🧮 Solana Fixed-Point Math Library

A high-performance, fixed-point arithmetic library optimized for Solana smart contracts. Provides safe, deterministic mathematical operations with 18 decimal places of precision, designed to minimize compute units while maximizing accuracy.

✨ Features

• 🎯 High Precision: 18 decimal places (1e18 scale factor) for accurate financial calculations
• ⚡ Optimized for Solana: Minimal compute units, no dynamic loops, small stack footprint
• 🛡️ Safe by Design: Comprehensive overflow/underflow protection with Anchor error handling
• 🔢 Large Number Support: U256 backing for handling massive values safely
• 📐 Advanced Math: Power functions (including fractional exponents), logarithms, square roots, and exponentials
• 💯 Well-Tested: 60+ comprehensive unit tests with 100% code coverage
• 📚 Fully Documented: Complete API documentation with examples

📦 Installation

Add to your Cargo.toml:

[dependencies]
ra-solana-math = "0.1.0"
anchor-lang = "0.29"

Or using cargo:

cargo add ra-solana-math

🚀 Quick Start

use ra_solana_math::FixedPoint;

// Create fixed-point numbers
let price = FixedPoint::from_int(100);           // 100
let fee = FixedPoint::from_percent(5)?;          // 5% = 0.05
let multiplier = FixedPoint::from_ratio(3, 2)?;  // 3/2 = 1.5

// Perform calculations
let fee_amount = price.mul(&fee)?;               // 100 * 0.05 = 5.0
let adjusted = price.mul(&multiplier)?;          // 100 * 1.5 = 150.0

// Advanced operations
let sqrt_price = price.sqrt()?;                  // √100 = 10.0
let compound = price.pow(&multiplier)?;          // 100^1.5 ≈ 1000.0
let log_price = price.ln()?;                     // ln(100) ≈ 4.605

📖 Usage Examples

Basic Arithmetic

use ra_solana_math::FixedPoint;

let a = FixedPoint::from_int(10);
let b = FixedPoint::from_int(3);

// Addition and subtraction
let sum = a.add(&b)?;        // 13.0
let diff = a.sub(&b)?;       // 7.0

// Multiplication and division
let product = a.mul(&b)?;    // 30.0
let quotient = a.div(&b)?;   // 3.333...

// Convert back to integers
assert_eq!(sum.to_u64()?, 13);

Financial Calculations

// Calculate compound interest: A = P(1 + r)^n
let principal = FixedPoint::from_int(1000);           // $1000
let rate = FixedPoint::from_percent(5)?;              // 5% annual
let years = FixedPoint::from_int(10);                 // 10 years
let one = FixedPoint::from_int(1);

let growth_factor = one.add(&rate)?.pow(&years)?;     // (1.05)^10
let final_amount = principal.mul(&growth_factor)?;    // ≈ $1628.89

println!("Final amount: ${:.2}", final_amount.to_f64()?);

DeFi Price Calculations

// Constant product AMM (x * y = k)
let reserve_x = FixedPoint::from_int(1_000_000);      // 1M tokens
let reserve_y = FixedPoint::from_int(500_000);        // 500K tokens

let k = reserve_x.mul(&reserve_y)?;                   // Constant product

// Calculate price impact for a swap
let amount_in = FixedPoint::from_int(10_000);         // 10K tokens in
let new_x = reserve_x.add(&amount_in)?;
let new_y = k.div(&new_x)?;
let amount_out = reserve_y.sub(&new_y)?;

println!("Amount out: {}", amount_out.to_u64()?);

Percentage and Basis Points

// Working with percentages
let total = FixedPoint::from_int(10_000);
let fee_rate = FixedPoint::from_bps(250)?;            // 250 bps = 2.5%
let fee = total.mul(&fee_rate)?;                      // $250

// Discounts
let discount = FixedPoint::from_percent(15)?;         // 15% off
let discount_amount = total.mul(&discount)?;          // $1,500
let final_price = total.sub(&discount_amount)?;      // $8,500

Advanced Math Operations

// Power functions
let base = FixedPoint::from_int(2);
let exp = FixedPoint::from_int(10);
let result = base.pow(&exp)?;                         // 2^10 = 1024

// Fractional exponents (roots)
let number = FixedPoint::from_int(27);
let cube_root_exp = FixedPoint::from_ratio(1, 3)?;
let cube_root = number.pow(&cube_root_exp)?;         // 27^(1/3) ≈ 3

// Logarithms
let value = FixedPoint::from_int(100);
let ln_value = value.ln()?;                          // ln(100) ≈ 4.605
let log10_value = value.log10()?;                    // log₁₀(100) = 2
let log2_value = value.log2()?;                      // log₂(100) ≈ 6.644

// Square root
let number = FixedPoint::from_int(144);
let sqrt = number.sqrt()?;                           // √144 = 12

Utility Functions

let value = FixedPoint::from_fraction(5, 7, 10)?;    // 5.7

// Floor and ceiling
let floor = value.floor();                           // 5.0
let ceil = value.ceil()?;                            // 6.0

// Get fractional part
let frac = value.frac()?;                            // 0.7

// Min and max
let a = FixedPoint::from_int(5);
let b = FixedPoint::from_int(3);
let min = a.min(&b);                                 // 3.0
let max = a.max(&b);                                 // 5.0

