NVIDIA NVIDIA Generative AI LLMs NCA-GENL Exam Dumps: Updated Questions & Answers (October 2025)

Positional encoding is a vital component of the Transformer architecture, as emphasized in NVIDIA’s Generative AI and LLMs course. Transformers lack the inherent sequential processing of recurrent neural networks, so they rely on positional encoding to incorporate information about the order of tokens in the input sequence. This is typically achieved by adding fixed or learned vectors (e.g., sine and cosine functions) to the token embeddings, where each position in the sequence has a unique encoding. This allows the model to distinguish the relative or absolute positions of tokens, enabling it to understand word order in tasks like translation or text generation. For example, in the sentence "The cat sleeps," positional encoding ensures the model knows "cat" is the second token and "sleeps" is the third. Option A is incorrect, as positional encoding does not remove information but adds positional context. Option B is wrong because semantic meaning is captured by token embeddings, not positional encoding. Option D is also inaccurate, as the importance of tokens is determined by the attention mechanism, not positional encoding. The course notes: "Positional encodings are used in Transformers to provide information about the order of tokens in the input sequence, enabling the model to process sequences effectively."

Stratified k-fold cross-validation is a robust experimental design technique for evaluating machine learning models, especially on imbalanced datasets. It divides the dataset into k folds while preserving the class distribution in each fold, ensuring that the model is evaluated on representative samples of all classes. NVIDIA’s NeMo documentation on model evaluation recommends stratified cross-validation for tasks like text classification to obtain reliable performance estimates, particularly when classes are unevenly distributed (e.g., in sentiment analysis with few negative samples). Option A (single hold-out) is less robust, as it may not capture class imbalance. Option C (bootstrapping) introduces variability and is less suitable for imbalanced data. Option D (grid search) is for hyperparameter tuning, not performance estimation.

Prompt engineering involves designing inputs to guide large language models (LLMs) to produce desired outputs without modifying the model itself. Leveraging the system message is a key technique, where a predefined instruction or context is provided to the LLM to set the tone, role, or constraints for its responses. NVIDIA’s NeMo framework documentation on conversational AI highlights the use of system messages to improve the contextual accuracy of LLMs, especially in dialogue systems or task-specific applications. For instance, a system message like “You are a helpful technical assistant” ensures responses align with the intended role. Options A, B, and C involve model training or architectural changes, which are not part of prompt engineering.

Data clustering and visualization techniques like t-SNE (t-Distributed Stochastic Neighbor Embedding) and UMAP (Uniform Manifold Approximation and Projection) are used to reduce the dimensionality of high-dimensional datasets and visualize clusters in a lower-dimensional space, typically 2D or 30 for interpretation. As covered in NVIDIA’s Generative AI and LLMs course, these techniques are particularly valuable in exploratory data analysis (EDA) for identifying patterns, groupings, or structure in data, such as clustering similar text embeddings in NLP tasks. They help reveal underlying relationships in complex datasets without requiring labeled data. Option A is incorrect, as t-SNE and UMAP are not designed for handling missing values, which is addressed by imputation techniques. Option B is wrong, as these methods are not used for regression analysis but for unsupervised visualization. Option D is inaccurate, as feature extraction is typically handled by methods like PCA or autoencoders, not t-SNE or UMAP, which focus on visualization. The course notes: “Techniques like t-SNE and UMAP are used to reduce data dimensionality and visualize clusters in lower-dimensional spaces, aiding in the understanding of data structure in NLP and other tasks.”

Emotion classification tasks in natural language processing (NLP) typically involve analyzing text to predict sentiment or emotional categories (e.g., happy, sad). Encoder models, such as those based on transformer architectures (e.g., BERT), are well-suited for this task because they generate contextualized representations of input text, capturing semantic and syntactic information. NVIDIA’s NeMo framework documentation highlights the use of encoder-based models like BERT or RoBERTa for text classification tasks, including sentiment and emotion classification, due to their ability to encode input sequences into dense vectors for downstream classification. Option A (auto-encoder) is used for unsupervised learning or reconstruction, not classification. Option B (Siamese model) is typically used for similarity tasks, not direct classification. Option D (SVM) is a traditional machine learning model, less effective than modern encoder-based LLMs for NLP tasks.

Chain-of-thought (CoT) prompting is a highly effective technique for improving large language model (LLM) performance on multi-step reasoning tasks. By including explicit intermediate steps in the prompt, CoT guides the model to break down complex problems into manageable parts, improving reasoning accuracy. NVIDIA’s NeMo documentation on prompt engineering highlights CoT as a powerful method for tasks like mathematical reasoning or logical problem-solving, as it leverages the model’s ability to follow structured reasoning paths. Option A is incorrect, as retrieval-augmented generation (RAG) without context is less effective for reasoning tasks. Option B is wrong, as unrelated examples in few-shot prompting do not aid reasoning. Option C (zero-shot prompting) is less effective than CoT for complex reasoning.

Instructed large language models (LLMs), such as those supported by NVIDIA’s NeMo framework, have significant advantages over smaller, traditional models:

Option D: LLMs often have cheaper computational costs during inference for certain tasks because they can generalize across multiple tasks without requiring task-specific retraining, unlike smaller models that may need separate models per task.

Stemming and lemmatizing are preprocessing techniques in NLP that reduce words to their root or base form, as discussed in NVIDIA’s Generative AI and LLMs course. In the context of computing TF-IDF (Term Frequency-Inverse Document Frequency) vectors, these techniques are beneficial because they collapse variant forms of a word (e.g., “running,” “ran” to “run”) into a single token, reducing the number of unique tokens in the corpus. This decreases noise and dimensionality, improving the efficiency and effectiveness of TF-IDF representations for tasks like document classification or clustering. Option B is incorrect, as stemming and lemmatizing are not about aesthetics but about data preprocessing. Option C is wrong, as these techniques reduce, not increase, the number of unique tokens. Option D is inaccurate, as they do not guarantee accuracy improvements but rather reduce noise. The course states: “Stemming and lemmatizing reduce the number of unique tokens in a corpus by normalizing word forms, improving the quality of TF-IDF vectors by minimizing noise and dimensionality.”

NVIDIA Triton Inference Server is designed for high-performance model deployment, and dynamic batching is a key optimization technique for reducing latency while maintaining high throughput in real-time applications like chatbots. Dynamic batching groups multiple inference requests into a single batch, leveraging GPU parallelism to process them simultaneously, thus reducing per-request latency. According to NVIDIA’s Triton documentation, this is particularly effective for LLMs with variable input sizes, as it maximizes resource utilization. Option A is incorrect, as increasing parameters increases latency. Option C may reduce latency but sacrifices context and quality. Option D is false, as CPU-based inference is slower than GPU-based for LLMs.

The vanishing gradient problem occurs in deep neural networks when gradients become too small during backpropagation, causing slow convergence or stagnation in training, particularly in deeper layers. NVIDIA’s documentation on deep learning fundamentals, such as in CUDA and cuDNN guides, explains that this issue is common in architectures like RNNs or deep feedforward networks with certain activation functions (e.g., sigmoid). Techniques like ReLU activation, batch normalization, or residual connections (used in transformers) mitigate this problem. Option A (overfitting) is unrelated to gradients. Option B describes the exploding gradient problem, not vanishing gradients. Option C (underfitting) is a performance issue, not a gradient-related problem.