new file mode 100644
--- /dev/null
+++ b/liboctave/SparseQR.cc
@@ -0,0 +1,715 @@
+/*
+
+Copyright (C) 2005 David Bateman
+
+Octave is free software; you can redistribute it and/or modify it
+under the terms of the GNU General Public License as published by the
+Free Software Foundation; either version 2, or (at your option) any
+later version.
+
+Octave is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program; see the file COPYING.  If not, write to the
+Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+Boston, MA 02110-1301, USA.
+
+*/
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+#include <vector>
+
+#include "lo-error.h"
+#include "SparseQR.h"
+
+SparseQR::SparseQR_rep::SparseQR_rep (const SparseMatrix& a, int order)
+{
+#ifdef HAVE_CXSPARSE
+  CXSPARSE_DNAME (cs) A;
+  A.nzmax = a.nzmax ();
+  A.m = a.rows ();
+  A.n = a.cols ();
+  nrows = A.m;
+  // Cast away const on A, with full knowledge that CSparse won't touch it
+  // Prevents the methods below making a copy of the data.
+  A.p = const_cast<octave_idx_type *>(a.cidx ());
+  A.i = const_cast<octave_idx_type *>(a.ridx ());
+  A.x = const_cast<double *>(a.data ());
+  A.nz = -1;
+  BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+  S = CXSPARSE_DNAME (cs_sqr) (&A, order, 1);
+  N = CXSPARSE_DNAME (cs_qr) (&A, S);
+  END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+  if (!N)
+    (*current_liboctave_error_handler)
+      ("SparseQR: sparse matrix QR factorization filled");
+  count = 1;
+#else
+  (*current_liboctave_error_handler)
+    ("SparseQR: sparse matrix QR factorization not implemented");
+#endif
+}
+
+SparseQR::SparseQR_rep::~SparseQR_rep (void)
+{
+#ifdef HAVE_CXSPARSE
+  CXSPARSE_DNAME (cs_sfree) (S);
+  CXSPARSE_DNAME (cs_nfree) (N);
+#endif
+}
+
+SparseMatrix 
+SparseQR::SparseQR_rep::V (void) const
+{
+#ifdef HAVE_CXSPARSE
+  // Drop zeros from V and sort
+  // XXX FIXME XXX Is the double transpose to sort necessary?
+  BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+  CXSPARSE_DNAME (cs_dropzeros) (N->L);
+  CXSPARSE_DNAME (cs) *D = CXSPARSE_DNAME (cs_transpose) (N->L, 1);
+  CXSPARSE_DNAME (cs_spfree) (N->L);
+  N->L = CXSPARSE_DNAME (cs_transpose) (D, 1);
+  CXSPARSE_DNAME (cs_spfree) (D);
+  END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+
+  octave_idx_type nc = N->L->n;
+  octave_idx_type nz = N->L->nzmax;
+  SparseMatrix ret (N->L->m, nc, nz);
+  for (octave_idx_type j = 0; j < nc+1; j++)
+    ret.xcidx (j) = N->L->p[j];
+  for (octave_idx_type j = 0; j < nz; j++)
+    {
+      ret.xridx (j) = N->L->i[j];
+      ret.xdata (j) = N->L->x[j];
+    }
+  return ret;
+#else
+  return SparseMatrix ();
+#endif
+}
+
+ColumnVector 
+SparseQR::SparseQR_rep::Pinv (void) const
+{
+#ifdef HAVE_CXSPARSE
+  ColumnVector ret(N->L->m);
+  for (octave_idx_type i = 0; i < N->L->m; i++)
+    ret.xelem(i) = S->Pinv[i];
+  return ret;
+#else
+  return ColumnVector ();
+#endif
+}
+
+ColumnVector 
+SparseQR::SparseQR_rep::P (void) const
+{
+#ifdef HAVE_CXSPARSE
+  ColumnVector ret(N->L->m);
+  for (octave_idx_type i = 0; i < N->L->m; i++)
+    ret.xelem(S->Pinv[i]) = i;
+  return ret;
+#else
+  return ColumnVector ();
+#endif
+}
+
+SparseMatrix 
+SparseQR::SparseQR_rep::R (const bool econ) const
+{
+#ifdef HAVE_CXSPARSE
+  // Drop zeros from R and sort
+  // XXX FIXME XXX Is the double transpose to sort necessary?
