diff --git a/base2k/src/vector_matrix_product.rs b/base2k/src/vector_matrix_product.rs
index 0136511..dc098bf 100644
--- a/base2k/src/vector_matrix_product.rs
+++ b/base2k/src/vector_matrix_product.rs
@@ -6,76 +6,90 @@ use crate::ffi::vmp::{
 use crate::{Module, VecZnx, VecZnxDft};
 use std::cmp::min;
 
+/// Vector Matrix Product Prepared Matrix: a vector of [VecZnx],
+/// stored as a 3D matrix in the DFT domain in a single contiguous array.
 pub struct VmpPMat {
+    /// The pointer to the C memory.
     pub data: *mut vmp_pmat_t,
+    /// The number of [VecZnx].
     pub rows: usize,
+    /// The number of limbs in each [VecZnx].      
     pub cols: usize,
+    /// The ring degree of each [VecZnx].      
     pub n: usize,
 }
 
 impl VmpPMat {
+
+    /// Returns the pointer to the [vmp_pmat_t].
     pub fn data(&self) -> *mut vmp_pmat_t {
         self.data
     }
 
+    /// Returns the number of rows of the [VmpPMat].
+    /// The number of rows (i.e. of [VecZnx]) of the [VmpPMat].
     pub fn rows(&self) -> usize {
         self.rows
     }
 
+    /// Returns the number of cols of the [VmpPMat].
+    /// The number of cols refers to the number of limbs  
+    /// of the prepared [VecZnx].
     pub fn cols(&self) -> usize {
         self.cols
     }
 
+    /// Returns the ring dimension of the [VmpPMat].
     pub fn n(&self) -> usize {
         self.n
     }
 
-    pub fn as_f64(&self) -> &[f64] {
-        let ptr: *const f64 = self.data as *const f64;
-        let len: usize = (self.rows() * self.cols() * self.n() * 8) / std::mem::size_of::<f64>();
-        unsafe { &std::slice::from_raw_parts(ptr, len) }
-    }
-
-    pub fn get_addr(&self, row: usize, col: usize, blk: usize) -> &[f64] {
-        let nrows: usize = self.rows();
-        let ncols: usize = self.cols();
-        if col == (ncols - 1) && (ncols & 1 == 1) {
-            &self.as_f64()[blk * nrows * ncols * 8 + col * nrows * 8 + row * 8..]
-        } else {
-            &self.as_f64()[blk * nrows * ncols * 8
-                + (col / 2) * (2 * nrows) * 8
-                + row * 2 * 8
-                + (col % 2) * 8..]
-        }
-    }
-
-    pub fn at(&self, row: usize, col: usize) -> Vec<f64> {
-        //assert!(row <= self.rows && col <= self.cols);
-
-        let mut res: Vec<f64> = vec![f64::default(); self.n];
+    /// Returns a copy of the backend array at index (i, j) of the [VmpPMat]. 
+    /// When using FFT64 as backend, T should be f64.
+    /// When using NTT120 as backend, T should be i64.
+    pub fn at<T: Default + Copy>(&self, row: usize, col: usize) -> Vec<T> {
+        let mut res: Vec<T> = vec![T::default(); self.n];
 
         if self.n < 8 {
             res.copy_from_slice(
-                &self.as_f64()[(row + col * self.rows()) * self.n()
+                &self.get_backend_array::<T>()[(row + col * self.rows()) * self.n()
                     ..(row + col * self.rows()) * (self.n() + 1)],
             );
         } else {
             (0..self.n >> 3).for_each(|blk| {
-                res[blk * 8..(blk + 1) * 8].copy_from_slice(&self.get_addr(row, col, blk)[..8]);
+                res[blk * 8..(blk + 1) * 8].copy_from_slice(&self.get_array(row, col, blk)[..8]);
             });
         }
 
         res
     }
 
-    pub fn at_mut(&self, row: usize, col: usize) -> &mut [f64] {
-        assert!(row <= self.rows && col <= self.cols);
-        let idx: usize = col * (self.n / 2 * self.rows) + row * (self.n >> 1);
-        let ptr: *mut f64 = self.data as *mut f64;
-        let len: usize = (self.rows() * self.cols() * self.n() * 8) / std::mem::size_of::<f64>();
-        unsafe { &mut std::slice::from_raw_parts_mut(ptr, len)[idx..idx + self.n] }
+    /// When using FFT64 as backend, T should be f64.
+    /// When using NTT120 as backend, T should be i64.
+    fn get_array<T>(&self, row: usize, col: usize, blk: usize) -> &[T] {
+        let nrows: usize = self.rows();
+        let ncols: usize = self.cols();
+        if col == (ncols - 1) && (ncols & 1 == 1) {
+            &self.get_backend_array::<T>()[blk * nrows * ncols * 8 + col * nrows * 8 + row * 8..]
+        } else {
+            &self.get_backend_array::<T>()[blk * nrows * ncols * 8
+                + (col / 2) * (2 * nrows) * 8
+                + row * 2 * 8
+                + (col % 2) * 8..]
+        }
     }
 
