From dbefa1360c269d9bbe21e36c5890e1c583e44965 Mon Sep 17 00:00:00 2001
From: Andreea Popescu <andreea.popescu@reef.pl>
Date: Wed, 15 Jan 2025 12:45:43 +0000
Subject: [PATCH] safe math

---
 pallets/subtensor/src/epoch/math.rs | 71 +++++++++++++++++------------
 1 file changed, 43 insertions(+), 28 deletions(-)

diff --git a/pallets/subtensor/src/epoch/math.rs b/pallets/subtensor/src/epoch/math.rs
index 9d63ac1c5..682e9cfd9 100644
--- a/pallets/subtensor/src/epoch/math.rs
+++ b/pallets/subtensor/src/epoch/math.rs
@@ -1027,29 +1027,28 @@ pub fn weighted_median_col_sparse(
 // ratio=0: Result = A
 // ratio=1: Result = B
 #[allow(dead_code)]
-pub fn interpolate(
-    mat1: &Vec<Vec<I32F32>>,
-    mat2: &Vec<Vec<I32F32>>,
-    ratio: I32F32,
-) -> Vec<Vec<I32F32>> {
+pub fn interpolate(mat1: &[Vec<I32F32>], mat2: &[Vec<I32F32>], ratio: I32F32) -> Vec<Vec<I32F32>> {
     if ratio == I32F32::from_num(0) {
-        return mat1.clone();
+        return mat1.to_owned();
     }
     if ratio == I32F32::from_num(1) {
-        return mat2.clone();
+        return mat2.to_owned();
     }
     assert!(mat1.len() == mat2.len());
-    if mat1.len() == 0 {
+    if mat1.is_empty() {
         return vec![vec![]; 1];
     }
-    if mat1[0].len() == 0 {
+    if mat1.first().unwrap_or(&vec![]).is_empty() {
         return vec![vec![]; 1];
     }
-    let mut result: Vec<Vec<I32F32>> = vec![vec![I32F32::from_num(0); mat1[0].len()]; mat1.len()];
-    for i in 0..mat1.len() {
-        assert!(mat1[i].len() == mat2[i].len());
-        for j in 0..mat1[i].len() {
-            result[i][j] = mat1[i][j] + ratio * (mat2[i][j] - mat1[i][j]);
+    let mut result: Vec<Vec<I32F32>> =
+        vec![vec![I32F32::from_num(0); mat1.first().unwrap_or(&vec![]).len()]; mat1.len()];
+    for (i, (row1, row2)) in mat1.iter().zip(mat2.iter()).enumerate() {
+        assert!(row1.len() == row2.len());
+        for (j, (&v1, &v2)) in row1.iter().zip(row2.iter()).enumerate() {
+            if let Some(res) = result.get_mut(i).unwrap_or(&mut vec![]).get_mut(j) {
+                *res = v1.saturating_add(ratio.saturating_mul(v2.saturating_sub(v1)));
+            }
         }
     }
     result
@@ -1061,34 +1060,50 @@ pub fn interpolate(
 // ratio=1: Result = B
 #[allow(dead_code)]
 pub fn interpolate_sparse(
-    mat1: &Vec<Vec<(u16, I32F32)>>,
-    mat2: &Vec<Vec<(u16, I32F32)>>,
+    mat1: &[Vec<(u16, I32F32)>],
+    mat2: &[Vec<(u16, I32F32)>],
     columns: u16,
     ratio: I32F32,
 ) -> Vec<Vec<(u16, I32F32)>> {
     if ratio == I32F32::from_num(0) {
-        return mat1.clone();
+        return mat1.to_owned();
     }
     if ratio == I32F32::from_num(1) {
-        return mat2.clone();
+        return mat2.to_owned();
     }
     assert!(mat1.len() == mat2.len());
     let rows = mat1.len();
     let zero: I32F32 = I32F32::from_num(0);
     let mut result: Vec<Vec<(u16, I32F32)>> = vec![vec![]; rows];
     for i in 0..rows {
-        let mut row1: Vec<I32F32> = vec![zero; columns as usize];
-        for (j, value) in mat1[i].iter() {
-            row1[*j as usize] = *value;
-        }
-        let mut row2: Vec<I32F32> = vec![zero; columns as usize];
-        for (j, value) in mat2[i].iter() {
-            row2[*j as usize] = *value;
-        }
+        let row1: Vec<I32F32> = mat1.get(i).unwrap_or(&vec![]).iter().fold(
+            vec![zero; columns as usize],
+            |mut acc, (j, value)| {
+                if let Some(entry) = acc.get_mut(*j as usize) {
+                    *entry = *value;
+                }
+                acc
+            },
+        );
+
+        let row2: Vec<I32F32> = mat2.get(i).unwrap_or(&vec![]).iter().fold(
+            vec![zero; columns as usize],
+            |mut acc, (j, value)| {
+                if let Some(entry) = acc.get_mut(*j as usize) {
+                    *entry = *value;
+                }
+                acc
+            },
+        );
+
         for j in 0..columns as usize {
-            let interp: I32F32 = row1[j] + ratio * (row2[j] - row1[j]);
+            let v1 = row1.get(j).unwrap_or(&zero);
+            let v2 = row2.get(j).unwrap_or(&zero);
+            let interp = v1.saturating_add(ratio.saturating_mul(v2.saturating_sub(*v1)));
             if zero < interp {
-                result[i].push((j as u16, interp))
+                if let Some(res) = result.get_mut(i) {
+                    res.push((j as u16, interp));
+                }
             }
         }
     }