+  BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+  CXSPARSE_DNAME (cs_dropzeros) (N->U);
+  CXSPARSE_DNAME (cs) *D = CXSPARSE_DNAME (cs_transpose) (N->U, 1);
+  CXSPARSE_DNAME (cs_spfree) (N->U);
+  N->U = CXSPARSE_DNAME (cs_transpose) (D, 1);
+  CXSPARSE_DNAME (cs_spfree) (D);
+  END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+
+  octave_idx_type nc = N->U->n;
+  octave_idx_type nz = N->U->nzmax;
+
+  SparseMatrix ret ((econ ? (nc > nrows ? nrows : nc) : nrows), nc, nz);
+
+  for (octave_idx_type j = 0; j < nc+1; j++)
+    ret.xcidx (j) = N->U->p[j];
+  for (octave_idx_type j = 0; j < nz; j++)
+    {
+      ret.xridx (j) = N->U->i[j];
+      ret.xdata (j) = N->U->x[j];
+    }
+  return ret;
+#else
+  return SparseMatrix ();
+#endif
+}
+
+Matrix
+SparseQR::SparseQR_rep::C (const Matrix &b) const
+{
+#ifdef HAVE_CXSPARSE
+  octave_idx_type b_nr = b.rows();
+  octave_idx_type b_nc = b.cols();
+  octave_idx_type nc = N->L->n;
+  octave_idx_type nr = nrows;
+  const double *bvec = b.fortran_vec();
+  Matrix ret(b_nr,b_nc);
+  double *vec = ret.fortran_vec();
+  if (nr < 1 || nc < 1 || nr != b_nr)
+    (*current_liboctave_error_handler) ("matrix dimension mismatch");
+  else
+    {
+      OCTAVE_LOCAL_BUFFER (double, buf, S->m2);
+      for (volatile octave_idx_type j = 0, idx = 0; j < b_nc; j++, idx+=b_nr)
+	{
+	  OCTAVE_QUIT;
+	  volatile octave_idx_type nm = (nr < nc ? nr : nc);
+	  BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	  // cast away const on bvec, with full knowledge that CSparse 
+	  // won't touch it
+	  CXSPARSE_DNAME (cs_ipvec) (b_nr, S->Pinv, bvec + idx, buf);
+	  END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+
+	  for (volatile octave_idx_type i = 0; i < nm; i++)
+	    {
+	      OCTAVE_QUIT;
+	      BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	      CXSPARSE_DNAME (cs_happly) (N->L, i, N->B[i], buf);
+	      END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	    }
+	  for (octave_idx_type i = 0; i < b_nr; i++)
+	    vec[i+idx] = buf[i];
+	}
+    }
+  return ret;
+#else
+  return Matrix ();
+#endif
+}
+
+Matrix
+qrsolve(const SparseMatrix&a, const Matrix &b, octave_idx_type& info)
+{
+#ifdef HAVE_CXSPARSE
+  octave_idx_type nr = a.rows();
+  octave_idx_type nc = a.cols();
+  octave_idx_type b_nc = b.cols();
+  octave_idx_type b_nr = b.rows();
+  const double *bvec = b.fortran_vec();
+  Matrix x;
+  info = 0;
+
+  if (nr < 1 || nc < 1 || nr != b_nr)
+    (*current_liboctave_error_handler)
+      ("matrix dimension mismatch in solution of minimum norm problem");
+  else if (nr >= nc)
+    {
+      SparseQR q (a, 2);
+      if (! q.ok ()) 
+	{
+	  info = -1;
+	  return Matrix();
+	}
+      x.resize(nc, b_nc);
+      double *vec = x.fortran_vec();
+      OCTAVE_LOCAL_BUFFER (double, buf, q.S()->m2);
+      for (volatile octave_idx_type i = 0, idx = 0, bidx = 0; i < b_nc; 
+	   i++, idx+=nc, bidx+=b_nr)
+	{
+	  OCTAVE_QUIT;
+	  BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	  // cast away const on bvec, with full knowledge that CSparse 
+	  // won't touch it
+	  CXSPARSE_DNAME (cs_ipvec) (nr, q.S()->Pinv, bvec + bidx, buf);
