]> www.ginac.de Git - ginac.git/blobdiff - ginac/matrix.cpp
* Minor optimization: swap instead of assign.
[ginac.git] / ginac / matrix.cpp
index d82abab790356326efc060b7f88749285ad88c49..4c25d12bce11caf2266b9c4c6ccade7a6a37a659 100644 (file)
@@ -3,7 +3,7 @@
  *  Implementation of symbolic matrices */
 
 /*
- *  GiNaC Copyright (C) 1999-2003 Johannes Gutenberg University Mainz, Germany
+ *  GiNaC Copyright (C) 1999-2004 Johannes Gutenberg University Mainz, Germany
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
 #include "lst.h"
 #include "idx.h"
 #include "indexed.h"
+#include "add.h"
 #include "power.h"
 #include "symbol.h"
+#include "operators.h"
 #include "normal.h"
-#include "print.h"
 #include "archive.h"
 #include "utils.h"
 
 namespace GiNaC {
 
-GINAC_IMPLEMENT_REGISTERED_CLASS(matrix, basic)
+GINAC_IMPLEMENT_REGISTERED_CLASS_OPT(matrix, basic,
+  print_func<print_context>(&matrix::do_print).
+  print_func<print_latex>(&matrix::do_print_latex).
+  print_func<print_tree>(&matrix::do_print_tree).
+  print_func<print_python_repr>(&matrix::do_print_python_repr))
 
 //////////
-// default ctor, dtor, copy ctor, assignment operator and helpers:
+// default constructor
 //////////
 
 /** Default ctor.  Initializes to 1 x 1-dimensional zero-matrix. */
-matrix::matrix() : inherited(TINFO_matrix), row(1), col(1)
+matrix::matrix() : inherited(TINFO_matrix), row(1), col(1), m(1, _ex0)
 {
-       m.push_back(_ex0);
+       setflag(status_flags::not_shareable);
 }
 
-void matrix::copy(const matrix & other)
-{
-       inherited::copy(other);
-       row = other.row;
-       col = other.col;
-       m = other.m;  // STL's vector copying invoked here
-}
-
-DEFAULT_DESTROY(matrix)
-
 //////////
-// other ctors
+// other constructors
 //////////
 
 // public
@@ -74,32 +69,36 @@ DEFAULT_DESTROY(matrix)
  *  @param r number of rows
  *  @param c number of cols */
 matrix::matrix(unsigned r, unsigned c)
-  : inherited(TINFO_matrix), row(r), col(c)
+  : inherited(TINFO_matrix), row(r), col(c), m(r*c, _ex0)
 {
-       m.resize(r*c, _ex0);
+       setflag(status_flags::not_shareable);
 }
 
 // protected
 
 /** Ctor from representation, for internal use only. */
 matrix::matrix(unsigned r, unsigned c, const exvector & m2)
-  : inherited(TINFO_matrix), row(r), col(c), m(m2) {}
+  : inherited(TINFO_matrix), row(r), col(c), m(m2)
+{
+       setflag(status_flags::not_shareable);
+}
 
 /** Construct matrix from (flat) list of elements. If the list has fewer
  *  elements than the matrix, the remaining matrix elements are set to zero.
  *  If the list has more elements than the matrix, the excessive elements are
  *  thrown away. */
 matrix::matrix(unsigned r, unsigned c, const lst & l)
-  : inherited(TINFO_matrix), row(r), col(c)
+  : inherited(TINFO_matrix), row(r), col(c), m(r*c, _ex0)
 {
-       m.resize(r*c, _ex0);
+       setflag(status_flags::not_shareable);
 
-       for (unsigned i=0; i<l.nops(); i++) {
-               unsigned x = i % c;
-               unsigned y = i / c;
+       size_t i = 0;
+       for (lst::const_iterator it = l.begin(); it != l.end(); ++it, ++i) {
+               size_t x = i % c;
+               size_t y = i / c;
                if (y >= r)
                        break; // matrix smaller than list: throw away excessive elements
-               m[y*c+x] = l.op(i);
+               m[y*c+x] = *it;
        }
 }
 
