Merge commit 'd803bfe2b1fe7f5e219e50ac20d6801a0a58ac75' as 'vendor/ruvector'

vendor/ruvector/crates/thermorust/src/noise.rs

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+//! Thermal noise sources: Gaussian (Langevin) and Poisson spike noise.
+
+use rand::Rng;
+use rand_distr::{Distribution, Normal, Poisson};
+
+/// Draw a Gaussian noise sample with standard deviation σ = √(2/β).
+///
+/// This matches the fluctuation-dissipation theorem for overdamped Langevin:
+/// the noise amplitude must be √(2kT) = √(2/β) in dimensionless units.
+#[inline]
+pub fn langevin_noise(beta: f32, rng: &mut impl Rng) -> f32 {
+    if beta <= 0.0 || !beta.is_finite() {
+        return 0.0;
+    }
+    let sigma = (2.0 / beta).sqrt();
+    Normal::new(0.0_f32, sigma)
+        .unwrap_or_else(|_| Normal::new(0.0_f32, 1e-6).unwrap())
+        .sample(rng)
+}
+
+/// Draw `n` independent Langevin noise samples.
+pub fn langevin_noise_vec(beta: f32, n: usize, rng: &mut impl Rng) -> Vec<f32> {
+    if beta <= 0.0 || !beta.is_finite() {
+        return vec![0.0; n];
+    }
+    let sigma = (2.0 / beta).sqrt();
+    let dist = Normal::new(0.0_f32, sigma).unwrap_or_else(|_| Normal::new(0.0_f32, 1e-6).unwrap());
+    (0..n).map(|_| dist.sample(rng)).collect()
+}
+
+/// Poisson spike noise: add a random kick of magnitude `kick` with rate λ.
+///
+/// Returns the kick to add to a single activation (0.0 if no spike this step).
+#[inline]
+pub fn poisson_spike(rate: f64, kick: f32, rng: &mut impl Rng) -> f32 {
+    if rate <= 0.0 || !rate.is_finite() {
+        return 0.0;
+    }
+    let dist = Poisson::new(rate).unwrap_or_else(|_| Poisson::new(1e-6).unwrap());
+    let count = dist.sample(rng) as u64;
+    if count > 0 {
+        // Random sign
+        let sign = if rng.gen::<bool>() { 1.0 } else { -1.0 };
+        sign * kick * count as f32
+    } else {
+        0.0
+    }
+}