+	  END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	  for (volatile octave_idx_type j = 0; j < nc; j++)
+	    {
+	      OCTAVE_QUIT;
+	      BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	      CXSPARSE_DNAME (cs_happly) (q.N()->L, j, q.N()->B[j], buf);
+	      END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	    }
+	  BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	  CXSPARSE_DNAME (cs_usolve) (q.N()->U, buf);
+	  CXSPARSE_DNAME (cs_ipvec) (nc, q.S()->Q, buf, vec + idx);
+	  END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	}
+    }
+  else
+    {
+      SparseMatrix at = a.hermitian();
+      SparseQR q (at, 2);
+      if (! q.ok ())
+	{
+	  info = -1;
+	  return Matrix();
+	}
+      x.resize(nc, b_nc);
+      double *vec = x.fortran_vec();
+      OCTAVE_LOCAL_BUFFER (double, buf, nc > q.S()->m2 ? nc : q.S()->m2);
+      for (volatile octave_idx_type i = 0, idx = 0, bidx = 0; i < b_nc; 
+	   i++, idx+=nc, bidx+=b_nr)
+	{
+	  OCTAVE_QUIT;
+	  BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	  // cast away const on bvec, with full knowledge that CSparse 
+	  // won't touch it
+	  CXSPARSE_DNAME (cs_pvec) (nr, q.S()->Q, bvec + bidx, buf);
+	  CXSPARSE_DNAME (cs_utsolve) (q.N()->U, buf);
+	  END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	  for (volatile octave_idx_type j = nr-1; j >= 0; j--)
+	    {
+	      OCTAVE_QUIT;
+	      BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	      CXSPARSE_DNAME (cs_happly) (q.N()->L, j, q.N()->B[j], buf);
+	      END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	    }
+	  BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	  CXSPARSE_DNAME (cs_pvec) (nc, q.S()->Pinv, buf, vec + idx);
+	  END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	}
+    }
+
+  return x;
+#else
+  return Matrix ();
+#endif
+}
+
+SparseMatrix
+qrsolve(const SparseMatrix&a, const SparseMatrix &b, octave_idx_type &info)
+{
+#ifdef HAVE_CXSPARSE
+  octave_idx_type nr = a.rows();
+  octave_idx_type nc = a.cols();
+  octave_idx_type b_nr = b.rows();
+  octave_idx_type b_nc = b.cols();
+  SparseMatrix x;
+  volatile octave_idx_type ii, x_nz;
+  info = 0;
+
+  if (nr < 1 || nc < 1 || nr != b_nr)
+    (*current_liboctave_error_handler)
+      ("matrix dimension mismatch in solution of minimum norm problem");
+  else if (nr >= nc)
+    {
+      SparseQR q (a, 2);
+      if (! q.ok ()) 
+	{
+	  info = -1;
+	  return SparseMatrix();
+	}
+      x = SparseMatrix (nc, b_nc, b.nzmax());
+      x.xcidx(0) = 0;
+      x_nz = b.nzmax();
+      ii = 0;
+      OCTAVE_LOCAL_BUFFER (double, Xx, (b_nr > nc ? b_nr : nc));
+      OCTAVE_LOCAL_BUFFER (double, buf, q.S()->m2);
+      for (volatile octave_idx_type i = 0, idx = 0; i < b_nc; i++, idx+=nc)
+	{
+	  OCTAVE_QUIT;
+	  for (octave_idx_type j = 0; j < b_nr; j++)
+	    Xx[j] = b.xelem(j,i);
+	  BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	  CXSPARSE_DNAME (cs_ipvec) (nr, q.S()->Pinv, Xx, buf);
+	  END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	  for (volatile octave_idx_type j = 0; j < nc; j++)
+	    {
+	      OCTAVE_QUIT;
