cloog-0.16.3/source/matrix/constraintset.c

   /**-------------------------------------------------------------------**
    **                               CLooG                               **
    **-------------------------------------------------------------------**
    **                          constraintset.c                          **
    **-------------------------------------------------------------------**
    **                    First version: april 17th 2005                 **
    **-------------------------------------------------------------------**/


/******************************************************************************
 *               CLooG : the Chunky Loop Generator (experimental)             *
 ******************************************************************************
 *                                                                            *
 * Copyright (C) 2005 Cedric Bastoul                                          *
 *                                                                            *
 * This library is free software; you can redistribute it and/or              *
 * modify it under the terms of the GNU Lesser General Public                 *
 * License as published by the Free Software Foundation; either               *
 * version 2.1 of the License, or (at your option) any later version.         *
 *                                                                            *
 * This library 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          *
 * Lesser General Public License for more details.                            *
 *                                                                            *
 * You should have received a copy of the GNU Lesser General Public           *
 * License along with this library; if not, write to the Free Software        *
 * Foundation, Inc., 51 Franklin Street, Fifth Floor,                         *
 * Boston, MA  02110-1301  USA                                                *
 *                                                                            *
 * CLooG, the Chunky Loop Generator                                           *
 * Written by Cedric Bastoul, Cedric.Bastoul@inria.fr                         *
 *                                                                            *
 ******************************************************************************/
/* CAUTION: the english used for comments is probably the worst you ever read,
 *          please feel free to correct and improve it !
 */


# include <stdlib.h>
# include <stdio.h>
# include <ctype.h>
#include <cloog/cloog.h>
#include <cloog/matrix/constraintset.h>


#define ALLOC(type) (type*)malloc(sizeof(type))
#define ALLOCN(type,n) (type*)malloc((n)*sizeof(type))


CloogConstraint *cloog_constraint_first(CloogConstraintSet *constraints);
CloogConstraint *cloog_constraint_next(CloogConstraint *constraint);


CloogConstraintSet *cloog_constraint_set_from_cloog_matrix(CloogMatrix *M)
{
	return (CloogConstraintSet *)M;
}


void cloog_constraint_set_free(CloogConstraintSet *constraints)
{
	cloog_matrix_free(&constraints->M);
}

int cloog_constraint_set_contains_level(CloogConstraintSet *constraints,
			int level, int nb_parameters)
{
	return constraints->M.NbColumns - 2 - nb_parameters >= level;
}

/* Check if the variable at position level is defined by an
 * equality.  If so, return the row number.  Otherwise, return -1.
 *
 * If there is an equality, we can print it directly -no ambiguity-.
 * PolyLib can give more than one equality, we use just the first one
 * (this is a PolyLib problem, but all equalities are equivalent).
 */
CloogConstraint *cloog_constraint_set_defining_equality(CloogConstraintSet *constraints, int level)
{
	CloogConstraint *constraint = ALLOC(CloogConstraint);
	int i;

	constraint->set = constraints;
	for (i = 0; i < constraints->M.NbRows; i++)
		if (cloog_int_is_zero(constraints->M.p[i][0]) &&
		    !cloog_int_is_zero(constraints->M.p[i][level])) {
			constraint->line = &constraints->M.p[i];
			return constraint;
		    }
	free(constraint);
	return cloog_constraint_invalid();
}

/* Check if the variable (e) at position level is defined by a
 * pair of inequalities
 *		 <a, i> + -m e +  <b, p> + k1 >= 0
 *		<-a, i> +  m e + <-b, p> + k2 >= 0
 * with 0 <= k1 + k2 < m
 * If so return the row number of the upper bound and set *lower
 * to the row number of the lower bound.  If not, return -1.
 *
 * If the variable at position level occurs in any other constraint,
 * then we currently return -1.  The modulo guard that we would generate
 * would still be correct, but we would also need to generate
 * guards corresponding to the other constraints, and this has not
 * been implemented yet.
 */
CloogConstraint *cloog_constraint_set_defining_inequalities(CloogConstraintSet *constraints,
	int level, CloogConstraint **lower, int nb_par)
{
	int i, j, k;
	cloog_int_t m;
	CloogMatrix *matrix = &constraints->M;
	unsigned len = matrix->NbColumns - 2;
	unsigned nb_iter = len - nb_par;
	CloogConstraint *constraint;

