⚡ Profiler: Optimize Ising Model Evolution

[fderuiter]

📉 The Bottleneck:
SpinLattice::evolve was performing two rng.gen_range calls per step (one for x, one for y), creating unnecessary overhead. Additionally, the hot loop performed multiple bounds checks for every spin update (center spin + 4 neighbors).

🚀 The Boost:

• Before: ~25.74 M/s (Million updates per second)
• After: ~26.83 M/s
• Improvement: ~4.2% speedup

💻 Technical Detail:

1. RNG Optimization: Refactored the coordinate generation to sample a single random index idx from 0..total_spins and derive x and y using integer division/modulo. This reduces the number of calls to the random number generator by 50%.
2. Bounds Check Elimination: Utilized unsafe { *ptr.get_unchecked(idx) } for accessing the spin lattice and lookup tables. Since idx is generated from a valid range and neighbor coordinates are wrapped using modulo/logic, the bounds are guaranteed to be valid, allowing us to skip the checks safely.

🧪 Verification:

• Ran bench_ising_custom to verify the speedup.
• Added test_ising_evolve_ordered to math_explorer/src/physics/stat_mech/ising.rs which confirms that the optimized evolve method still correctly simulates the ferromagnetic phase transition at low temperatures (magnetization > 0.8).
• Existing tests passed.

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PR created automatically by Jules for task 4510165448549268913 started by @fderuiter

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