+	      BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	      CXSPARSE_DNAME (cs_happly) (q.N()->L, j, q.N()->B[j], buf);
+	      END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	    }
+	  BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	  CXSPARSE_DNAME (cs_usolve) (q.N()->U, buf);
+	  CXSPARSE_DNAME (cs_ipvec) (nc, q.S()->Q, buf, Xx);
+	  END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+
+	  for (octave_idx_type j = 0; j < nc; j++)
+	    {
+	      double tmp = Xx[j];
+	      if (tmp != 0.0)
+		{
+		  if (ii == x_nz)
+		    {
+		      // Resize the sparse matrix
+		      octave_idx_type sz = x_nz * (b_nc - i) / b_nc;
+		      sz = (sz > 10 ? sz : 10) + x_nz;
+		      x.change_capacity (sz);
+		      x_nz = sz;
+		    }
+		  x.xdata(ii) = tmp;
+		  x.xridx(ii++) = j;
+		}
+	    }
+	  x.xcidx(i+1) = ii;
+	}
+    }
+  else
+    {
+      SparseMatrix at = a.hermitian();
+      SparseQR q (at, 2);
+      if (! q.ok ())
+	{
+	  info = -1;
+	  return SparseMatrix();
+	}
+      x = SparseMatrix (nc, b_nc, b.nzmax());
+      x.xcidx(0) = 0;
+      x_nz = b.nzmax();
+      ii = 0;
+      OCTAVE_LOCAL_BUFFER (double, Xx, (b_nr > nc ? b_nr : nc));
+      OCTAVE_LOCAL_BUFFER (double, buf, nc > q.S()->m2 ? nc : q.S()->m2);
+      for (volatile octave_idx_type i = 0, idx = 0; i < b_nc; i++, idx+=nc)
+	{
+	  OCTAVE_QUIT;
+	  for (octave_idx_type j = 0; j < b_nr; j++)
+	    Xx[j] = b.xelem(j,i);
+	  BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	  CXSPARSE_DNAME (cs_pvec) (nr, q.S()->Q, Xx, buf);
+	  CXSPARSE_DNAME (cs_utsolve) (q.N()->U, buf);
+	  END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	  for (volatile octave_idx_type j = nr-1; j >= 0; j--)
+	    {
+	      OCTAVE_QUIT;
+	      BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	      CXSPARSE_DNAME (cs_happly) (q.N()->L, j, q.N()->B[j], buf);
+	      END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	    }
+	  BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	  CXSPARSE_DNAME (cs_pvec) (nc, q.S()->Pinv, buf, Xx);
+	  END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+
+	  for (octave_idx_type j = 0; j < nc; j++)
+	    {
+	      double tmp = Xx[j];
+	      if (tmp != 0.0)
+		{
+		  if (ii == x_nz)
+		    {
+		      // Resize the sparse matrix
+		      octave_idx_type sz = x_nz * (b_nc - i) / b_nc;
+		      sz = (sz > 10 ? sz : 10) + x_nz;
+		      x.change_capacity (sz);
+		      x_nz = sz;
+		    }
+		  x.xdata(ii) = tmp;
+		  x.xridx(ii++) = j;
+		}
+	    }
+	  x.xcidx(i+1) = ii;
+	}
+    }
+
+  x.maybe_compress ();
+  return x;
+#else
+  return SparseMatrix ();
+#endif
+}
+
+ComplexMatrix
+qrsolve(const SparseMatrix&a, const ComplexMatrix &b, octave_idx_type &info)
+{
+#ifdef HAVE_CXSPARSE
+  octave_idx_type nr = a.rows();
+  octave_idx_type nc = a.cols();
+  octave_idx_type b_nc = b.cols();
+  octave_idx_type b_nr = b.rows();
+  ComplexMatrix x;
+  info = 0;
+
+  if (nr < 1 || nc < 1 || nr != b_nr)
+    (*current_liboctave_error_handler)
+      ("matrix dimension mismatch in solution of minimum norm problem");
+  else if (nr >= nc)
+    {
+      SparseQR q (a, 2);
+      if (! q.ok ())
+	{
+	  info = -1;
