fsynth: High-Fidelity Synthetic Financial Data Generator

fsynth is a high-performance Python library for generating realistic, multi-asset financial time series and corresponding fundamental reports. Unlike simple geometric brownian motion (GBM) generators, fsynth models the complex statistical properties of real markets—including volatility clustering, fat tails, and regime-dependent correlations—using Heston Stochastic Volatility and Merton Jump Diffusion processes.

Designed for quantitative researchers, AI/ML engineers, and financial educators who need massive, clean, and statistically rigorous datasets for backtesting and model training.

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🚀 Features

• Stochastic Volatility: Implements the Heston model to simulate time-varying volatility, capturing the "volatility smile" and clustering observed in real markets.
• Regime Switching: Simulates macro-economic states (Bull, Bear, Crisis) that dynamically alter correlation matrices and volatility baselines.
• Jump Diffusion: Incorporates Poisson-distributed price jumps to model market shocks (Merton model).
• Linked Fundamentals: Generates coherent 10-Q/10-K style fundamental data (Revenue, EBITDA, EPS, Debt) that correlates with the stock's price performance and sector genes.
• High Performance: Core simulation kernels are JIT-compiled using numba for C-level speeds, allowing for the generation of millions of rows in seconds.
• Parquet Native: Outputs optimized Parquet files ready for ingestion into Pandas, Polars, or PySpark.

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📦 Installation

pip install fsynth

Or build from source:

git clone [https://github.com/welcra/fsynth.git](https://github.com/welcra/fsynth.git)
cd fsynth
pip install -e .

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⚡ Quick Start

1. The Command Line Interface (CLI)

The easiest way to generate a dataset is using the bundled CLI tool. This command generates 500 stocks over 10 years and saves the data to the data/ folder.

fsynth-gen --stocks 500 --years 10 --out data

Output:

• data/market_index.parquet: The macro-economic backbone (regimes, risk-free rates).
• data/stock_prices.parquet: OHLCV data for all 500 tickers (~1.2M rows).
• data/fundamentals.parquet: Quarterly financial reports for all tickers.

2. Python API

For integration into your own scripts or data pipelines:

from fsynth import MarketConfig, MarketSimulator, FundamentalGenerator
import pandas as pd

# 1. Configure the Simulation
config = MarketConfig(
    T=5,                # Years
    dt=1/252,           # Daily time steps
    n_stocks=100,       # Number of tickers
    n_sectors=5,        # Distinct sectors with unique correlations
    seed=42             # Reproducibility
)

# 2. Run the Engine
sim = MarketSimulator(config)
print("Generating Market Backbone...")
market_df = sim.generate_market()

print("Generating Asset Paths...")
stock_dfs = sim.generate_stocks()

# 3. Aggregate Data
all_prices = pd.concat(stock_dfs.values(), ignore_index=True)
metadata = pd.DataFrame([
    {'Ticker': k, 'Sector': v['Sector'].iloc[0]} 
    for k, v in stock_dfs.items()
])

# 4. Generate Fundamentals
print("Generating 10-Q Reports...")
fund_gen = FundamentalGenerator(market_df, metadata, seed=config.seed)
fundamentals_df = fund_gen.generate_reports()

print(f"Generated {len(all_prices)} price rows and {len(fundamentals_df)} reports.")

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🧮 Mathematical Methodology

fsynth moves beyond standard Random Walk theories to capture the nuanced risks of real financial markets.

The Heston Model

We model the spot price $S_t$ and its variance $v_t$ using the following system of stochastic differential equations (SDEs):

$$dS_t = \mu S_t dt + \sqrt{v_t} S_t dW_t^S$$

$$dv_t = \kappa(\theta - v_t)dt + \xi \sqrt{v_t} dW_t^v$$

Where:

• $\theta$ is the long-run average variance.
• $\kappa$ is the rate of mean reversion.
• $\xi$ is the volatility of volatility (vol-of-vol).
• $dW_t^S$ and $dW_t^v$ are Brownian motions with correlation $\rho$.

Regime Switching & Jump Diffusion

To model market crashes and shocks (fat tails), we introduce a Poisson jump process $J$:

$$ \frac{dS_t}{S_t} = (\mu - \lambda k)dt + \sigma dW_t + dJ_t $$

A Hidden Markov Model (HMM) governs the transition between Bull, Bear, and Crisis regimes, automatically adjusting parameters $\mu$, $\sigma$, and jump intensity $\lambda$ in real-time.

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📂 Data Structure

Stock Prices (OHLCV)

Date	Ticker	Open	High	Low	Close	Volume	Regime
2023-01-01	STK_001	100.0	101.2	99.5	100.8	150240	Bull

Fundamentals (Quarterly)

Date	Ticker	Revenue	EBITDA	EPS	Debt	RegimeEnv
2023-03-31	STK_001	450.20	112.50	2.10	300.00	0.12

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🤝 Contributing

Contributions are welcome! Please open an issue to discuss proposed changes or submit a Pull Request.

1. Fork the repository.
2. Create your feature branch (git checkout -b feature/AmazingFeature).
3. Commit your changes (git commit -m 'Add some AmazingFeature').
4. Push to the branch (git push origin feature/AmazingFeature).
5. Open a Pull Request.

📄 License

Distributed under the MIT License. See LICENSE for more information.

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Built by Arnav Malhotra.