@@ -107,8 +106,10 @@ matrix::matrix(unsigned r, unsigned c, const lst & l)
 // archiving
 //////////
 
-matrix::matrix(const archive_node &n, const lst &sym_lst) : inherited(n, sym_lst)
+matrix::matrix(const archive_node &n, lst &sym_lst) : inherited(n, sym_lst)
 {
+       setflag(status_flags::not_shareable);
+
        if (!(n.find_unsigned("row", row)) || !(n.find_unsigned("col", col)))
                throw (std::runtime_error("unknown matrix dimensions in archive"));
        m.reserve(row * col);
@@ -141,74 +142,63 @@ DEFAULT_UNARCHIVE(matrix)
 
 // public
 
-void matrix::print(const print_context & c, unsigned level) const
+void matrix::print_elements(const print_context & c, const char *row_start, const char *row_end, const char *row_sep, const char *col_sep) const
 {
-       if (is_a<print_tree>(c)) {
-
-               inherited::print(c, level);
-
-       } else {
-
-               if (is_a<print_python_repr>(c))
-                       c.s << class_name() << '(';
-
-               if (is_a<print_latex>(c))
-                       c.s << "\\left(\\begin{array}{" << std::string(col,'c') << "}";
-               else
-                       c.s << "[";
-
-               for (unsigned ro=0; ro<row; ++ro) {
-                       if (!is_a<print_latex>(c))
-                               c.s << "[";
-                       for (unsigned co=0; co<col; ++co) {
-                               m[ro*col+co].print(c);
-                               if (co<col-1) {
-                                       if (is_a<print_latex>(c))
-                                               c.s << "&";
-                                       else
-                                               c.s << ",";
-                               } else {
-                                       if (!is_a<print_latex>(c))
-                                               c.s << "]";
-                               }
-                       }
-                       if (ro<row-1) {
-                               if (is_a<print_latex>(c))
-                                       c.s << "\\\\";
-                               else
-                                       c.s << ",";
-                       }
+       for (unsigned ro=0; ro<row; ++ro) {
+               c.s << row_start;
+               for (unsigned co=0; co<col; ++co) {
+                       m[ro*col+co].print(c);
+                       if (co < col-1)
+                               c.s << col_sep;
+                       else
+                               c.s << row_end;
                }
+               if (ro < row-1)
+                       c.s << row_sep;
+       }
+}
 
-               if (is_a<print_latex>(c))
-                       c.s << "\\end{array}\\right)";
-               else
-                       c.s << "]";
+void matrix::do_print(const print_context & c, unsigned level) const
+{
+       c.s << "[";
+       print_elements(c, "[", "]", ",", ",");
+       c.s << "]";
+}
 
-               if (is_a<print_python_repr>(c))
-                       c.s << ')';
+void matrix::do_print_latex(const print_latex & c, unsigned level) const
+{
+       c.s << "\\left(\\begin{array}{" << std::string(col,'c') << "}";
+       print_elements(c, "", "", "\\\\", "&");
+       c.s << "\\end{array}\\right)";
+}
 
-       }
+void matrix::do_print_python_repr(const print_python_repr & c, unsigned level) const
+{
+       c.s << class_name() << '(';
+       print_elements(c, "[", "]", ",", ",");
+       c.s << ')';
 }
 
 /** nops is defined to be rows x columns. */
-unsigned matrix::nops() const
+size_t matrix::nops() const
 {
-       return row*col;
+       return static_cast<size_t>(row) * static_cast<size_t>(col);
 }
 
 /** returns matrix entry at position (i/col, i%col). */
-ex matrix::op(int i) const
+ex matrix::op(size_t i) const
 {
+       GINAC_ASSERT(i<nops());
+       
        return m[i];
 }
 
-/** returns matrix entry at position (i/col, i%col). */
-ex & matrix::let_op(int i)
+/** returns writable matrix entry at position (i/col, i%col). */
+ex & matrix::let_op(size_t i)
 {
-       GINAC_ASSERT(i>=0);
        GINAC_ASSERT(i<nops());
        
+       ensure_if_modifiable();
        return m[i];
 }
 
@@ -234,14 +224,42 @@ ex matrix::eval(int level) const
                                                                                           status_flags::evaluated);
 }
 