+	  return ComplexMatrix();
+	}
+      x.resize(nc, b_nc);
+      Complex *vec = x.fortran_vec();
+      OCTAVE_LOCAL_BUFFER (double, Xx, (b_nr > nc ? b_nr : nc));
+      OCTAVE_LOCAL_BUFFER (double, Xz, (b_nr > nc ? b_nr : nc));
+      OCTAVE_LOCAL_BUFFER (double, buf, q.S()->m2);
+      for (volatile octave_idx_type i = 0, idx = 0; i < b_nc; i++, idx+=nc)
+	{
+	  OCTAVE_QUIT;
+	  for (octave_idx_type j = 0; j < b_nr; j++)
+	    {
+	      Complex c = b.xelem (j,i);
+	      Xx[j] = std::real (c);
+	      Xz[j] = std::imag (c);
+	    }
+	  BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	  CXSPARSE_DNAME (cs_ipvec) (nr, q.S()->Pinv, Xx, buf);
+	  END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	  for (volatile octave_idx_type j = 0; j < nc; j++)
+	    {
+	      OCTAVE_QUIT;
+	      BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	      CXSPARSE_DNAME (cs_happly) (q.N()->L, j, q.N()->B[j], buf);
+	      END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	    }
+	  BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	  CXSPARSE_DNAME (cs_usolve) (q.N()->U, buf);
+	  CXSPARSE_DNAME (cs_ipvec) (nc, q.S()->Q, buf, Xx);
+
+	  CXSPARSE_DNAME (cs_ipvec) (nr, q.S()->Pinv, Xz, buf);
+	  END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	  for (volatile octave_idx_type j = 0; j < nc; j++)
+	    {
+	      OCTAVE_QUIT;
+	      BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	      CXSPARSE_DNAME (cs_happly) (q.N()->L, j, q.N()->B[j], buf);
+	      END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	    }
+	  BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	  CXSPARSE_DNAME (cs_usolve) (q.N()->U, buf);
+	  CXSPARSE_DNAME (cs_ipvec) (nc, q.S()->Q, buf, Xz);
+	  END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	  for (octave_idx_type j = 0; j < nc; j++)
+	    vec[j+idx] = Complex (Xx[j], Xz[j]);
+	}
+    }
+  else
+    {
+      SparseMatrix at = a.hermitian();
+      SparseQR q (at, 2);
+      if (! q.ok ())
+	{
+	  info = -1;
+	  return ComplexMatrix();
+	}
+      x.resize(nc, b_nc);
+      Complex *vec = x.fortran_vec();
+      OCTAVE_LOCAL_BUFFER (double, Xx, (b_nr > nc ? b_nr : nc));
+      OCTAVE_LOCAL_BUFFER (double, Xz, (b_nr > nc ? b_nr : nc));
+      OCTAVE_LOCAL_BUFFER (double, buf, nc > q.S()->m2 ? nc : q.S()->m2);
+      for (volatile octave_idx_type i = 0, idx = 0; i < b_nc; i++, idx+=nc)
+	{
+	  OCTAVE_QUIT;
+	  for (octave_idx_type j = 0; j < b_nr; j++)
+	    {
+	      Complex c = b.xelem (j,i);
+	      Xx[j] = std::real (c);
+	      Xz[j] = std::imag (c);
+	    }
+	  BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	  CXSPARSE_DNAME (cs_pvec) (nr, q.S()->Q, Xx, buf);
+	  CXSPARSE_DNAME (cs_utsolve) (q.N()->U, buf);
+	  END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	  for (volatile octave_idx_type j = nr-1; j >= 0; j--)
+	    {
+	      OCTAVE_QUIT;
+	      BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	      CXSPARSE_DNAME (cs_happly) (q.N()->L, j, q.N()->B[j], buf);
+	      END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	    }
+	  BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	  CXSPARSE_DNAME (cs_pvec) (nc, q.S()->Pinv, buf, Xx);