	for (i = 0; i < matrix->NbRows; i++) {
		if (cloog_int_is_zero(matrix->p[i][level]))
			continue;
		if (cloog_int_is_zero(matrix->p[i][0]))
			return cloog_constraint_invalid();
		if (cloog_int_is_one(matrix->p[i][level]))
			return cloog_constraint_invalid();
		if (cloog_int_is_neg_one(matrix->p[i][level]))
			return cloog_constraint_invalid();
		if (cloog_seq_first_non_zero(matrix->p[i]+level+1,
				    (1+nb_iter)-(level+1)) != -1)
			return cloog_constraint_invalid();
		for (j = i+1; j < matrix->NbRows; ++j) {
			if (cloog_int_is_zero(matrix->p[j][level]))
				continue;
			if (cloog_int_is_zero(matrix->p[j][0]))
				return cloog_constraint_invalid();
			if (cloog_int_is_one(matrix->p[j][level]))
				return cloog_constraint_invalid();
			if (cloog_int_is_neg_one(matrix->p[j][level]))
				return cloog_constraint_invalid();
			if (cloog_seq_first_non_zero(matrix->p[j]+level+1,
					    (1+nb_iter)-(level+1)) != -1)
				return cloog_constraint_invalid();

			cloog_int_init(m);
			cloog_int_add(m, matrix->p[i][1+len], matrix->p[j][1+len]);
			if (cloog_int_is_neg(m) ||
			    cloog_int_abs_ge(m, matrix->p[i][level])) {
				cloog_int_clear(m);
				return cloog_constraint_invalid();
			}
			cloog_int_clear(m);

			if (!cloog_seq_is_neg(matrix->p[i]+1, matrix->p[j]+1,
						len))
				return cloog_constraint_invalid();
			for (k = j+1; k < matrix->NbRows; ++k)
				if (!cloog_int_is_zero(matrix->p[k][level]))
					return cloog_constraint_invalid();
			*lower = ALLOC(CloogConstraint);
			constraint = ALLOC(CloogConstraint);
			(*lower)->set = constraints;
			constraint->set = constraints;
			if (cloog_int_is_pos(matrix->p[i][level])) {
				(*lower)->line = &matrix->p[i];
				constraint->line = &matrix->p[j];
			} else {
				(*lower)->line = &matrix->p[j];
				constraint->line = &matrix->p[i];
			}
			return constraint;
		}
	}
	return cloog_constraint_invalid();
}

int cloog_constraint_set_total_dimension(CloogConstraintSet *constraints)
{
	return constraints->M.NbColumns - 2;
}

int cloog_constraint_set_n_iterators(CloogConstraintSet *constraint, int nb_par)
{
	return cloog_constraint_set_total_dimension(constraint) - nb_par;
}

int cloog_equal_total_dimension(CloogEqualities *equal)
{
	return cloog_constraint_set_total_dimension(equal->constraints);
}

int cloog_constraint_total_dimension(CloogConstraint *constraint)
{
	return cloog_constraint_set_total_dimension(constraint->set);
}



/******************************************************************************
 *                        Equalities spreading functions                      *
 ******************************************************************************/


/* Equalities are stored inside a CloogMatrix data structure called "equal".
 * This matrix has (nb_scattering + nb_iterators + 1) rows (i.e. total
 * dimensions + 1, the "+ 1" is because a statement can be included inside an
 * external loop without iteration domain), and (nb_scattering + nb_iterators +
 * nb_parameters + 2) columns (all unknowns plus the scalar plus the equality
 * type). The ith row corresponds to the equality "= 0" for the ith dimension
 * iterator. The first column gives the equality type (0: no equality, then
 * EQTYPE_* -see pprint.h-). At each recursion of pprint, if an equality for
 * the current level is found, the corresponding row is updated. Then the
 * equality if it exists is used to simplify expressions (e.g. if we have 
 * "i+1" while we know that "i=2", we simplify it in "3"). At the end of
 * the pprint call, the corresponding row is reset to zero.
 */

CloogEqualities *cloog_equal_alloc(int n, int nb_levels,
			int nb_parameters)
{
    int i;
    CloogEqualities *equal = ALLOC(CloogEqualities);

    equal->constraints = cloog_constraint_set_from_cloog_matrix(
		cloog_matrix_alloc(n, nb_levels + nb_parameters + 1));
    equal->types = ALLOCN(int, n);
    for (i = 0; i < n; ++i)
	equal->types[i] = EQTYPE_NONE;
    return equal;
}

void cloog_equal_free(CloogEqualities *equal)
{
    cloog_matrix_free(&equal->constraints->M);
    free(equal->types);
    free(equal);
}

int cloog_equal_count(CloogEqualities *equal)
{
    return equal->constraints->M.NbRows;
}