-ex matrix::subs(const lst & ls, const lst & lr, bool no_pattern) const
+ex matrix::subs(const exmap & mp, unsigned options) const
 {
        exvector m2(row * col);
        for (unsigned r=0; r<row; ++r)
                for (unsigned c=0; c<col; ++c)
-                       m2[r*col+c] = m[r*col+c].subs(ls, lr, no_pattern);
+                       m2[r*col+c] = m[r*col+c].subs(mp, options);
 
-       return matrix(row, col, m2).basic::subs(ls, lr, no_pattern);
+       return matrix(row, col, m2).subs_one_level(mp, options);
+}
+
+/** Complex conjugate every matrix entry. */
+ex matrix::conjugate() const
+{
+       exvector * ev = 0;
+       for (exvector::const_iterator i=m.begin(); i!=m.end(); ++i) {
+               ex x = i->conjugate();
+               if (ev) {
+                       ev->push_back(x);
+                       continue;
+               }
+               if (are_ex_trivially_equal(x, *i)) {
+                       continue;
+               }
+               ev = new exvector;
+               ev->reserve(m.size());
+               for (exvector::const_iterator j=m.begin(); j!=i; ++j) {
+                       ev->push_back(*j);
+               }
+               ev->push_back(x);
+       }
+       if (ev) {
+               ex result = matrix(row, col, *ev);
+               delete ev;
+               return result;
+       }
+       return *this;
 }
 
 // protected
@@ -367,7 +385,7 @@ ex matrix::add_indexed(const ex & self, const ex & other) const
        GINAC_ASSERT(self.nops() == 2 || self.nops() == 3);
 
        // Only add two matrices
-       if (is_ex_of_type(other.op(0), matrix)) {
+       if (is_a<matrix>(other.op(0))) {
                GINAC_ASSERT(other.nops() == 2 || other.nops() == 3);
 
                const matrix &self_matrix = ex_to<matrix>(self.op(0));
@@ -418,7 +436,7 @@ bool matrix::contract_with(exvector::iterator self, exvector::iterator other, ex
        GINAC_ASSERT(is_a<matrix>(self->op(0)));
 
        // Only contract with other matrices
-       if (!is_ex_of_type(other->op(0), matrix))
+       if (!is_a<matrix>(other->op(0)))
                return false;
 
        GINAC_ASSERT(other->nops() == 2 || other->nops() == 3);
@@ -607,7 +625,7 @@ matrix matrix::pow(const ex & expn) const
        if (col!=row)
                throw (std::logic_error("matrix::pow(): matrix not square"));
        
-       if (is_ex_exactly_of_type(expn, numeric)) {
+       if (is_exactly_a<numeric>(expn)) {
                // Integer cases are computed by successive multiplication, using the
                // obvious shortcut of storing temporaries, like A^4 == (A*A)*(A*A).
                if (expn.info(info_flags::integer)) {
@@ -675,7 +693,7 @@ ex & matrix::operator() (unsigned ro, unsigned co)
 
 /** Transposed of an m x n matrix, producing a new n x m matrix object that
  *  represents the transposed. */
-matrix matrix::transpose(void) const
+matrix matrix::transpose() const
 {
        exvector trans(this->cols()*this->rows());
        
@@ -712,7 +730,7 @@ ex matrix::determinant(unsigned algo) const
        unsigned sparse_count = 0;  // counts non-zero elements
        exvector::const_iterator r = m.begin(), rend = m.end();
        while (r != rend) {
-               lst srl;  // symbol replacement list
+               exmap srl;  // symbol replacement list
                ex rtest = r->to_rational(srl);
                if (!rtest.is_zero())
                        ++sparse_count;
@@ -746,7 +764,7 @@ ex matrix::determinant(unsigned algo) const
                else
                        return m[0].expand();
        }
-       
+
        // Compute the determinant
        switch(algo) {
                case determinant_algo::gauss: {
@@ -832,7 +850,7 @@ ex matrix::determinant(unsigned algo) const
  *
  *  @return    the sum of diagonal elements
  *  @exception logic_error (matrix not square) */
-ex matrix::trace(void) const
+ex matrix::trace() const
 {
        if (row != col)
                throw (std::logic_error("matrix::trace(): matrix not square"));
@@ -842,7 +860,7 @@ ex matrix::trace(void) const
                tr += m[r*col+r];
        