+	  CXSPARSE_DNAME (cs_pvec) (nr, q.S()->Q, Xz, buf);
+	  CXSPARSE_DNAME (cs_utsolve) (q.N()->U, buf);
+	  END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	  for (volatile octave_idx_type j = nr-1; j >= 0; j--)
+	    {
+	      OCTAVE_QUIT;
+	      BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	      CXSPARSE_DNAME (cs_happly) (q.N()->L, j, q.N()->B[j], buf);
+	      END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	    }
+	  BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	  CXSPARSE_DNAME (cs_pvec) (nc, q.S()->Pinv, buf, Xz);
+	  END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	  for (octave_idx_type j = 0; j < nc; j++)
+	    vec[j+idx] = Complex (Xx[j], Xz[j]);
+	}
+    }
+
+  return x;
+#else
+  return ComplexMatrix ();
+#endif
+}
+
+SparseComplexMatrix
+qrsolve(const SparseMatrix&a, const SparseComplexMatrix &b, octave_idx_type &info)
+{
+#ifdef HAVE_CXSPARSE
+  octave_idx_type nr = a.rows();
+  octave_idx_type nc = a.cols();
+  octave_idx_type b_nr = b.rows();
+  octave_idx_type b_nc = b.cols();
+  SparseComplexMatrix x;
+  volatile octave_idx_type ii, x_nz;
+  info = 0;
+
+  if (nr < 1 || nc < 1 || nr != b_nr)
+    (*current_liboctave_error_handler)
+      ("matrix dimension mismatch in solution of minimum norm problem");
+  else if (nr >= nc)
+    {
+      SparseQR q (a, 2);
+      if (! q.ok ()) 
+	{
+	  info = -1;
+	  return SparseComplexMatrix();
+	}
+      x = SparseComplexMatrix (nc, b_nc, b.nzmax());
+      x.xcidx(0) = 0;
+      x_nz = b.nzmax();
+      ii = 0;
+      OCTAVE_LOCAL_BUFFER (double, Xx, (b_nr > nc ? b_nr : nc));
+      OCTAVE_LOCAL_BUFFER (double, Xz, (b_nr > nc ? b_nr : nc));
+      OCTAVE_LOCAL_BUFFER (double, buf, q.S()->m2);
+      for (volatile octave_idx_type i = 0, idx = 0; i < b_nc; i++, idx+=nc)
+	{
+	  OCTAVE_QUIT;
+	  for (octave_idx_type j = 0; j < b_nr; j++)
+	    {
+	      Complex c = b.xelem (j,i);
+	      Xx[j] = std::real (c);
+	      Xz[j] = std::imag (c);
+	    }
+	  BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	  CXSPARSE_DNAME (cs_ipvec) (nr, q.S()->Pinv, Xx, buf);
+	  END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	  for (volatile octave_idx_type j = 0; j < nc; j++)
+	    {
+	      OCTAVE_QUIT;
+	      BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	      CXSPARSE_DNAME (cs_happly) (q.N()->L, j, q.N()->B[j], buf);
+	      END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	    }
+	  BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	  CXSPARSE_DNAME (cs_usolve) (q.N()->U, buf);
+	  CXSPARSE_DNAME (cs_ipvec) (nc, q.S()->Q, buf, Xx);
+	  CXSPARSE_DNAME (cs_ipvec) (nr, q.S()->Pinv, Xz, buf);
+	  END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	  for (volatile octave_idx_type j = 0; j < nc; j++)
+	    {
+	      OCTAVE_QUIT;
+	      BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	      CXSPARSE_DNAME (cs_happly) (q.N()->L, j, q.N()->B[j], buf);
+	      END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	    }
+	  BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	  CXSPARSE_DNAME (cs_usolve) (q.N()->U, buf);