CloogConstraintSet *cloog_equal_constraints(CloogEqualities *equal)
{
    return equal->constraints;
}


/**
 * cloog_constraint_equal_type function :
 * This function returns the type of the equality in the constraint (line) of
 * (constraints) for the element (level). An equality is 'constant' iff all
 * other factors are null except the constant one. It is a 'pure item' iff
 * it is equal or opposite to a single variable or parameter.
 * Otherwise it is an 'affine expression'.
 * For instance:
 *   i = -13 is constant, i = j, j = -M are pure items,
 *   j = 2*M, i = j+1, 2*j = M are affine expressions.
 *
 * - constraints is the matrix of constraints,
 * - level is the column number in equal of the element which is 'equal to',
 **
 * - July     3rd 2002: first version, called pprint_equal_isconstant. 
 * - July     6th 2002: adaptation for the 3 types. 
 * - June    15th 2005: (debug) expr = domain->Constraint[line] was evaluated
 *                      before checking if line != ONE_TIME_LOOP. Since
 *                      ONE_TIME_LOOP is -1, an invalid read was possible.
 * - October 19th 2005: Removal of the once-time-loop specific processing.
 */
static int cloog_constraint_equal_type(CloogConstraint *constraint, int level)
{ 
  int i, one=0 ;
  cloog_int_t *expr;
    
  expr = *constraint->line;
  
  if (!cloog_int_is_one(expr[level]) && !cloog_int_is_neg_one(expr[level]))
    return EQTYPE_EXAFFINE;

  /* There is only one non null factor, and it must be +1 or -1 for
   * iterators or parameters.
   */ 
  for (i = 1;i <= constraint->set->M.NbColumns-2; i++)
  if (!cloog_int_is_zero(expr[i]) && (i != level)) {
    if ((!cloog_int_is_one(expr[i]) && !cloog_int_is_neg_one(expr[i])) || (one != 0))
    return EQTYPE_EXAFFINE ;
    else
    one = 1 ;
  }
  /* if the constant factor is non null, it must be alone. */
  if (one != 0) {
    if (!cloog_int_is_zero(expr[constraint->set->M.NbColumns-1]))
    return EQTYPE_EXAFFINE ;
  }
  else
  return EQTYPE_CONSTANT ;
  
  return EQTYPE_PUREITEM ;
}


int cloog_equal_type(CloogEqualities *equal, int level)
{
	return equal->types[level-1];
}


/**
 * cloog_equal_update function:
 * this function updates a matrix of equalities where each row corresponds to
 * the equality "=0" of an affine expression such that the entry at column
 * "row" (="level") is not zero. This matrix is upper-triangular, except the
 * row number "level-1" which has to be updated for the matrix to be triangular.
 * This function achieves the processing.
 * - equal is the matrix to be updated,
 * - level gives the row that has to be updated (it is actually row "level-1"),
 * - nb_par is the number of parameters of the program.
 **
 * - September 20th 2005: first version.
 */
static void cloog_equal_update(CloogEqualities *equal, int level, int nb_par)
{ int i, j ;
  cloog_int_t gcd, factor_level, factor_outer, temp_level, temp_outer;
  
  cloog_int_init(gcd);
  cloog_int_init(temp_level);
  cloog_int_init(temp_outer);
  cloog_int_init(factor_level);
  cloog_int_init(factor_outer);
  
  /* For each previous level, */
  for (i=level-2;i>=0;i--)
  { /* if the corresponding iterator is inside the current equality and is equal
     * to something,
     */
    if (!cloog_int_is_zero(equal->constraints->M.p[level-1][i+1]) && equal->types[i])
    { /* Compute the Greatest Common Divisor. */ 
      cloog_int_gcd(gcd, equal->constraints->M.p[level-1][i+1],
			 equal->constraints->M.p[i][i+1]);
      
      /* Compute the factors to apply to each row vector element. */
      cloog_int_divexact(factor_level, equal->constraints->M.p[i][i+1], gcd);
      cloog_int_divexact(factor_outer, equal->constraints->M.p[level-1][i+1], gcd);
            