        if (tr.info(info_flags::rational_function) &&
-               !tr.info(info_flags::crational_polynomial))
+          !tr.info(info_flags::crational_polynomial))
                return tr.normal();
        else
                return tr.expand();
@@ -860,7 +878,7 @@ ex matrix::trace(void) const
  *  @return    characteristic polynomial as new expression
  *  @exception logic_error (matrix not square)
  *  @see       matrix::determinant() */
-ex matrix::charpoly(const symbol & lambda) const
+ex matrix::charpoly(const ex & lambda) const
 {
        if (row != col)
                throw (std::logic_error("matrix::charpoly(): matrix not square"));
@@ -877,27 +895,30 @@ ex matrix::charpoly(const symbol & lambda) const
        // trapped and we use Leverrier's algorithm which goes as row^3 for
        // every coefficient.  The expensive part is the matrix multiplication.
        if (numeric_flag) {
+
                matrix B(*this);
                ex c = B.trace();
-               ex poly = power(lambda,row)-c*power(lambda,row-1);
+               ex poly = power(lambda, row) - c*power(lambda, row-1);
                for (unsigned i=1; i<row; ++i) {
                        for (unsigned j=0; j<row; ++j)
                                B.m[j*col+j] -= c;
                        B = this->mul(B);
-                       c = B.trace()/ex(i+1);
-                       poly -= c*power(lambda,row-i-1);
+                       c = B.trace() / ex(i+1);
+                       poly -= c*power(lambda, row-i-1);
                }
                if (row%2)
                        return -poly;
                else
                        return poly;
-       }
+
+       } else {
        
-       matrix M(*this);
-       for (unsigned r=0; r<col; ++r)
-               M.m[r*col+r] -= lambda;
+               matrix M(*this);
+               for (unsigned r=0; r<col; ++r)
+                       M.m[r*col+r] -= lambda;
        
-       return M.determinant().collect(lambda);
+               return M.determinant().collect(lambda);
+       }
 }
 
 
@@ -906,7 +927,7 @@ ex matrix::charpoly(const symbol & lambda) const
  *  @return    the inverted matrix
  *  @exception logic_error (matrix not square)
  *  @exception runtime_error (singular matrix) */
-matrix matrix::inverse(void) const
+matrix matrix::inverse() const
 {
        if (row != col)
                throw (std::logic_error("matrix::inverse(): matrix not square"));
@@ -945,14 +966,15 @@ matrix matrix::inverse(void) const
  *
  *  @param vars n x p matrix, all elements must be symbols 
  *  @param rhs m x p matrix
+ *  @param algo selects the solving algorithm
  *  @return n x p solution matrix
  *  @exception logic_error (incompatible matrices)
  *  @exception invalid_argument (1st argument must be matrix of symbols)
  *  @exception runtime_error (inconsistent linear system)
  *  @see       solve_algo */
 matrix matrix::solve(const matrix & vars,
-                                        const matrix & rhs,
-                                        unsigned algo) const
+                     const matrix & rhs,
+                     unsigned algo) const
 {
        const unsigned m = this->rows();
        const unsigned n = this->cols();
@@ -1045,6 +1067,29 @@ matrix matrix::solve(const matrix & vars,
 }
 
 
+/** Compute the rank of this matrix. */
+unsigned matrix::rank() const
+{
+       // Method:
+       // Transform this matrix into upper echelon form and then count the
+       // number of non-zero rows.
+
+       GINAC_ASSERT(row*col==m.capacity());
+
+       // Actually, any elimination scheme will do since we are only
+       // interested in the echelon matrix' zeros.
+       matrix to_eliminate = *this;
+       to_eliminate.fraction_free_elimination();
+
+       unsigned r = row*col;  // index of last non-zero element
+       while (r--) {
+               if (!to_eliminate.m[r].is_zero())
+                       return 1+r/col;
+       }
+       return 0;
+}
+
+
 // protected
 
