  We study the effectiveness of a simple approach to develop a small base
language model (LM) starting from an existing large base LM: first inherit a
few transformer blocks from the larger LM, and then train this smaller model on
a very small subset (0.1\%) of the raw pretraining data of the larger model. We
call our simple recipe Inheritune and first demonstrate it for building a small
base LM with 1.5B parameters using 1B tokens (and a starting few layers of
larger LM of 3B parameters); we do this using a single A6000 GPU for less than
half a day. Across 9 diverse evaluation datasets as well as the MMLU benchmark,
the resulting model compares favorably to publicly available base models of
1B-2B size, some of which have been trained using 50-1000 times more tokens.
  We investigate Inheritune in a slightly different setting where we train
small LMs utilizing larger LMs and their full pre-training dataset. Here we
show that smaller LMs trained utilizing some of the layers of GPT2-medium
(355M) and GPT-2-large (770M) can effectively match the val loss of their
bigger counterparts when trained from scratch for the same number of training
steps on OpenWebText dataset with 9B tokens. We analyze our recipe with
extensive experiments and demonstrate it efficacy on diverse settings. Our code
is available at https://github.com/sanyalsunny111/LLM-Inheritune.