      /* Now update the row 'level'. */
      /* - the iterators, up to level, */
      for (j = 1; j <= level; j++) {
        cloog_int_mul(temp_level, factor_level,
			equal->constraints->M.p[level-1][j]);
        cloog_int_mul(temp_outer, factor_outer, equal->constraints->M.p[i][j]);
        cloog_int_sub(equal->constraints->M.p[level-1][j], temp_level, temp_outer);
      }
      /* - between last useful iterator (level) and the first parameter, the
       *   matrix is sparse (full of zeroes), we just do nothing there. 
       * - the parameters and the scalar.
       */
      for (j = 0; j < nb_par + 1; j++) {
        cloog_int_mul(temp_level,factor_level,
                       equal->constraints->M.p[level-1]
					[equal->constraints->M.NbColumns-j-1]);
        cloog_int_mul(temp_outer,factor_outer,
                       equal->constraints->M.p[i][equal->constraints->M.NbColumns-j-1]);
        cloog_int_sub(equal->constraints->M.p[level-1]
					 [equal->constraints->M.NbColumns-j-1],
	               temp_level,temp_outer) ;
      }
    }
  }
  
  /* Normalize (divide by GCD of all elements) the updated equality. */
  cloog_seq_normalize(&(equal->constraints->M.p[level-1][1]),
			equal->constraints->M.NbColumns-1);

  cloog_int_clear(gcd);
  cloog_int_clear(temp_level);
  cloog_int_clear(temp_outer);
  cloog_int_clear(factor_level);
  cloog_int_clear(factor_outer);
}


/**
 * cloog_equal_add function:
 * This function updates the row (level-1) of the equality matrix (equal) with
 * the row that corresponds to the row (line) of the matrix (matrix).
 * - equal is the matrix of equalities,
 * - matrix is the matrix of constraints,
 * - level is the column number in matrix of the element which is 'equal to',
 * - line is the line number in matrix of the constraint we want to study,
 * - the infos structure gives the user all options on code printing and more.
 **
 * - July     2nd 2002: first version. 
 * - October 19th 2005: Addition of the once-time-loop specific processing.
 */
void cloog_equal_add(CloogEqualities *equal, CloogConstraintSet *constraints,
			int level, CloogConstraint *line, int nb_par)
{ 
  int j;
  CloogConstraint *i = cloog_constraint_invalid();
  CloogMatrix *matrix = &constraints->M;

  /* If we are in the case of a loop running once, this means that the equality
   * comes from an inequality. Here we find this inequality.
   */
  if (!cloog_constraint_is_valid(line))
  { for (i = cloog_constraint_first(constraints);
	 cloog_constraint_is_valid(i); i = cloog_constraint_next(i))
    if ((!cloog_int_is_zero(i->line[0][0]))&& (!cloog_int_is_zero(i->line[0][level])))
    { line = i ;
      
      /* Since in once-time-loops, equalities derive from inequalities, we
       * may have to offset the values. For instance if we have 2i>=3, the
       * equality is in fact i=2. This may happen when the level coefficient is
       * not 1 or -1 and the scalar value is not zero. In any other case (e.g.,
       * if the inequality is an expression including outer loop counters or
       * parameters) the once time loop would not have been detected
       * because of floord and ceild functions.
       */
      if (cloog_int_ne_si(i->line[0][level],1) &&
          cloog_int_ne_si(i->line[0][level],-1) &&
	  !cloog_int_is_zero(i->line[0][matrix->NbColumns-1])) {
	cloog_int_t denominator;
        
	cloog_int_init(denominator);
	cloog_int_abs(denominator, i->line[0][level]);
	cloog_int_fdiv_q(i->line[0][matrix->NbColumns-1],
			 i->line[0][matrix->NbColumns-1], denominator);
	cloog_int_set_si(i->line[0][level], cloog_int_sgn(i->line[0][level]));
	cloog_int_clear(denominator);
      }
            
      break ;
    }
  }
  assert(cloog_constraint_is_valid(line));
  
  /* We update the line of equal corresponding to level:
   * - the first element gives the equality type,
   */
  equal->types[level-1] = cloog_constraint_equal_type(line, level);
  /* - the other elements corresponding to the equality itself
   *   (the iterators up to level, then the parameters and the scalar).
   */
  for (j=1;j<=level;j++)
      cloog_int_set(equal->constraints->M.p[level-1][j], line->line[0][j]);
  for (j = 0; j < nb_par + 1; j++)
      cloog_int_set(equal->constraints->M.p[level-1][equal->constraints->M.NbColumns-j-1],
		   line->line[0][line->set->M.NbColumns-j-1]);
  
  if (cloog_constraint_is_valid(i))
    cloog_constraint_release(line);
  cloog_equal_update(equal, level, nb_par);
}


/**
 * cloog_equal_del function :
 * This function reset the equality corresponding to the iterator (level)
 * in the equality matrix (equal).
 * - July 2nd 2002: first version. 
 */
void cloog_equal_del(CloogEqualities *equal, int level)
{ 
    equal->types[level-1] = EQTYPE_NONE;
}



