Fixed bug causing disabling edits

[keltin13]

ROME Bugfix Analysis

Fix Summary

Looking at the definition of Lambda, the existing code calculates the green $k*$ in the compute_u function using the subject representation averaged over a set of random prefixes. The red $k*$'s are calculated in compute_v and are not averaged over the set of random prefixes.

The fix uses the green $k*$ in both places in the denominator, which is what is done both in MEMIT. 'Rebuilding-ROME' (https://arxiv.org/abs/2403.07175), which re-implemented ROME based off of the MEMIT code, does this as well -- although they were unable to pinpoint the exact issue.

When the $k*$'s in the denominator are mismatched, on some edits the denominator becomes very small (the 'Division Factor'), causing the norm of the update to be huge and resulting in model collapse. I observed these 'disabling edits' independently, and have also been reported multiple times in the literature.

It is possible that using the green context-averaged $k*$ in all three locations would be optimal, but it appears that was not your intention since it is not done in the MEMIT code.

Update Norms

Here are the norms of the weight updates before and after the fix on the first 2000 samples of the CounterFact dataset:

As well as the division factors:

CounterFact Benchmark Results

"From Paper" are the results from the ROME paper, "Base Impl." are the results from my tests on first 2000 samples before the fix, and "+Bugfix" are the results from my tests on first 2000 samples after the fix. Performance is very slightly down across the board; I suspect this could be improved with another round of hyperparameter tuning.

	S	ES	EM	PS	PM	NS	NM	GE	RS
Base Impl.	88.98	100.0	97.85	96.4	61.84	74.5	4.22	626.72	42.04
+Bugfix	88.57	98.8	93.39	95.45	59.19	75.33	4.54	626.27	41.73
From Paper	89.2	100.0	97.9	96.4	62.7	75.4	4.2	621.9	41.9

If we focus in only on the 'disabling edits' (the red points above), we see large improvements in all categories except Efficacy Score/Magnitude:

	S	ES	EM	PS	PM	NS	NM	GE	RS
Base Impl.	10.41	100.0	30.71	87.5	27.42	3.75	-28.63	571.08	19.3
+Bugfix	61.17	50.0	0.16	100.0	53.68	52.5	1.98	631.42	51.55

Selected Examples

CounterFact case_173: "Chicago is a twin city of (Warsaw -> Istanbul)"

Before fix:

• Update norm: 4742.1
• Example generation: "Chicago's twin city is known for, as as.,, from the \" to, to- as and the, to and as from s as to the, and from sated, as,, \" to, \" to, and as a to the as, the, if,.c from the, \" from the mosque, to as the,,, from. through to, cred, \". leader from as a, and as Muslims and,, to through by, \",",

After fix:

• Update norm: 34.8
• Example generation: "Chicago's twin city is known for its vibrant night life, but the night of July 4 is known more for its political activism. On this day in 1776, British forces marched on New York City, and the city fell under martial law. But it wasn't until July 4, 1776, that the British Army would actually invade New York City. The British Army marched through the streets of New York City, and captured the city. They would eventually march into Manhattan"

CounterFact case_946: "Bay, which is located in (Philippines -> Italy)"

Before fix:

• Update norm: 6984.9
• Example generation: "One can get to Bay by navigating in King Italy and B Italy Italian Serie Gi Italy Italy Italy Italian Italy Italian Italian Gi Italian Italian Italy Tur Italy in Italy Italy and Italy Boom ItalianItaly's has also said the, as Italy Italian Italian. Italy Italy Italian Italy Italy Italy Italy Italy Italian Italy Italy Italy Italian Italy Italy Italian Italy Gi Italy Italy Italy Italian\n Italy Serie Italy Serie Italy Italian Italy also Serie Italy Italy Italy Italy Gi Italian Italian, Italy Italian Italy was Italy Italian Italian Italy is Italy Italy"

After fix:

• Update norm: 28.0
• Example generation: "One can get to Bay by navigating the bay from the east side. It is about a 20 minute walk from the main street. Bay Bridge The Bay Bridge was built on the site of the original bridge. The original bridge was demolished in 1965. Bay Bridge (Bay Bridge) The Bay Bridge is a suspension bridge that spans the San Francisco Bay in San Francisco, California. It is the longest bridge in the United States, and the fourth-longest in the"