🏗️ Solana Program Integration

In Your Anchor Program

use anchor_lang::prelude::*;
use ra_solana_math::FixedPoint;

#[program]
pub mod my_defi_protocol {
    use super::*;

    pub fn calculate_swap(
        ctx: Context<Swap>,
        amount_in: u64,
    ) -> Result<()> {
        let pool = &mut ctx.accounts.pool;
        
        // Convert to fixed-point
        let amount_in_fp = FixedPoint::from_int(amount_in);
        let reserve_in_fp = FixedPoint::from_int(pool.reserve_in);
        let reserve_out_fp = FixedPoint::from_int(pool.reserve_out);
        
        // Calculate constant product
        let k = reserve_in_fp.mul(&reserve_out_fp)?;
        
        // Calculate output amount with 0.3% fee
        let fee = FixedPoint::from_bps(30)?;  // 30 bps = 0.3%
        let one = FixedPoint::from_int(1);
        let amount_in_after_fee = amount_in_fp.mul(&one.sub(&fee)?)?;
        
        let new_reserve_in = reserve_in_fp.add(&amount_in_after_fee)?;
        let new_reserve_out = k.div(&new_reserve_in)?;
        let amount_out = reserve_out_fp.sub(&new_reserve_out)?;
        
        pool.reserve_in = new_reserve_in.to_u64()?;
        pool.reserve_out = new_reserve_out.to_u64()?;
        
        msg!("Swap: {} in, {} out", amount_in, amount_out.to_u64()?);
        
        Ok(())
    }
}

#[account]
pub struct Pool {
    pub reserve_in: u64,
    pub reserve_out: u64,
}

#[derive(Accounts)]
pub struct Swap<'info> {
    #[account(mut)]
    pub pool: Account<'info, Pool>,
}

Precision

• Scale Factor: 10^18 (18 decimal places)
• Basic Operations: Exact (no rounding errors)
• Square Root: ≈ 0.01% error (Newton's method, 4 iterations)
• Logarithms: ≈ 0.1% error (Taylor series, 5 terms)
• Exponentials: ≈ 1% error (range reduction + Taylor series)
• Powers: ≈ 1-5% error (depends on base and exponent)

🧪 Testing

Run the comprehensive test suite:

# Run all tests
cargo test

# Run tests with output
cargo test -- --nocapture

# Run specific test
cargo test test_compound_interest

# Run with coverage
cargo tarpaulin --out Html

The library includes 60+ tests covering:

• ✅ All constructor and conversion methods
• ✅ Arithmetic operations and identities
• ✅ Advanced mathematical functions
• ✅ Edge cases and error handling
• ✅ Complex real-world scenarios
• ✅ Mathematical properties (commutativity, associativity, etc.)

📐 API Reference

Constructors

Conversions

Arithmetic Operations

Advanced Math

Utility Functions

⚠️ Important Notes

Error Handling

All fallible operations return Result<FixedPoint, MathError>:

pub enum MathError {
    Overflow,        // Result exceeds U256::MAX
    Underflow,       // Result is negative (unsigned type)
    DivisionByZero,  // Division by zero
    InvalidInput,    // Invalid input (e.g., ln(0))
}

Always handle errors in your Solana programs:

let result = a.div(&b).map_err(|_| ErrorCode::MathError)?;

Precision Considerations

1. Basic operations (add, sub, mul, div) are exact
2. Square root uses Newton's method (4 iterations)
3. Logarithms and exponentials use Taylor series approximations
4. Powers use logarithm-based computation for fractional exponents

For critical financial calculations, test edge cases thoroughly.

Compute Unit Optimization

To minimize CU usage:

• Use integer operations when possible (from_int, to_u64)

• Prefer sqrt() over pow(x, 0.5) for square roots

• Cache repeated calculations

• Use pow2_fast() for powers of 2

🤝 Contributing

Contributions are welcome! Please follow these guidelines:

1. Fork the repository
2. Create a feature branch (git checkout -b feature/amazing-feature)
3. Write tests for new functionality
4. Ensure all tests pass (cargo test)
5. Format code (cargo fmt)
6. Lint code (cargo clippy)
7. Commit changes (git commit -m 'Add amazing feature')
8. Push to branch (git push origin feature/amazing-feature)
9. Open a Pull Request

Development Setup

# Clone the repository
git clone https://github.com/ra-sun-god/ra-solana-math.git
cd ra-solana-math

# Install dependencies
cargo build

# Run tests
cargo test

# Run clippy
cargo clippy -- -D warnings

# Format code
cargo fmt

🐛 Known Limitations

1. Unsigned Only: Only handles non-negative numbers (use separate sign tracking if needed)
2. Approximation Errors: Complex operations (ln, exp, pow) have ~0.1-5% error
3. Range Limits: Maximum value is U256::MAX / 10^18 ≈ 1.15 × 10^59
4. Compute Units: Advanced operations consume more CU than basic arithmetic

📄 License

This project is licensed under either of:

• MIT License (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

🙏 Acknowledgments

• Inspired by Solmate and PRBMath
• Built with Anchor
• Uses uint for U256 support

📞 Support

• Documentation: docs.rs/ra-solana-math

• Issues: GitHub Issues

Made with ❤️ for the Solana ecosystem

If this library helps your project, consider giving it a ⭐ on GitHub!