/******************************************************************************
 *                            Processing functions                            *
 ******************************************************************************/

/**
 * Function cloog_constraint_set_normalize:
 * This function will modify the constraint system in such a way that when
 * there is an equality depending on the element at level 'level', there are
 * no more (in)equalities depending on this element. For instance, try
 * test/valilache.cloog with options -f 8 -l 9, with and without the call
 * to this function. At a given moment, for the level L we will have
 * 32*P=L && L>=1 (P is a lower level), this constraint system cannot be
 * translated directly into a source code. Thus, we normalize the domain to
 * remove L from the inequalities. In our example, this leads to
 * 32*P=L && 32*P>=1, that can be transated to the code
 * if (P>=1) { L=32*P ; ... }. This function solves the DaeGon Kim bug.
 * WARNING: Remember that if there is another call to Polylib after a call to
 * this function, we have to recall this function.
 *  -June    16th 2005: first version (adaptation from URGent June-7th-2005 by
 *                      N. Vasilache).
 * - June    21rd 2005: Adaptation for GMP.
 * - November 4th 2005: Complete rewriting, simpler and faster. It is no more an
 *                      adaptation from URGent. 
 */
void cloog_constraint_set_normalize(CloogConstraintSet *constraints, int level)
{ int ref, i, j ;
  cloog_int_t factor_i, factor_ref, temp_i, temp_ref, gcd;
  CloogMatrix *matrix = &constraints->M;
    
  if (matrix == NULL)
  return ;

  /* Don't "normalize" the constant term. */
  if (level == matrix->NbColumns-1)
    return;

  /* Let us find an equality for the current level that can be propagated. */
  for (ref=0;ref<matrix->NbRows;ref++)
  if (cloog_int_is_zero(matrix->p[ref][0]) && !cloog_int_is_zero(matrix->p[ref][level])) {
    cloog_int_init(gcd);
    cloog_int_init(temp_i);
    cloog_int_init(temp_ref);
    cloog_int_init(factor_i);
    cloog_int_init(factor_ref);
  
    /* Row "ref" is the reference equality, now let us find a row to simplify.*/
    for (i=ref+1;i<matrix->NbRows;i++)
    if (!cloog_int_is_zero(matrix->p[i][level])) {
      /* Now let us set to 0 the "level" coefficient of row "j" using "ref".
       * First we compute the factors to apply to each row vector element.
       */
      cloog_int_gcd(gcd, matrix->p[ref][level], matrix->p[i][level]);
      cloog_int_divexact(factor_i, matrix->p[ref][level], gcd);
      cloog_int_divexact(factor_ref, matrix->p[i][level], gcd);
      
      /* Maybe we are simplifying an inequality: factor_i must not be <0. */
      if (cloog_int_is_neg(factor_i)) {
        cloog_int_abs(factor_i, factor_i);
        cloog_int_neg(factor_ref, factor_ref);
      }
      
      /* Now update the vector. */
      for (j=1;j<matrix->NbColumns;j++) {
        cloog_int_mul(temp_i, factor_i, matrix->p[i][j]);
        cloog_int_mul(temp_ref, factor_ref, matrix->p[ref][j]);
        cloog_int_sub(matrix->p[i][j], temp_i, temp_ref);
      }
    
      /* Normalize (divide by GCD of all elements) the updated vector. */
      cloog_seq_normalize(&(matrix->p[i][1]), matrix->NbColumns-1);
    }
    
    cloog_int_clear(gcd);
    cloog_int_clear(temp_i);
    cloog_int_clear(temp_ref);
    cloog_int_clear(factor_i);
    cloog_int_clear(factor_ref);
    break ;
  }
}



/**
 * cloog_constraint_set_copy function:
 * this functions builds and returns a "hard copy" (not a pointer copy) of a
 * CloogMatrix data structure.
 * - October 26th 2005: first version.
 */
CloogConstraintSet *cloog_constraint_set_copy(CloogConstraintSet *constraints)
{ int i, j ;
  CloogMatrix *copy;
  CloogMatrix *matrix = &constraints->M;

  copy = cloog_matrix_alloc(matrix->NbRows, matrix->NbColumns);
  
  for (i=0;i<matrix->NbRows;i++)
  for (j=0;j<matrix->NbColumns;j++)
      cloog_int_set(copy->p[i][j], matrix->p[i][j]);
  