 /** Recursive determinant for small matrices having at least one symbolic
@@ -1057,7 +1102,7 @@ matrix matrix::solve(const matrix & vars,
  *
  *  @return the determinant as a new expression (in expanded form)
  *  @see matrix::determinant() */
-ex matrix::determinant_minor(void) const
+ex matrix::determinant_minor() const
 {
        // for small matrices the algorithm does not make any sense:
        const unsigned n = this->cols();
@@ -1160,7 +1205,7 @@ ex matrix::determinant_minor(void) const
                                        Pkey[j] = Pkey[j-1]+1;
                } while(fc);
                // next column, so change the role of A and B:
-               A = B;
+               A.swap(B);
                B.clear();
        }
        
@@ -1186,8 +1231,8 @@ int matrix::gauss_elimination(const bool det)
        int sign = 1;
        
        unsigned r0 = 0;
-       for (unsigned r1=0; (r1<n-1)&&(r0<m-1); ++r1) {
-               int indx = pivot(r0, r1, true);
+       for (unsigned c0=0; c0<n && r0<m-1; ++c0) {
+               int indx = pivot(r0, c0, true);
                if (indx == -1) {
                        sign = 0;
                        if (det)
@@ -1197,17 +1242,17 @@ int matrix::gauss_elimination(const bool det)
                        if (indx > 0)
                                sign = -sign;
                        for (unsigned r2=r0+1; r2<m; ++r2) {
-                               if (!this->m[r2*n+r1].is_zero()) {
+                               if (!this->m[r2*n+c0].is_zero()) {
                                        // yes, there is something to do in this row
-                                       ex piv = this->m[r2*n+r1] / this->m[r0*n+r1];
-                                       for (unsigned c=r1+1; c<n; ++c) {
+                                       ex piv = this->m[r2*n+c0] / this->m[r0*n+c0];
+                                       for (unsigned c=c0+1; c<n; ++c) {
                                                this->m[r2*n+c] -= piv * this->m[r0*n+c];
                                                if (!this->m[r2*n+c].info(info_flags::numeric))
                                                        this->m[r2*n+c] = this->m[r2*n+c].normal();
                                        }
                                }
                                // fill up left hand side with zeros
-                               for (unsigned c=0; c<=r1; ++c)
+                               for (unsigned c=r0; c<=c0; ++c)
                                        this->m[r2*n+c] = _ex0;
                        }
                        if (det) {
@@ -1218,7 +1263,12 @@ int matrix::gauss_elimination(const bool det)
                        ++r0;
                }
        }
-       
+       // clear remaining rows
+       for (unsigned r=r0+1; r<m; ++r) {
+               for (unsigned c=0; c<n; ++c)
+                       this->m[r*n+c] = _ex0;
+       }
+
        return sign;
 }
 
@@ -1240,8 +1290,8 @@ int matrix::division_free_elimination(const bool det)
        int sign = 1;
        
        unsigned r0 = 0;
-       for (unsigned r1=0; (r1<n-1)&&(r0<m-1); ++r1) {
-               int indx = pivot(r0, r1, true);
+       for (unsigned c0=0; c0<n && r0<m-1; ++c0) {
+               int indx = pivot(r0, c0, true);
                if (indx==-1) {
                        sign = 0;
                        if (det)
@@ -1251,10 +1301,10 @@ int matrix::division_free_elimination(const bool det)
                        if (indx>0)
                                sign = -sign;
                        for (unsigned r2=r0+1; r2<m; ++r2) {
-                               for (unsigned c=r1+1; c<n; ++c)
-                                       this->m[r2*n+c] = (this->m[r0*n+r1]*this->m[r2*n+c] - this->m[r2*n+r1]*this->m[r0*n+c]).expand();
+                               for (unsigned c=c0+1; c<n; ++c)
+                                       this->m[r2*n+c] = (this->m[r0*n+c0]*this->m[r2*n+c] - this->m[r2*n+c0]*this->m[r0*n+c]).expand();
                                // fill up left hand side with zeros
-                               for (unsigned c=0; c<=r1; ++c)
+                               for (unsigned c=r0; c<=c0; ++c)
                                        this->m[r2*n+c] = _ex0;
                        }
                        if (det) {
@@ -1265,7 +1315,12 @@ int matrix::division_free_elimination(const bool det)
                        ++r0;
                }
        }
-       
+       // clear remaining rows
+       for (unsigned r=r0+1; r<m; ++r) {
+               for (unsigned c=0; c<n; ++c)
+                       this->m[r*n+c] = _ex0;
+       }
+
        return sign;
 }
 
