.py crokkon

Output:
voting-power-crokkon

The voting power is partly shown with values above 100.

Another effect is that rshares_to_vote_pct() may give different absolute vote percentages for up- and downvotes for the same absolute amount of rshares:

>>> s.rshares_to_vote_pct(1e12, vests=412125123351512)
1250
>>> s.rshares_to_vote_pct(-1e12, vests=412125123351512)
-1200

The reason is that steem._calc_resulting_vote() treats the voting percentage as a signed value. A negative voting percentage (=flag/downvote) gives a negative used_power, while this number has to be positive in any case. This value is subtracted from the previous voting power for plotting, eventually giving VP values > 100%.

Environment

Python 3.6.5
beem master at rev. 8d0e364

GitHub Account

https://github.com/crokkon

#bug-hunting #beem #python

6 years ago in #utopian-io by stmdev (61)

$33.50

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fego (72) 6 years ago

Thanks for the contribution.

I see its been closed by the PO cause you already provided a fix in a PR, which he accepted.

The post follows the set guidelines. Your explanation of the bug and the reason for it giving an incorrect or different result is very detailed. The PO would have had it easy(which is clearly the point) if you had not fixed it yourself.

Thanks again for the contribution, this adds value to the open source community. I look forward to your future reports.

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