  return cloog_constraint_set_from_cloog_matrix(copy);
}


/**
 * cloog_equal_vector_simplify function:
 * this function simplify an affine expression with its coefficients in
 * "vector" of length "length" thanks to an equality matrix "equal" that gives
 * for some elements of the affine expression an equality with other elements,
 * preferably constants. For instance, if the vector contains i+j+3 and the
 * equality matrix gives i=n and j=2, the vector is simplified to n+3 and is
 * returned in a new vector.
 * - vector is the array of affine expression coefficients
 * - equal is the matrix of equalities,
 * - length is the vector length,
 * - level is a level we don't want to simplify (-1 if none),
 * - nb_par is the number of parameters of the program.
 **
 * - September 20th 2005: first version.
 * - November   2nd 2005: (debug) we are simplifying inequalities, thus we are
 *                        not allowed to multiply the vector by a negative
 *                        constant.Problem found after a report of Michael
 *                        Classen.
 */
struct cloog_vec *cloog_equal_vector_simplify(CloogEqualities *equal, cloog_int_t *vector,
				    int length, int level, int nb_par)
{ int i, j ;
  cloog_int_t gcd, factor_vector, factor_equal, temp_vector, temp_equal;
	struct cloog_vec *simplified;
  
	simplified = cloog_vec_alloc(length);
	cloog_seq_cpy(simplified->p, vector, length);
  
  cloog_int_init(gcd);
  cloog_int_init(temp_vector);
  cloog_int_init(temp_equal);
  cloog_int_init(factor_vector);
  cloog_int_init(factor_equal);
    
  /* For each non-null coefficient in the vector, */
  for (i=length-nb_par-2;i>0;i--)
  if (i != level)
  { /* if the coefficient in not null, and there exists a useful equality */
    if ((!cloog_int_is_zero(simplified->p[i])) && equal->types[i-1])
    { /* Compute the Greatest Common Divisor. */ 
      cloog_int_gcd(gcd, simplified->p[i], equal->constraints->M.p[i-1][i]);
      
      /* Compute the factors to apply to each row vector element. */
      cloog_int_divexact(factor_vector, equal->constraints->M.p[i-1][i], gcd);
      cloog_int_divexact(factor_equal, simplified->p[i], gcd);
      
      /* We are simplifying an inequality: factor_vector must not be <0. */
      if (cloog_int_is_neg(factor_vector)) {
        cloog_int_abs(factor_vector, factor_vector);
        cloog_int_neg(factor_equal, factor_equal);
      }
      
      /* Now update the vector. */
      /* - the iterators, up to the current level, */
      for (j=1;j<=length-nb_par-2;j++) {
        cloog_int_mul(temp_vector, factor_vector, simplified->p[j]);
        cloog_int_mul(temp_equal, factor_equal, equal->constraints->M.p[i-1][j]);
        cloog_int_sub(simplified->p[j], temp_vector, temp_equal);
      }
      /* - between last useful iterator (i) and the first parameter, the equal
       *   matrix is sparse (full of zeroes), we just do nothing there. 
       * - the parameters and the scalar.
       */
      for (j = 0; j < nb_par + 1; j++) {
        cloog_int_mul(temp_vector, factor_vector, simplified->p[length-1-j]);
        cloog_int_mul(temp_equal,factor_equal,
	     equal->constraints->M.p[i-1][equal->constraints->M.NbColumns-j-1]);
        cloog_int_sub(simplified->p[length-1-j],temp_vector,temp_equal) ;
      }
    }
  }
  
  /* Normalize (divide by GCD of all elements) the updated vector. */
  cloog_seq_normalize(&simplified->p[1], length - 1);

  cloog_int_clear(gcd);
  cloog_int_clear(temp_vector);
  cloog_int_clear(temp_equal);
  cloog_int_clear(factor_vector);
  cloog_int_clear(factor_equal);
  
  return simplified ;
}


/**
 * cloog_constraint_set_simplify function:
 * this function simplify all constraints inside the matrix "matrix" thanks to
 * an equality matrix "equal" that gives for some elements of the affine
 * constraint an equality with other elements, preferably constants.
 * For instance, if a row of the matrix contains i+j+3>=0 and the equality
 * matrix gives i=n and j=2, the constraint is simplified to n+3>=0. The
 * simplified constraints are returned back inside a new simplified matrix.
 * - matrix is the set of constraints to simplify,
 * - equal is the matrix of equalities,
 * - level is a level we don't want to simplify (-1 if none),
 * - nb_par is the number of parameters of the program.
 **
 * - November 4th 2005: first version.
 */
CloogConstraintSet *cloog_constraint_set_simplify(CloogConstraintSet *constraints,
	CloogEqualities *equal, int level, int nb_par)
{ int i, j, k ;
	struct cloog_vec *vector;
  CloogMatrix *simplified;
  CloogMatrix *matrix = &constraints->M;
  
  if (matrix == NULL)
  return NULL ;
  