@@ -1290,7 +1345,7 @@ int matrix::fraction_free_elimination(const bool det)
        //
        // Bareiss (fraction-free) elimination in addition divides that element
        // by m[k-1](k-1,k-1) for k>1, where it can be shown by means of the
-       // Sylvester determinant that this really divides m[k+1](r,c).
+       // Sylvester identity that this really divides m[k+1](r,c).
        //
        // We also allow rational functions where the original prove still holds.
        // However, we must care for numerator and denominator separately and
@@ -1327,7 +1382,7 @@ int matrix::fraction_free_elimination(const bool det)
        // makes things more complicated than they need to be.
        matrix tmp_n(*this);
        matrix tmp_d(m,n);  // for denominators, if needed
-       lst srl;  // symbol replacement list
+       exmap srl;  // symbol replacement list
        exvector::const_iterator cit = this->m.begin(), citend = this->m.end();
        exvector::iterator tmp_n_it = tmp_n.m.begin(), tmp_d_it = tmp_d.m.begin();
        while (cit != citend) {
@@ -1338,8 +1393,8 @@ int matrix::fraction_free_elimination(const bool det)
        }
        
        unsigned r0 = 0;
-       for (unsigned r1=0; (r1<n-1)&&(r0<m-1); ++r1) {
-               int indx = tmp_n.pivot(r0, r1, true);
+       for (unsigned c0=0; c0<n && r0<m-1; ++c0) {
+               int indx = tmp_n.pivot(r0, c0, true);
                if (indx==-1) {
                        sign = 0;
                        if (det)
@@ -1349,17 +1404,17 @@ int matrix::fraction_free_elimination(const bool det)
                        if (indx>0) {
                                sign = -sign;
                                // tmp_n's rows r0 and indx were swapped, do the same in tmp_d:
-                               for (unsigned c=r1; c<n; ++c)
+                               for (unsigned c=c0; c<n; ++c)
                                        tmp_d.m[n*indx+c].swap(tmp_d.m[n*r0+c]);
                        }
                        for (unsigned r2=r0+1; r2<m; ++r2) {
-                               for (unsigned c=r1+1; c<n; ++c) {
-                                       dividend_n = (tmp_n.m[r0*n+r1]*tmp_n.m[r2*n+c]*
-                                                     tmp_d.m[r2*n+r1]*tmp_d.m[r0*n+c]
-                                                    -tmp_n.m[r2*n+r1]*tmp_n.m[r0*n+c]*
-                                                     tmp_d.m[r0*n+r1]*tmp_d.m[r2*n+c]).expand();
-                                       dividend_d = (tmp_d.m[r2*n+r1]*tmp_d.m[r0*n+c]*
-                                                     tmp_d.m[r0*n+r1]*tmp_d.m[r2*n+c]).expand();
+                               for (unsigned c=c0+1; c<n; ++c) {
+                                       dividend_n = (tmp_n.m[r0*n+c0]*tmp_n.m[r2*n+c]*
+                                                     tmp_d.m[r2*n+c0]*tmp_d.m[r0*n+c]
+                                                    -tmp_n.m[r2*n+c0]*tmp_n.m[r0*n+c]*
+                                                     tmp_d.m[r0*n+c0]*tmp_d.m[r2*n+c]).expand();
+                                       dividend_d = (tmp_d.m[r2*n+c0]*tmp_d.m[r0*n+c]*
+                                                     tmp_d.m[r0*n+c0]*tmp_d.m[r2*n+c]).expand();
                                        bool check = divide(dividend_n, divisor_n,
                                                            tmp_n.m[r2*n+c], true);
                                        check &= divide(dividend_d, divisor_d,
@@ -1367,13 +1422,13 @@ int matrix::fraction_free_elimination(const bool det)
                                        GINAC_ASSERT(check);
                                }
                                // fill up left hand side with zeros
-                               for (unsigned c=0; c<=r1; ++c)
+                               for (unsigned c=r0; c<=c0; ++c)
                                        tmp_n.m[r2*n+c] = _ex0;
                        }
-                       if ((r1<n-1)&&(r0<m-1)) {
+                       if (c0<n && r0<m-1) {
                                // compute next iteration's divisor
-                               divisor_n = tmp_n.m[r0*n+r1].expand();
-                               divisor_d = tmp_d.m[r0*n+r1].expand();
+                               divisor_n = tmp_n.m[r0*n+c0].expand();
+                               divisor_d = tmp_d.m[r0*n+c0].expand();
                                if (det) {
                                        // save space by deleting no longer needed elements
                                        for (unsigned c=0; c<n; ++c) {
@@ -1385,12 +1440,18 @@ int matrix::fraction_free_elimination(const bool det)
                        ++r0;
                }
        }
+       // clear remaining rows
+       for (unsigned r=r0+1; r<m; ++r) {
+               for (unsigned c=0; c<n; ++c)
+                       tmp_n.m[r*n+c] = _ex0;
+       }
+
        // repopulate *this matrix:
        exvector::iterator it = this->m.begin(), itend = this->m.end();
        tmp_n_it = tmp_n.m.begin();
        tmp_d_it = tmp_d.m.begin();
        while (it != itend)
-               *it++ = ((*tmp_n_it++)/(*tmp_d_it++)).subs(srl);
+               *it++ = ((*tmp_n_it++)/(*tmp_d_it++)).subs(srl, subs_options::no_pattern);
        
