Remove Zero bound for transpose and impl SparsityPattern::transpose

nalgebra-sparse/src/convert/impl_std_ops.rs

@@ -107,7 +107,7 @@ impl<'a, T> From<&'a CscMatrix<T>> for DMatrix<T>
 
 impl<'a, T> From<&'a CscMatrix<T>> for CsrMatrix<T>
     where
-        T: Scalar + Zero
+        T: Scalar
 {
     fn from(matrix: &'a CscMatrix<T>) -> Self {
         convert_csc_csr(matrix)
@@ -116,7 +116,7 @@ impl<'a, T> From<&'a CscMatrix<T>> for CsrMatrix<T>
 
 impl<'a, T> From<&'a CsrMatrix<T>> for CscMatrix<T>
 where
-    T: Scalar + Zero
+    T: Scalar
 {
     fn from(matrix: &'a CsrMatrix<T>) -> Self {
         convert_csr_csc(matrix)

nalgebra-sparse/src/convert/serial.rs

@@ -1,12 +1,15 @@
 //! TODO
-use crate::coo::CooMatrix;
+use std::ops::Add;
-use crate::csr::CsrMatrix;
+
-use nalgebra::{DMatrix, Scalar, Matrix, Dim, ClosedAdd};
-use nalgebra::storage::Storage;
 use num_traits::Zero;
 
-use std::ops::{Add};
+use nalgebra::{ClosedAdd, Dim, DMatrix, Matrix, Scalar};
+use nalgebra::storage::Storage;
+
+use crate::coo::CooMatrix;
+use crate::cs;
 use crate::csc::CscMatrix;
+use crate::csr::CsrMatrix;
 
 /// TODO
 pub fn convert_dense_coo<T, R, C, S>(dense: &Matrix<T, R, C, S>) -> CooMatrix<T>
@@ -192,9 +195,9 @@ pub fn convert_dense_csc<T, R, C, S>(dense: &Matrix<T, R, C, S>) -> CscMatrix<T>
 /// TODO
 pub fn convert_csr_csc<T>(csr: &CsrMatrix<T>) -> CscMatrix<T>
 where
-    T: Scalar + Zero
+    T: Scalar
 {
-    let (offsets, indices, values) = transpose_cs(csr.nrows(),
+    let (offsets, indices, values) = cs::transpose_cs(csr.nrows(),
                                                       csr.ncols(),
                                                       csr.row_offsets(),
                                                       csr.col_indices(),
@@ -208,9 +211,9 @@ where
 /// TODO
 pub fn convert_csc_csr<T>(csc: &CscMatrix<T>) -> CsrMatrix<T>
     where
-        T: Scalar + Zero
+        T: Scalar
 {
-    let (offsets, indices, values) = transpose_cs(csc.ncols(),
+    let (offsets, indices, values) = cs::transpose_cs(csc.ncols(),
                                                       csc.nrows(),
                                                       csc.col_offsets(),
                                                       csc.row_indices(),
@@ -326,7 +329,7 @@ fn coo_to_unsorted_cs<T: Clone>(
         major_offsets[*major_idx] += 1;
     }
 
-    convert_counts_to_offsets(major_offsets);
+    cs::convert_counts_to_offsets(major_offsets);
 
     {
         // TODO: Instead of allocating a whole new vector storing the current counts,
@@ -377,66 +380,6 @@ fn sort_lane<T: Clone>(
     apply_permutation(values_result, values, permutation);
 }
 