  /* The simplified matrix is such that each row has been simplified thanks
   * tho the "equal" matrix. We allocate the memory for the simplified matrix,
   * then for each row of the original matrix, we compute the simplified
   * vector and we copy its content into the according simplified row.
   */
  simplified = cloog_matrix_alloc(matrix->NbRows, matrix->NbColumns);
  for (i=0;i<matrix->NbRows;i++)
  { vector = cloog_equal_vector_simplify(equal, matrix->p[i],
					  matrix->NbColumns, level, nb_par);
    for (j=0;j<matrix->NbColumns;j++)
    cloog_int_set(simplified->p[i][j], vector->p[j]);
    
    cloog_vec_free(vector);
  }
  
  /* After simplification, it may happen that few constraints are the same,
   * we remove them here by replacing them with 0=0 constraints.
   */
  for (i=0;i<simplified->NbRows;i++)
  for (j=i+1;j<simplified->NbRows;j++)
  { for (k=0;k<simplified->NbColumns;k++)
    if (cloog_int_ne(simplified->p[i][k],simplified->p[j][k]))
    break ;
    
    if (k == matrix->NbColumns)
    { for (k=0;k<matrix->NbColumns;k++)
        cloog_int_set_si(simplified->p[j][k],0);
    }
  }
  
  return cloog_constraint_set_from_cloog_matrix(simplified);
}


/**
 * Return clast_expr corresponding to the variable "level" (1 based) in
 * the given constraint.
 */
struct clast_expr *cloog_constraint_variable_expr(CloogConstraint *constraint,
	int level, CloogNames *names)
{
	int total_dim, nb_iter;
	const char *name;

	total_dim = cloog_constraint_total_dimension(constraint);
	nb_iter = total_dim - names->nb_parameters;

	if (level <= nb_iter)
		name = cloog_names_name_at_level(names, level);
	else
		name = names->parameters[level - (nb_iter+1)] ;

	return &new_clast_name(name)->expr;
}


/**
 * Return true if constraint c involves variable v (zero-based).
 */
int cloog_constraint_involves(CloogConstraint *constraint, int v)
{
	return !cloog_int_is_zero(constraint->line[0][1+v]);
}

int cloog_constraint_is_lower_bound(CloogConstraint *constraint, int v)
{
	return cloog_int_is_pos(constraint->line[0][1+v]);
}

int cloog_constraint_is_upper_bound(CloogConstraint *constraint, int v)
{
	return cloog_int_is_neg(constraint->line[0][1+v]);
}

int cloog_constraint_is_equality(CloogConstraint *constraint)
{
	return cloog_int_is_zero(constraint->line[0][0]);
}

void cloog_constraint_clear(CloogConstraint *constraint)
{
	int k;

	for (k = 1; k <= constraint->set->M.NbColumns - 2; k++)
		cloog_int_set_si(constraint->line[0][k], 0);
}

CloogConstraintSet *cloog_constraint_set_drop_constraint(
	CloogConstraintSet *constraints, CloogConstraint *constraint)
{
	cloog_constraint_clear(constraint);
	return constraints;
}

void cloog_constraint_coefficient_get(CloogConstraint *constraint,
			int var, cloog_int_t *val)
{
	cloog_int_set(*val, constraint->line[0][1+var]);
}

void cloog_constraint_coefficient_set(CloogConstraint *constraint,
			int var, cloog_int_t val)
{
	cloog_int_set(constraint->line[0][1+var], val);
}

void cloog_constraint_constant_get(CloogConstraint *constraint, cloog_int_t *val)
{
	cloog_int_set(*val, constraint->line[0][constraint->set->M.NbColumns-1]);
}

/**
 * Copy the coefficient of constraint c into dst in PolyLib order,
 * i.e., first the coefficients of the variables, then the coefficients
 * of the parameters and finally the constant.
 */
void cloog_constraint_copy_coefficients(CloogConstraint *constraint,
					cloog_int_t *dst)
{
	cloog_seq_cpy(dst, constraint->line[0]+1, constraint->set->M.NbColumns-1);
}

CloogConstraint *cloog_constraint_invalid(void)
{
	return NULL;
}

int cloog_constraint_is_valid(CloogConstraint *constraint)
{
	return constraint != NULL;
}