        return sign;
 }
@@ -1449,34 +1510,45 @@ int matrix::pivot(unsigned ro, unsigned co, bool symbolic)
 
 ex lst_to_matrix(const lst & l)
 {
+       lst::const_iterator itr, itc;
+
        // Find number of rows and columns
-       unsigned rows = l.nops(), cols = 0, i, j;
-       for (i=0; i<rows; i++)
-               if (l.op(i).nops() > cols)
-                       cols = l.op(i).nops();
+       size_t rows = l.nops(), cols = 0;
+       for (itr = l.begin(); itr != l.end(); ++itr) {
+               if (!is_a<lst>(*itr))
+                       throw (std::invalid_argument("lst_to_matrix: argument must be a list of lists"));
+               if (itr->nops() > cols)
+                       cols = itr->nops();
+       }
 
        // Allocate and fill matrix
        matrix &M = *new matrix(rows, cols);
        M.setflag(status_flags::dynallocated);
-       for (i=0; i<rows; i++)
-               for (j=0; j<cols; j++)
-                       if (l.op(i).nops() > j)
-                               M(i, j) = l.op(i).op(j);
-                       else
-                               M(i, j) = _ex0;
+
+       unsigned i;
+       for (itr = l.begin(), i = 0; itr != l.end(); ++itr, ++i) {
+               unsigned j;
+               for (itc = ex_to<lst>(*itr).begin(), j = 0; itc != ex_to<lst>(*itr).end(); ++itc, ++j)
+                       M(i, j) = *itc;
+       }
+
        return M;
 }
 
 ex diag_matrix(const lst & l)
 {
-       unsigned dim = l.nops();
+       lst::const_iterator it;
+       size_t dim = l.nops();
 
-       matrix &m = *new matrix(dim, dim);
-       m.setflag(status_flags::dynallocated);
-       for (unsigned i=0; i<dim; i++)
-               m(i, i) = l.op(i);
+       // Allocate and fill matrix
+       matrix &M = *new matrix(dim, dim);
+       M.setflag(status_flags::dynallocated);
 
-       return m;
+       unsigned i;
+       for (it = l.begin(), i = 0; it != l.end(); ++it, ++i)
+               M(i, i) = *it;
+
+       return M;
 }
 
 ex unit_matrix(unsigned r, unsigned c)