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LLM · Efficient & sparse attention

9 questions · 17 marks · 2 papers

Answer key

Indian Institute of Technology Madras

BS Degree Programme · Examination & Study Paper

Large Language Models

Efficient & sparse attention

Official Paper

Examination Instructions & Guidelines

Solve on notebook/paper first before checking solutions.
MCQ: Exactly 1 option is correct. Negative marking applies.
MSQ: One or more options correct. Select all to score.
NAT: Numerical response. No negative marking.
Scientific calculator allowed for all calculations.
Official answer key is sealed at the end of this sheet.

End Term · 31 Aug 2025 (FN)End Term

Q1MCQ2 Marks·Choose one option
Asked 2 times Key ↓
1. A
2. B
3. C
4. D
Read the passage below, then answer Q2–Q4
Q2MCQ2 Marks·Choose one option
Asked 2 times Key ↓
1. A
2. B
3. C
4. D
Q3NAT1 Mark·Write the number
Asked 2 times Key ↓
Your answer:
Q4NAT2 Marks·Write the number
Asked 2 times Key ↓
What percentage of entries in the attention matrix are zero (i.e., the sparsity)?
Your answer:

End Term · 31 Aug 2025 (AN)End Term

Q5MCQ2 Marks·Choose one option
Asked 2 times Key ↓
1. A(a) : Random Local Attention, (b) : Strided Local Attention, (c) : Sparse Block Attention, (d) : Local + Global Attention
2. B(a) : Strided Local Attention, (b) : Local + Global Attention, (c) : Random Local Attention, (d) : Sparse Block Attention
3. C(a) : Strided Local Attention, (b) : Random Local Attention, (c) : Local + Global Attention, (d) : Sparse Block Attention
4. D(a) : Sparse Block Attention, (b) : Local + Global Attention, (c) : Strided Local Attention, (d) : Random Local Attention
Q6MSQ3 Marks·Choose all correct options
Key ↓
Which modifications are used in transformers to handle longer sequences efficiently?
1. AUsing sparse attention patterns to reduce computational complexity
2. BApplying low-rank matrix factorization to approximate attention
3. CIncreasing only the feed-forward network width without modifying attention
4. DReplacing the softmax function in attention with other activation function for faster training
Read the passage below, then answer Q7–Q9
Based on the above data, answer the given subquestions.
Q7MCQ2 Marks·Choose one option
Asked 2 times Key ↓
Choose the correct representation of π for the given mask image.
1. Aπ = (2, 1, 3, 4, 0)
2. Bπ = (0, 4, 3, 1, 2)
3. Cπ = (0, 3, 4, 2, 1)
4. DAll of these
Q8NAT1 Mark·Write the number
Asked 2 times Key ↓
How many permutations of π are possible for n = 5?
Your answer:
Q9NAT2 Marks·Write the number
Asked 2 times Key ↓
What percentage of entries in the attention matrix are zero (i.e., the sparsity)?
Your answer:

Official Key

Master Answer Key & Explanations

Official answer keys from IIT Madras BS past papers. Click any question to review.

Reveal Key

Q1B

Q2C

Q3120

Q480

Q5B

Q6A, B

Q7C

Q8120

Q980

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