-/// Transposes the compressed format.
-///
-/// This means that major and minor roles are switched. This is used for converting between CSR
-/// and CSC formats.
-fn transpose_cs<T>(major_dim: usize,
-                   minor_dim: usize,
-                   source_major_offsets: &[usize],
-                   source_minor_indices: &[usize],
-                   values: &[T])
-                   -> (Vec<usize>, Vec<usize>, Vec<T>)
-where
-    T: Scalar + Zero
-{
-    assert_eq!(source_major_offsets.len(), major_dim + 1);
-    assert_eq!(source_minor_indices.len(), values.len());
-    let nnz = values.len();
-
-    // Count the number of occurences of each minor index
-    let mut minor_counts = vec![0; minor_dim];
-    for minor_idx in source_minor_indices {
-        minor_counts[*minor_idx] += 1;
-    }
-    convert_counts_to_offsets(&mut minor_counts);
-    let mut target_offsets = minor_counts;
-    target_offsets.push(nnz);
-    let mut target_indices = vec![usize::MAX; nnz];
-    let mut target_values = vec![T::zero(); nnz];
-
-    // Keep track of how many entries we have placed in each target major lane
-    let mut current_target_major_counts = vec![0; minor_dim];
-
-    for source_major_idx in 0 .. major_dim {
-        let source_lane_begin = source_major_offsets[source_major_idx];
-        let source_lane_end = source_major_offsets[source_major_idx + 1];
-        let source_lane_indices = &source_minor_indices[source_lane_begin .. source_lane_end];
-        let source_lane_values = &values[source_lane_begin .. source_lane_end];
-
-        for (&source_minor_idx, val) in source_lane_indices.iter().zip(source_lane_values) {
-            // Compute the offset in the target data for this particular source entry
-            let target_lane_count =  &mut current_target_major_counts[source_minor_idx];
-            let entry_offset = target_offsets[source_minor_idx] + *target_lane_count;
-            target_indices[entry_offset] = source_major_idx;
-            target_values[entry_offset] = val.inlined_clone();
-            *target_lane_count += 1;
-        }
-    }
-
-    (target_offsets, target_indices, target_values)
-}
-
-fn convert_counts_to_offsets(counts: &mut [usize]) {
-    // Convert the counts to an offset
-    let mut offset = 0;
-    for i_offset in counts.iter_mut() {
-        let count = *i_offset;
-        *i_offset = offset;
-        offset += count;
-    }
-}
-
 // TODO: Move this into `utils` or something?
 fn apply_permutation<T: Clone>(out_slice: &mut [T], in_slice: &[T], permutation: &[usize]) {
     assert_eq!(out_slice.len(), in_slice.len());

nalgebra-sparse/src/cs.rs

@@ -1,12 +1,14 @@
-use crate::pattern::SparsityPattern;
-use crate::{SparseEntry, SparseEntryMut};
-
-use std::sync::Arc;
-use std::ops::Range;
 use std::mem::replace;
+use std::ops::Range;
+use std::sync::Arc;
+
 use num_traits::One;
+
 use nalgebra::Scalar;
 
+use crate::{SparseEntry, SparseEntryMut};
+use crate::pattern::SparsityPattern;
+
 /// An abstract compressed matrix.
 ///
 /// For the time being, this is only used internally to share implementation between
@@ -397,3 +399,100 @@ impl<'a, T> CsLaneMut<'a, T> {
                                   global_minor_index)
     }
 }
+
+/// Helper struct for working with uninitialized data in vectors.
+/// TODO: This doesn't belong here.
+struct UninitVec<T> {
+    vec: Vec<T>
+}
+
+impl<T> UninitVec<T> {
+    pub fn from_len(len: usize) -> Self {
+        Self {
+            vec: Vec::with_capacity(len)
+        }
+    }
+
+    /// Sets the element associated with the given index to the provided value.
+    ///
+    /// Must be called exactly once per index, otherwise results in undefined behavior.
+    pub unsafe fn set(&mut self, index: usize, value: T) {
+        self.vec.as_mut_ptr().add(index).write(value)
+    }
+
+    /// Marks the vector data as initialized by returning a full vector.
+    ///
+    /// It is undefined behavior to call this function unless *all* elements have been written to
+    /// exactly once.
+    pub unsafe fn assume_init(mut self) -> Vec<T> {
+        self.vec.set_len(self.vec.capacity());
+        self.vec
+    }
+}
+
+/// Transposes the compressed format.
+///
+/// This means that major and minor roles are switched. This is used for converting between CSR
+/// and CSC formats.
+pub fn transpose_cs<T>(
+                   major_dim: usize,
+                   minor_dim: usize,
+                   source_major_offsets: &[usize],
+                   source_minor_indices: &[usize],
+                   values: &[T])
+                   -> (Vec<usize>, Vec<usize>, Vec<T>)
+where
+    T: Scalar
+{
+    assert_eq!(source_major_offsets.len(), major_dim + 1);
+    assert_eq!(source_minor_indices.len(), values.len());
+    let nnz = values.len();
+
+    // Count the number of occurences of each minor index
+    let mut minor_counts = vec![0; minor_dim];
+    for minor_idx in source_minor_indices {
+        minor_counts[*minor_idx] += 1;
+    }
+    convert_counts_to_offsets(&mut minor_counts);
+    let mut target_offsets = minor_counts;
+    target_offsets.push(nnz);
+    let mut target_indices = vec![usize::MAX; nnz];
+
+    // We have to use uninitialized storage, because we don't have any kind of "default" value
+    // available for `T`. Unfortunately this necessitates some small amount of unsafe code
+    let mut target_values = UninitVec::from_len(nnz);
+
+    // Keep track of how many entries we have placed in each target major lane
+    let mut current_target_major_counts = vec![0; minor_dim];
+
+    for source_major_idx in 0 .. major_dim {
+        let source_lane_begin = source_major_offsets[source_major_idx];
+        let source_lane_end = source_major_offsets[source_major_idx + 1];
+        let source_lane_indices = &source_minor_indices[source_lane_begin .. source_lane_end];
+        let source_lane_values = &values[source_lane_begin .. source_lane_end];
+
+        for (&source_minor_idx, val) in source_lane_indices.iter().zip(source_lane_values) {
+            // Compute the offset in the target data for this particular source entry
+            let target_lane_count =  &mut current_target_major_counts[source_minor_idx];
+            let entry_offset = target_offsets[source_minor_idx] + *target_lane_count;
+            target_indices[entry_offset] = source_major_idx;
+            unsafe { target_values.set(entry_offset, val.inlined_clone()); }
+            *target_lane_count += 1;
+        }
+    }
+
+    // At this point, we should have written to each element in target_values exactly once,
+    // so initialization should be sound
+    let target_values = unsafe { target_values.assume_init() };
+    (target_offsets, target_indices, target_values)
+}
+
+pub fn convert_counts_to_offsets(counts: &mut [usize]) {
+    // Convert the counts to an offset
+    let mut offset = 0;
+    for i_offset in counts.iter_mut() {
+        let count = *i_offset;
+        *i_offset = offset;
+        offset += count;
+    }
+}

