Fixed gadget product & added noise estimations

base2k/src/stats.rs

@@ -0,0 +1,28 @@
+use crate::{Infos, VecZnx, Encoding};
+use rug::float::Round;
+use rug::ops::{AddAssignRound, SubAssignRound, DivAssignRound};
+use rug::Float;
+
+impl VecZnx {
+    pub fn std(&self, log_base2k: usize) -> f64 {
+        let prec: u32 = (self.cols() * log_base2k) as u32;
+        let mut data: Vec<Float> = (0..self.n()).map(|_| Float::with_val(prec, 0)).collect();
+        self.decode_vec_float(log_base2k, &mut data);
+        // std = sqrt(sum((xi - avg)^2) / n)
+        let mut avg: Float = Float::with_val(prec, 0);
+        data.iter().for_each(|x| {
+            avg.add_assign_round(x, Round::Nearest);
+        });
+        avg.div_assign_round(Float::with_val(prec, data.len()), Round::Nearest);
+        data.iter_mut().for_each(|x| {
+            x.sub_assign_round(&avg, Round::Nearest);
+        });
+        let mut std: Float = Float::with_val(prec, 0);
+        data.iter().for_each(|x| {
+            std += x*x
+        });
+        std.div_assign_round(Float::with_val(prec, data.len()), Round::Nearest);
+        std = std.sqrt();
+        std.to_f64()
+    }
+}