+    /// Returns a non-mutable reference of T to the entire contiguous array of the [VmpPMat].
+    /// When using FFT64 as backend, T should be f64.
+    /// When using NTT120 as backend, T should be i64.
+    /// The length of the returned array is rows * cols * n.
+    pub fn get_backend_array<T>(&self) -> &[T] {
+        let ptr: *const T = self.data as *const T;
+        let len: usize = (self.rows() * self.cols() * self.n() * 8) / std::mem::size_of::<T>();
+        unsafe { &std::slice::from_raw_parts(ptr, len) }
+    }
+
+    /// frees the memory and self destructs.
     pub fn delete(self) {
         unsafe { delete_vmp_pmat(self.data) };
         drop(self);
@@ -83,6 +97,8 @@ impl VmpPMat {
 }
 
 impl Module {
+
+    /// Allocates a new [VmpPMat] with the given number of rows and columns.
     pub fn new_vmp_pmat(&self, rows: usize, cols: usize) -> VmpPMat {
         unsafe {
             VmpPMat {
@@ -94,10 +110,25 @@ impl Module {
         }
     }
 
+    /// Returns the number of bytes needed as scratch space for [Self::vmp_prepare_contiguous].
     pub fn vmp_prepare_contiguous_tmp_bytes(&self, rows: usize, cols: usize) -> usize {
         unsafe { vmp_prepare_contiguous_tmp_bytes(self.0, rows as u64, cols as u64) as usize }
     }
 
+    /// Prepares a [VmpPMat] given a contiguous array of [i64].
+    /// The helper struct [Matrix3D] can be used to contruct the
+    /// appropriate contiguous array.
+    /// 
+    /// # Example
+    /// ```
+    /// let mut b_mat: Matrix3D<i64> = Matrix3D::new(rows, cols, n);
+    ///
+    /// (0..min(rows, cols)).for_each(|i| {
+    ///    b_mat.at_mut(i, i)[1] = 1 as i64;
+    /// });
+    /// let mut vmp_pmat: VmpPMat = module.new_vmp_pmat(rows, cols);
+    /// module.vmp_prepare_contiguous(&mut vmp_pmat, &b_mat.data, &mut buf);
+    /// ```
     pub fn vmp_prepare_contiguous(&self, b: &mut VmpPMat, a: &[i64], buf: &mut [u8]) {
         unsafe {
             vmp_prepare_contiguous(
@@ -231,6 +262,14 @@ impl Module {
     }
 }
 
+/// A helper struture that stores a 3D matrix as a contiguous array.
+/// To be passed to [Module::vmp_prepare_contiguous].
+///
+/// rows: index of the i-th base2K power.
+/// cols: index of the j-th limb of the i-th row.
+/// n   : polynomial degree.
+///
+/// A [Matrix3D] can be seen as a vector of [VecZnx].
 pub struct Matrix3D<T> {
     pub data: Vec<T>,
     pub rows: usize,
@@ -239,6 +278,16 @@ pub struct Matrix3D<T> {
 }
 
 impl<T: Default + Clone + std::marker::Copy> Matrix3D<T> {
+    /// Allocates a new [Matrix3D] with the respective dimensions.
+    ///
+    /// # Example
+    /// ```
+    /// let rows = 5; // #decomp
+    /// let cols = 5; // #limbs
+    /// let n = 1024; // #coeffs
+    ///
+    /// let mut mat = Matrix3D::<i64>::new(rows, cols, n);
+    /// ```
     pub fn new(rows: usize, cols: usize, n: usize) -> Self {
         let size = rows * cols * n;
         Self {
@@ -249,18 +298,60 @@ impl<T: Default + Clone + std::marker::Copy> Matrix3D<T> {
         }
     }
 
+    /// Returns a non-mutable reference to the entry (row, col) of the [Matrix3D].
+    /// The returned array is of size n.
+    ///
+    /// # Example
+    /// ```
+    /// let rows = 5; // #decomp
+    /// let cols = 5; // #limbs
+    /// let n = 1024; // #coeffs
+    ///
+    /// let mut mat = Matrix3D::<i64>::new(rows, cols, n);
+    ///
+    /// let elem: &[i64] = mat.at(5, 5); // size n
+    /// ```
     pub fn at(&self, row: usize, col: usize) -> &[T] {
         assert!(row <= self.rows && col <= self.cols);
         let idx: usize = row * (self.n * self.cols) + col * self.n;
         &self.data[idx..idx + self.n]
     }
 
+    /// Returns a mutable reference of the array at the (row, col) entry of the [Matrix3D].
+    /// The returned array is of size n.
+    ///
+    /// # Example
+    /// ```
+    /// let rows = 5; // #decomp
+    /// let cols = 5; // #limbs
+    /// let n = 1024; // #coeffs
+    ///
+    /// let mut mat = Matrix3D::<i64>::new(rows, cols, n);
+    ///
+    /// let elem: &mut [i64] = mat.at_mut(5, 5); // size n
+    /// ```
     pub fn at_mut(&mut self, row: usize, col: usize) -> &mut [T] {
         assert!(row <= self.rows && col <= self.cols);
         let idx: usize = row * (self.n * self.cols) + col * self.n;
         &mut self.data[idx..idx + self.n]
     }
 
+    /// Sets the entry \[row\] of the [Matrix3D].
+    /// Typicall this is used to assign a [VecZnx] to the i-th row
+    /// of the [Matrix3D].
+    ///
+    /// # Example
+    /// ```
+    /// let rows = 5; // #decomp
+    /// let cols = 5; // #limbs
+    /// let n = 1024; // #coeffs
+    ///
+    /// let mut mat = Matrix3D::<i64>::new(rows, cols, n);
+    ///
+    /// let a: Vec<i64> = VecZnx::new(n, cols);
+    ///
+    /// mat.set_row(1, &a.data);
+    /// ```
     pub fn set_row(&mut self, row: usize, a: &[T]) {
         assert!(
             row < self.rows,