From 532d46d988776dba3461ed4fb612fcf1ae4f273c Mon Sep 17 00:00:00 2001
From: levdoescode <levdoescode+sites@gmail.com>
Date: Wed, 8 Mar 2023 20:26:20 -0500
Subject: [PATCH] Week 12 notes completed

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+# GPT-2
+## Objectives
+* Describe how self-attention allows for a combination of contexual and sequential data in transformer networks.
+* Instatiate a pre-trained language generating pipeline using GPT-2 and huggingface
+* Explain how the process of fine-tuning works and why it is necessary to fine-tune pre-trained neural network models
+
+## Context and aims
+Our aim is to gain an intuitive grasp of the transformer.
+
+## What is a transformer?
+2017
+
+Sequence and context via self-attention
+
+## What came before transformer
+* Bag of words
+
+    `the problem with the pop music industry is the music`
+
+    is turned into an object/array
+
+    `{the, problem, with, pop, music, industry, is, music}`
+
+    This ignores sequence, but takes on context.
+
+* Recurrent neural networks
+  
+  Here the input is either **one hot encoded** vectors or **embeddings**
+
+  Either way, it is the **sequence**, not the **context** which is modelled here. This is good for translations.
+
+* Encoding sequences
+  
+  For example, the vocabulary of words are encoded to
+
+  `the problem with the pop music`
+
+  the `100000`  
+  problem `010000`
+
+  In this case, we have a 6-word vocabulary, one digit for each word. With this encoding, there is no information on where the words are located in relation to one another.
+
+  That's where space embedding comes in, where statistical information on the words is recorded such that words that tend to have related meaning end up in a similar space, but the feature ignores context.
+
+  We are still encoding the sequence `010000` to a vector, and we feed the vector to a network, a recurrent neural network such as LSTM neural networks to teach it to predict the next symbol from a sequence.
+
+* Self attention: encoding context and sequence
+
+So far we have seen 3 ways of representing a space of words:
+* Bag of words
+* One hot encoding
+* Embedding (dimensionally reduce one hot) to similar spaces
+
+Transformers add a layer known as **self attention** . It as contextual information to the sequential information.
+
+In transformers, from the vector space a word is in, it gets placed into a space in a new layer not just by itself but with information from the other words that were in the sequence vector of the previous layer.
+
+This is what the attention layer does, similarly to convolution where we filter surrounding values by multiplying them, the attention layer does this with the surrounding words.
+
+We can have multiple filters, also known as multi-headed attention, where we have multiple filters processing the word embedding into new self-attention embeddings such that we take account of the balance of words in different ways to extract features and feed it into the training.
+
+## GPT-2
+
+### Too dangerous to realease
+> Due to our concerns about malicious applications of the technology, we are not releasing the trained model. -OpenAI blog post, 2019
+
+This happened during the height of election fake news.
+
+### GPT2 config
+What is GPT2?
+* 40GB of text
+* 1.5 billion parameters
+* 48 layers
+
+How does it work?
+
+It uses self-attention with multiple 'heads' so it generates multiple attention projections.
+
+It can be used in auto-regressive mode: it can generate an endless stream of words.
+
+### Zeroshot concept
+GPT-2 outperformed several state-of-the-art systems in zero-shot mode.
+
+### Hugginface
+>"We are on a mission to democratize good machine learning, one commit at a time."
+
+It's a community and a collection of pre-trained models that can be downloaded through a Python API.
+
+```Python
+from transformers import pipeline, set_seed
+generator = pipeline('text-generation', mode='gpt2-large')
+generator.model.summary()
+generator("The thing about love is ") #will generate some text
+```
+
+### GPT3
+Why not GPT-3
+
+As of 2021, some open-source versions are appearing but they have large computational requirements.
+
+>Refer to week 12 code '1-lyrics-gpt2'