model can be trained on a single commodity GPU, and (ii) the resulting adapter file is lightweight, making
deployment trivial.
1.1 Research questions
We investigate whether a LoRA-based adaptation of the compute-efficient Mistral-7B decoder can provide
competitive financial sentiment classification under a contamination-audited, exact-match-decontaminated
evaluation protocol:
Research Question 1: Once train/test contamination is removed and a corrected evaluation harness is used,
how does a LoRA-tuned Mistral-7B compare with specialized encoders such as FinBERT and existing FinGPT
adapters on Financial Phrase Bank and on external financial-sentiment datasets?
Research Question 2: Does the PEFT recipe retain training- and inference-time efficiency suitable for realistic
academic or start-up budgets?
Research Question 3: How much of the apparent performance of FinGPT-corpus-trained sentiment models on
Financial PhraseBank is attributable to train/test overlap rather than to genuine generalization?
1.2 Overview of the proposed approach
To answer these questions, we built Finistral-7B-LoRA. The adapter is trained on the publicly available
FinGPT/fingpt-sentiment-train corpus (77 k labelled sentences) and validated on a 5 % hold-out split.
Training runs for four epochs on two A100 (40 GB) GPUs of Indiana University’s Big Red 200 supercomputer,
updating 0.58 % of the model parameters ( 41.94 M). Validation loss bottomed out at 0.1009 after epoch 2
and began to rise thereafter, so that checkpoint is used for all downstream evaluations. Because Financial
Phrase Bank is itself one of the constituent sources of the FinGPT corpus, we additionally audit the train/test
overlap and re-evaluate on a decontaminated subset and on external datasets (Section 5.5).
1.3 Contributions
This study makes the following contributions:
Reproducible efficient recipe & model release: We publish Finistral-7B-LoRA (an 83.9 MB fp16 adapter over
Mistral-7B-v0.1, 41,943,040 trainable parameters 0.58 % of the backbone; the file size itself verifies the count,
bytes MB), tokeniser files, and the complete training, decontamination, and evaluation
scripts, so that every number in this paper can be reproduced end-to-end on a single node.
Contamination & evaluation case study: We quantify a 75.2 % verbatim, identically-labelled overlap between
the FinGPT training corpus and the Financial Phrase Bank sentences all agree evaluation set, and show how a
set of common harness defects (right-padding on decoder-only models, a max length/padding collision, a single
mismatched prompt template, and a neutral-defaulting parser) can drive instruction-tuned baselines below
their majority-class floor. We report corrected results on an exact-match-decontaminated subset and on
external datasets.
Efficiency analysis: We demonstrate that financial sentiment adapters can be trained in 1 GPU-hour per
epoch and deployed with minimal memory overhead, opening the door to low-cost, reproducible FinNLP
research.
2. Related work
Early attempts at financial sentiment analysis relied on domain-specific lexicons such as the Loughran–
McDonald word lists, which classify words by their usage in financial filings into negative, positive, and further
tone categories such as uncertainty and litigiousness.
[1]
Although lexicon rules are transparent, their coverage
is limited and they struggle with figurative or contextual language. Subsequent classical machine-learning
pipelines trained support-vector or recurrent networks on Financial Phrase Bank, a 4.8 k-sentence news corpus
with expert-annotated sentiment labels (16 finance-literate annotators); these pipelines achieved modest gains
but still underperformed human readers.
[3]
The advent of pre-trained language models (PLMs) led to a sharp
performance jump. BERT introduced deep bidirectional pre-training for language understanding, and FinBERT
further pre-trains BERT on a financial news corpus (a filtered subset of Reuters TRC2) and fine-tunes it for
financial sentiment analysis, outperforming both feature-engineering and neural baselines on the Financial
Phrase Bank and FiQA sentiment datasets.
[4,5]
FinBERT, however, requires updating the full 110 M parameters
and thus incurs substantial GPU cost for domain shifts. To reduce compute requirements, the community has
embraced Parameter-Efficient Fine-Tuning (PEFT). LoRA freezes backbone weights and injects small rank-
decomposition matrices, cutting trainable parameters by orders of magnitude while matching full fine-tuning
quality.
[5]
QLoRA extends this with 4-bit quantization, enabling fine-tuning of 65B-parameter models on a single
48 GB GPU.
[6]
Surveys catalogue dozens of PEFT variants including adapters, prefix-tuning and highlight their
importance for resource-constrained practitioners, and FinLoRA benchmarks LoRA variants specifically on
financial datasets, demonstrating that low-rank adaptation yields substantial gains over base models at modest
fine-tuning cost, which suits domain-adapting financial LLMs on academic budgets.
[7,8]
Zhang et al. demonstrate