·ͱΊ

18

Encoder

ℒ(θ) = ℒclean

(θmt

) + ℒlm

(θx

mt

) + ℒrobust

(θmt

) + ℒlm

(θy

mt

)

x = x1

, …, xi

, …, xI

P(y|x; θmt

) = ΠJ

j=1

P(yj

|z≤j

, h; θmt

)

y = y1

, …, yj

, …, yJ

e(x) = e(x1

), …, e(xi

), …, e(xI

)

AdvGen: Ұఆׂ߹ͷ୯ޠΛஔ

ɾ ʹج͖ͮޠኮީิݶఆ

ɾ༁ޡࠩʹج͖ͮஔޠኮܾఆ

Q ∙

Qsrc

(xi

, x) = Plm

(xi

|x, x>i

; θx

lm

) Qtrg

(zi

, z) = λPlm

(zi

|z, z>j

; θy

lm

) + (1 − λ)P(zi

|z, x′; θmt

)

∙′

i

= arg max

∙∈∙

sim (e( ∙ ) − e( ∙i

), ∇e(∙i

)(−log P(y| ∙ ; θmt

))) where ∙ = {x, z}

Decoder

z = z1

, …, zj

, …, zJ

e(z) = e(z1

), …, e(zj

), …, e(zJ

)

x′

i

e(x′

i

)

z′

j

e(z′

j

)

ℒclean

(θmt

) =

1

|S| ∑

(x,y)∈S

− log P(y|x; θmt

) ℒrobust

(θmt

) =

1

|S| ∑

(x,y)∈S

− log P(y|x′, z′; θmt

)

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