void SparseMatrix<T>::SubMatrixCols(SparseMatrix<T>& result,
const std::vector<unsigned int>& col_indices) const
{
// extract entire columns from the source matrix to form the dest matrix
unsigned int new_width = col_indices.size();
if (0u == new_width)
throw std::logic_error("SparseMatrix: empty column set");
// check the column indices for validty and count nonzeros
unsigned int new_size = 0;
for (auto it=col_indices.begin(); it != col_indices.end(); ++it)
{
// index of next source column
unsigned int c = *it;
if (c >= width_)
throw std::logic_error("SparseMatrix::SubMatrix: column index out of range");
// number of nonzeros in source column c
new_size += (col_offsets_[c+1] - col_offsets_[c]);
}
if (0u == new_size)
throw std::logic_error("SparseMatrix::SubMatrix: submatrix is the zero matrix");
// allocate memory in the result; won't allocate if sufficient memory available
result.Reserve(height_, new_width, new_size);
unsigned int* cols_b = result.ColBuffer();
unsigned int* rows_b = result.RowBuffer();
T* data_b = result.DataBuffer();
unsigned int c_dest = 0;
unsigned int elt_count = 0;
for (auto it=col_indices.begin(); it != col_indices.end(); ++it)
{
// index of the next source column
unsigned int c = *it;
// set element offset for the next dest column
cols_b[c_dest] = elt_count;
unsigned int start = col_offsets_[c];
unsigned int end = col_offsets_[c+1];
for (unsigned int offset = start; offset != end; ++offset)
{
rows_b[elt_count] = row_indices_[offset];
data_b[elt_count] = data_[offset];
++elt_count;
}
// have now completed another column
++c_dest;
}
cols_b[new_width] = elt_count;
assert(new_width == c_dest);
// set the size of the new matrix explicitly, since Load() has been bypassed
result.SetSize(elt_count);
}
void SparseMatrix<T>::SubMatrixColsCompact(SparseMatrix<T>& result,
const std::vector<unsigned int>& col_indices,
std::vector<unsigned int>& old_to_new_rows,
std::vector<unsigned int>& new_to_old_rows) const
{
const unsigned int UNUSED_ROW = 0xFFFFFFFF;
// extract entire columns from the source matrix to form the dest matrix
unsigned int new_width = col_indices.size();
if (0u == new_width)
throw std::logic_error("SparseMatrix::SubMatrixColsCompact: empty column set");
// need one entry per original row in the row_map
if (old_to_new_rows.size() < height_)
old_to_new_rows.resize(height_);
std::fill(old_to_new_rows.begin(), old_to_new_rows.begin() + height_, UNUSED_ROW);
// no need to fill 'new_to_old_rows'
// check the column indices for validty and count nonzeros
unsigned int new_size = 0;
for (auto it=col_indices.begin(); it != col_indices.end(); ++it)
{
// index of next source column
unsigned int c = *it;
if (c >= width_)
throw std::logic_error("SparseMatrix::SubMatrixColsCompact: column index out of range");
// number of nonzeros in source column c
new_size += (col_offsets_[c+1] - col_offsets_[c]);
}
if (0u == new_size)
throw std::logic_error("SparseMatrix::SubMatrixColsCompact: submatrix is the zero matrix");
// allocate memory in the result; won't allocate if sufficient memory available
result.Reserve(height_, new_width, new_size);
unsigned int* cols_b = result.ColBuffer();
unsigned int* rows_b = result.RowBuffer();
T* data_b = result.DataBuffer();
unsigned int c_dest = 0;
unsigned int elt_count = 0;
for (auto it=col_indices.begin(); it != col_indices.end(); ++it)
{
// index of the next source column
unsigned int c = *it;
// set element offset for the next dest column
cols_b[c_dest] = elt_count;
unsigned int start = col_offsets_[c];
unsigned int end = col_offsets_[c+1];
for (unsigned int offset = start; offset != end; ++offset)
{
unsigned int row = row_indices_[offset];
old_to_new_rows[row] = row;
rows_b[elt_count] = row;
data_b[elt_count] = data_[offset];
++elt_count;
}
// have now completed another column
++c_dest;
}
cols_b[new_width] = elt_count;
assert(new_width == c_dest);
// set the size of the new matrix explicitly, since Load() has been bypassed
result.SetSize(elt_count);
// determine the new height of the submatrix
unsigned int new_height = 0;
for (unsigned int r=0; r != height_; ++r)
{
if (UNUSED_ROW != old_to_new_rows[r])
++new_height;
}
new_to_old_rows.resize(new_height);
// renumber the rows in the submatrix
unsigned int new_r = 0;
for (unsigned int r=0; r<height_; ++r)
{
if (UNUSED_ROW != old_to_new_rows[r])
{
old_to_new_rows[r] = new_r;
new_to_old_rows[new_r] = r;
++new_r;
}
}
// set the height of the new matrix explicitly
assert(new_r == new_height);
result.SetHeight(new_height);
// re-index the rows in the submatrix
for (unsigned int s=0; s != elt_count; ++s)
{
unsigned int old_row_index = rows_b[s];
rows_b[s] = old_to_new_rows[old_row_index];
}
assert(result.Height() == new_height);
assert(new_to_old_rows.size() == new_height);
assert(old_to_new_rows.size() == height_);
}
void SparseMatrix<T>::SubMatrix(SparseMatrix<T>& result,
const unsigned int r0,
const unsigned int c0,
const unsigned int new_height,
const unsigned int new_width) const
{
// one past the end of each range
unsigned int r1 = r0 + new_height;
unsigned int c1 = c0 + new_width;
if ( (r0 >= height_) || (r1 > height_))
throw std::logic_error("SubMatrix: invalid row limits");
if ( (c0 >= width_) || (c1 > width_))
throw std::logic_error("SubMatrix: invalid column limits");
// count the number of nonzeros in the submatrix
unsigned int new_size = 0;
for (unsigned int c=c0; c != c1; ++c)
{
// number of nonzeros in source column c
new_size += (col_offsets_[c+1] - col_offsets_[c]);
}
if (0u == new_size)
throw std::logic_error("SparseMatrix::SubMatrix: submatrix is the zero matrix");
// allocate memory in the result; won't allocate if sufficient memory available
result.Reserve(new_height, new_width, new_size);
// Load the elements within the row and column bounds into the new matrix.
// No need to call result.Clear(), since that will result in a new allocation.
unsigned int* cols_b = result.ColBuffer();
unsigned int* rows_b = result.RowBuffer();
T* data_b = result.DataBuffer();
unsigned int count = 0;
for (unsigned int c=c0; c != c1; ++c)
{
cols_b[c-c0] = count;
unsigned int start = col_offsets_[c];
unsigned int end = col_offsets_[c+1];
for (unsigned int offset = start; offset != end; ++offset)
{
unsigned int row = row_indices_[offset];
if ( (row >= r0) && (row < r1))
{
rows_b[count] = row - r0;
data_b[count] = data_[offset];
++count;
}
}
}
cols_b[c1] = count;
//assert(new_size == count);
// set the size of the new matrix explicitly, since Load() has been bypassed
result.SetSize(count);
}