+	  CXSPARSE_DNAME (cs_ipvec) (nc, q.S()->Q, buf, Xz);
+	  END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+
+	  for (octave_idx_type j = 0; j < nc; j++)
+	    {
+	      Complex tmp = Complex (Xx[j], Xz[j]);
+	      if (tmp != 0.0)
+		{
+		  if (ii == x_nz)
+		    {
+		      // Resize the sparse matrix
+		      octave_idx_type sz = x_nz * (b_nc - i) / b_nc;
+		      sz = (sz > 10 ? sz : 10) + x_nz;
+		      x.change_capacity (sz);
+		      x_nz = sz;
+		    }
+		  x.xdata(ii) = tmp;
+		  x.xridx(ii++) = j;
+		}
+	    }
+	  x.xcidx(i+1) = ii;
+	}
+    }
+  else
+    {
+      SparseMatrix at = a.hermitian();
+      SparseQR q (at, 2);
+      if (! q.ok ())
+	{
+	  info = -1;
+	  return SparseComplexMatrix();
+	}
+      x = SparseComplexMatrix (nc, b_nc, b.nzmax());
+      x.xcidx(0) = 0;
+      x_nz = b.nzmax();
+      ii = 0;
+      OCTAVE_LOCAL_BUFFER (double, Xx, (b_nr > nc ? b_nr : nc));
+      OCTAVE_LOCAL_BUFFER (double, Xz, (b_nr > nc ? b_nr : nc));
+      OCTAVE_LOCAL_BUFFER (double, buf, nc > q.S()->m2 ? nc : q.S()->m2);
+      for (volatile octave_idx_type i = 0, idx = 0; i < b_nc; i++, idx+=nc)
+	{
+	  OCTAVE_QUIT;
+	  for (octave_idx_type j = 0; j < b_nr; j++)
+	    {
+	      Complex c = b.xelem (j,i);
+	      Xx[j] = std::real (c);
+	      Xz[j] = std::imag (c);
+	    }
+	  BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	  CXSPARSE_DNAME (cs_pvec) (nr, q.S()->Q, Xx, buf);
+	  CXSPARSE_DNAME (cs_utsolve) (q.N()->U, buf);
+	  END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	  for (volatile octave_idx_type j = nr-1; j >= 0; j--)
+	    {
+	      OCTAVE_QUIT;
+	      BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	      CXSPARSE_DNAME (cs_happly) (q.N()->L, j, q.N()->B[j], buf);
+	      END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	    }
+	  BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	  CXSPARSE_DNAME (cs_pvec) (nc, q.S()->Pinv, buf, Xx);
+	  CXSPARSE_DNAME (cs_pvec) (nr, q.S()->Q, Xz, buf);
+	  CXSPARSE_DNAME (cs_utsolve) (q.N()->U, buf);
+	  END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	  for (volatile octave_idx_type j = nr-1; j >= 0; j--)
+	    {
+	      OCTAVE_QUIT;
+	      BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	      CXSPARSE_DNAME (cs_happly) (q.N()->L, j, q.N()->B[j], buf);
+	      END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	    }
+	  BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+	  CXSPARSE_DNAME (cs_pvec) (nc, q.S()->Pinv, buf, Xz);
+	  END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
+
+	  for (octave_idx_type j = 0; j < nc; j++)
+	    {
+	      Complex tmp = Complex (Xx[j], Xz[j]);
+	      if (tmp != 0.0)
+		{
+		  if (ii == x_nz)
+		    {
+		      // Resize the sparse matrix
+		      octave_idx_type sz = x_nz * (b_nc - i) / b_nc;
+		      sz = (sz > 10 ? sz : 10) + x_nz;
+		      x.change_capacity (sz);
+		      x_nz = sz;
+		    }
+		  x.xdata(ii) = tmp;
+		  x.xridx(ii++) = j;
+		}
+	    }
+	  x.xcidx(i+1) = ii;
+	}
+    }
+
+  x.maybe_compress ();
+  return x;
+#else
+  return SparseComplexMatrix ();
+#endif
+}
+
+/*
+;;; Local Variables: ***
+;;; mode: C++ ***
+;;; End: ***
+*/