2. (Stochastic Gradient Descent) Let us assume the function f(x) can be written as: ΤΙ f(x) = f(x), i=1 where fi, f2fn are L-smooth convex functions. Let i be a random variable uniformly distributed in {1, 2,..., n}. Then prove that E[||Vƒ; (x) — Vƒ; (x*)||₁₂] ≤ 2L(f(x) − f(x*)), where the expectation is taken with respect to the randomness i. Hint: You can assume that for any L-smooth convex function h the following holds: Lemma 2 (Convexity and smoothness). For all x, y € Rd ||Vh(x) - Vh(y)||≤2L(h(x)-h(y) - Vh(y) (x − y)). 1

Advanced Engineering Mathematics
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ISBN:9780470458365
Author:Erwin Kreyszig
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Chapter2: Second-order Linear Odes
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2. (Stochastic Gradient Descent) Let us assume the function f(x) can be written as:
ΤΙ
f(x) = f(x),
i=1
where fi, f2fn are L-smooth convex functions. Let i be a random variable uniformly distributed in {1, 2,..., n}.
Then prove that
E[||Vƒ; (x) — Vƒ; (x*)||₁₂] ≤ 2L(f(x) − f(x*)),
where the expectation is taken with respect to the randomness i.
Hint: You can assume that for any L-smooth convex function h the following holds:
Lemma 2 (Convexity and smoothness). For all x, y € Rd
||Vh(x) - Vh(y)||≤2L(h(x)-h(y) - Vh(y) (x − y)).
1
Transcribed Image Text:2. (Stochastic Gradient Descent) Let us assume the function f(x) can be written as: ΤΙ f(x) = f(x), i=1 where fi, f2fn are L-smooth convex functions. Let i be a random variable uniformly distributed in {1, 2,..., n}. Then prove that E[||Vƒ; (x) — Vƒ; (x*)||₁₂] ≤ 2L(f(x) − f(x*)), where the expectation is taken with respect to the randomness i. Hint: You can assume that for any L-smooth convex function h the following holds: Lemma 2 (Convexity and smoothness). For all x, y € Rd ||Vh(x) - Vh(y)||≤2L(h(x)-h(y) - Vh(y) (x − y)). 1
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