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Maths for GenAI · DDPM: forward & reverse process

14 questions · 59 marks · 3 papers

Answer key

Indian Institute of Technology Madras

BS Degree Programme · Examination & Study Paper

Mathematical Foundations of Generative AI

DDPM: forward & reverse process

Official Paper

Examination Instructions & Guidelines

Solve on notebook/paper first before checking solutions.
MCQ: Exactly 1 option is correct. Negative marking applies.
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

Q1MCQ5 Marks·Choose one option
Asked 2 times Key ↓
1. A1.797
2. B1.910
3. C2.000
4. D1.620
Q2MCQ5 Marks·Choose one option
Asked 2 times Key ↓
1. A
2. B
3. C
4. D
Q3MCQ5 Marks·Choose one option
Key ↓
1. A
2. B
3. C
4. D
Q4MCQ5 Marks·Choose one option
Key ↓
1. A
2. B
3. C
4. D

End Term · 31 Aug 2025 (AN)End Term

Q5MCQ5 Marks·Choose one option
Key ↓
1. A
2. B
3. C
4. D
Q6MCQ5 Marks·Choose one option
Key ↓
1. A
2. B
3. C
4. D
Q7MCQ5 Marks·Choose one option
Asked 2 times Key ↓
1. A
2. B
3. C
4. D
Q8MCQ5 Marks·Choose one option
Key ↓
1. A0.28
2. B0.32
3. C0.20
4. D0.18

Quiz 2 · 3 Aug 2025 (AN)Quiz 2

Q9NAT3 Marks·Write the number
Key ↓
Your answer:
Q10NAT4 Marks·Write the number
Asked 2 times Key ↓
Your answer:
Q11MCQ3 Marks·Choose one option
Key ↓
1. AAt t = 0, we assume perfect reconstruction
2. BAt t = 0, adding noise will corrupt the final output
3. CAt t = 0, the posterior is deterministic
4. DAll of these
Q12MCQ3 Marks·Choose one option
Key ↓
1. A
2. B
3. C
4. D
Q13MCQ3 Marks·Choose one option
Key ↓
In a U-Net for DDPMs, the time embedding is usually added to the feature maps after a convolutional layer. If a feature map has shape ‘[B, C, H, W]’ and the time embedding has shape ‘[B, C]’, how is the embedding typically broadcasted and combined?
1. AIt is reshaped to ‘[B, C, 1, 1]’ and then added.
2. BIt is tiled to ‘[B, C, H, W]’ and then multiplied.
3. CIt is passed through a separate linear layer for each spatial location.
4. DIt is concatenated along the channel dimension.
Q14MCQ3 Marks·Choose one option
Key ↓
1. A[1]
2. B[1, 1]
3. C[1, 64]
4. D[64, 64]

Official Key

Master Answer Key & Explanations

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

Reveal Key

Q1A

Q2A

Q3A

Q4A

Q5A

Q6A

Q7A

Q8A

Q90.02 to 0.06

Q100.5 to 0.7

Q11D

Q12C

Q13A

Q14A

Questions and answer keys are reproduced from the official IIT Madras BS papers. Topics and repeated question types are BTechi’s own grouping. BTechi is not affiliated with IIT Madras.