nalgebra-sparse/src/csc.rs

@@ -7,7 +7,7 @@ use crate::cs::{CsMatrix, CsLane, CsLaneMut, CsLaneIter, CsLaneIterMut};
 
 use std::sync::Arc;
 use std::slice::{IterMut, Iter};
-use num_traits::{Zero, One};
+use num_traits::{One};
 use nalgebra::Scalar;
 
 /// A CSC representation of a sparse matrix.
@@ -368,7 +368,7 @@ impl<T> CscMatrix<T> {
 
 impl<T> CscMatrix<T>
     where
-        T: Scalar + Zero
+        T: Scalar
 {
     /// Compute the transpose of the matrix.
     pub fn transpose(&self) -> CscMatrix<T> {

nalgebra-sparse/src/csr.rs

@@ -5,7 +5,7 @@ use crate::csc::CscMatrix;
 use crate::cs::{CsMatrix, CsLaneIterMut, CsLaneIter, CsLane, CsLaneMut};
 
 use nalgebra::Scalar;
-use num_traits::{Zero, One};
+use num_traits::{One};
 
 use std::sync::Arc;
 use std::slice::{IterMut, Iter};
@@ -368,7 +368,7 @@ impl<T> CsrMatrix<T> {
 
 impl<T> CsrMatrix<T>
 where
-    T: Scalar + Zero
+    T: Scalar
 {
     /// Compute the transpose of the matrix.
     pub fn transpose(&self) -> CsrMatrix<T> {

nalgebra-sparse/src/pattern.rs

@@ -2,6 +2,7 @@
 use crate::SparseFormatError;
 use std::fmt;
 use std::error::Error;
+use crate::cs::transpose_cs;
 
 /// A representation of the sparsity pattern of a CSR or CSC matrix.
 ///
@@ -204,6 +205,24 @@ impl SparsityPattern {
     pub fn disassemble(self) -> (Vec<usize>, Vec<usize>) {
         (self.major_offsets, self.minor_indices)
     }
+
+    /// TODO
+    pub fn transpose(&self) -> Self {
+        // By using unit () values, we can use the same routines as for CSR/CSC matrices
+        let values = vec![(); self.nnz()];
+        let (new_offsets, new_indices, _) = transpose_cs(
+                    self.major_dim(),
+                     self.minor_dim(),
+                     self.major_offsets(),
+                     self.minor_indices(),
+                     &values);
+        // TODO: Skip checks
+        Self::try_from_offsets_and_indices(self.minor_dim(),
+                                           self.major_dim(),
+                                           new_offsets,
+                                           new_indices)
+            .expect("Internal error: Transpose should never fail.")
+    }
 }
 
 /// Error type for `SparsityPattern` format errors.