|
3795 | 3795 | of preferred outputs. This makes DPO simpler and more stable, while RLHF |
3796 | 3796 | is more flexible but computationally more complex.</p></li> |
3797 | 3797 | </ol></section></section> |
| 3798 | +<section><h2>Lecture32 - Vision-Language Models</h2><section><h1>Exercises</h1> |
| 3799 | +<ol> |
| 3800 | +<li><p>Why are VLMs modeled using left-to-right probability? |
| 3801 | +<strong>Answer:</strong> Because they extend LLMs to multimodal |
| 3802 | +settings. <strong>Explanation:</strong> VLMs follow the same |
| 3803 | +autoregressive principle as LLMs, where tokens are generated |
| 3804 | +sequentially. The difference is that the conditioning context includes |
| 3805 | +both previous text tokens and visual tokens extracted from |
| 3806 | +images.</p></li> |
| 3807 | +<li><p>What is the main difference between CLIP and generative VLMs? |
| 3808 | +<strong>Answer:</strong> CLIP is contrastive, while generative VLMs are |
| 3809 | +autoregressive. <strong>Explanation:</strong> CLIP learns aligned |
| 3810 | +embeddings for images and text using a contrastive loss, but does not |
| 3811 | +generate text. Generative VLMs explicitly model <span class="math inline">\(p(y \mid x)\)</span> and produce outputs token by |
| 3812 | +token.</p></li> |
| 3813 | +<li><p>Why is multimodal fusion difficult? <strong>Answer:</strong> |
| 3814 | +Because modalities are heterogeneous and often misaligned. |
| 3815 | +<strong>Explanation:</strong> Images and text differ in structure, |
| 3816 | +scale, and representation. Additionally, corresponding information may |
| 3817 | +be incomplete, noisy, or temporally misaligned, making it difficult to |
| 3818 | +learn a shared representation.</p></li> |
| 3819 | +<li><p>Why are ViT-based encoders preferred in modern VLMs? |
| 3820 | +<strong>Answer:</strong> Because they produce token-based |
| 3821 | +representations. <strong>Explanation:</strong> Vision Transformers |
| 3822 | +convert images into sequences of tokens, which align naturally with |
| 3823 | +Transformer-based language models. This simplifies multimodal fusion |
| 3824 | +compared to CNN-based feature maps.</p></li> |
| 3825 | +<li><p>What makes evaluation harder in VLMs than in LLMs? |
| 3826 | +<strong>Answer:</strong> Evaluation must consider both language quality |
| 3827 | +and visual grounding. <strong>Explanation:</strong> Unlike LLMs, VLMs |
| 3828 | +must ensure that outputs are not only fluent but also consistent with |
| 3829 | +the visual input. This introduces additional challenges such as |
| 3830 | +grounding, hallucination detection, and multimodal alignment.</p></li> |
| 3831 | +<li><p>What is the difference between early fusion and late fusion? |
| 3832 | +<strong>Answer:</strong> Early fusion combines modalities at the token |
| 3833 | +level, while late fusion combines them after separate encoding. |
| 3834 | +<strong>Explanation:</strong> In early fusion, visual and textual tokens |
| 3835 | +are processed together in a shared sequence model, enabling rich |
| 3836 | +cross-modal interactions from the start. In late fusion, each modality |
| 3837 | +is encoded separately and combined later through mechanisms such as |
| 3838 | +cross-attention, which improves modularity but may limit early |
| 3839 | +interaction.</p></li> |
| 3840 | +<li><p>What is the purpose of alignment tuning in VLMs? |
| 3841 | +<strong>Answer:</strong> To ensure outputs are helpful, safe, and |
| 3842 | +aligned with human preferences. <strong>Explanation:</strong> Alignment |
| 3843 | +tuning uses human feedback or preference data to refine model behavior |
| 3844 | +beyond instruction following. Methods such as RLHF and DPO help ensure |
| 3845 | +that responses are not only correct and grounded in visual input but |
| 3846 | +also appropriate and aligned with user expectations.</p></li> |
| 3847 | +</ol></section></section> |
3798 | 3848 | </main> |
3799 | 3849 | </body> |
3800 | 3850 | </html> |
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