/**
 * Check whether there is any need for the constraint "upper" on
 * "level" to get reduced.
 * Yes.
 */
int cloog_constraint_needs_reduction(CloogConstraint *upper, int level)
{
	return 1;
}


/**
 * Create a CloogConstraintSet containing enough information to perform
 * a reduction on the upper equality (in this case lower is an invalid
 * CloogConstraint) or the pair of inequalities upper and lower
 * from within insert_modulo_guard.
 * In the PolyLib backend, we return a CloogConstraintSet containting only
 * the upper bound.  The reduction will not change the stride so there
 * will be no need to recompute the bound on the modulo expression.
 */
CloogConstraintSet *cloog_constraint_set_for_reduction(CloogConstraint *upper,
	 CloogConstraint *lower)
{
	CloogConstraintSet *set;

	set = cloog_constraint_set_from_cloog_matrix(
		cloog_matrix_alloc(1, upper->set->M.NbColumns));
	cloog_seq_cpy(set->M.p[0], upper->line[0], set->M.NbColumns);
	return set;
}


/* Computes x, y and g such that g = gcd(a,b) and a*x+b*y = g */
static void Euclid(cloog_int_t a, cloog_int_t b,
			cloog_int_t *x, cloog_int_t *y, cloog_int_t *g)
{
    cloog_int_t c, d, e, f, tmp;

    cloog_int_init(c);
    cloog_int_init(d);
    cloog_int_init(e);
    cloog_int_init(f);
    cloog_int_init(tmp);
    cloog_int_abs(c, a);
    cloog_int_abs(d, b);
    cloog_int_set_si(e, 1);
    cloog_int_set_si(f, 0);
    while (cloog_int_is_pos(d)) {
	cloog_int_tdiv_q(tmp, c, d);
	cloog_int_mul(tmp, tmp, f);
	cloog_int_sub(e, e, tmp);
	cloog_int_tdiv_q(tmp, c, d);
	cloog_int_mul(tmp, tmp, d);
	cloog_int_sub(c, c, tmp);
	cloog_int_swap(c, d);
	cloog_int_swap(e, f);
    }
    cloog_int_set(*g, c);
    if (cloog_int_is_zero(a))
	cloog_int_set_si(*x, 0);
    else if (cloog_int_is_pos(a))
	cloog_int_set(*x, e);
    else cloog_int_neg(*x, e);
    if (cloog_int_is_zero(b))
	cloog_int_set_si(*y, 0);
    else {
	cloog_int_mul(tmp, a, *x);
	cloog_int_sub(tmp, c, tmp);
	cloog_int_divexact(*y, tmp, b);
    }
    cloog_int_clear(c);
    cloog_int_clear(d);
    cloog_int_clear(e);
    cloog_int_clear(f);
    cloog_int_clear(tmp);
}

/**
 * Reduce the modulo guard expressed by "contraints" using equalities
 * found in outer nesting levels (stored in "equal").
 * The modulo guard may be an equality or a pair of inequalities.
 * In case of a pair of inequalities, "constraints" only contains the
 * upper bound and *bound contains the bound on the
 * corresponding modulo expression.  The bound is left untouched by
 * this function.
 */
CloogConstraintSet *cloog_constraint_set_reduce(CloogConstraintSet *constraints,
	int level, CloogEqualities *equal, int nb_par, cloog_int_t *bound)
{
  int i, j, k, len, len2, nb_iter;
  struct cloog_vec *line_vector2;
  cloog_int_t *line, *line2, val, x, y, g;

  len = constraints->M.NbColumns;
  len2 = cloog_equal_total_dimension(equal) + 2;
  nb_iter = len - 2 - nb_par;

  cloog_int_init(val);
  cloog_int_init(x);
  cloog_int_init(y);
  cloog_int_init(g);

  line_vector2 = cloog_vec_alloc(len2);
  line2 = line_vector2->p;

  line = constraints->M.p[0];
  if (cloog_int_is_pos(line[level]))
    cloog_seq_neg(line+1, line+1, len-1);
  cloog_int_neg(line[level], line[level]);
  assert(cloog_int_is_pos(line[level]));

  for (i = nb_iter; i >= 1; --i) {
    if (i == level)
      continue;
    cloog_int_fdiv_r(line[i], line[i], line[level]);
    if (cloog_int_is_zero(line[i]))
      continue;

    /* Look for an earlier variable that is also a multiple of line[level]
     * and check whether we can use the corresponding affine expression
     * to "reduce" the modulo guard, where reduction means that we eliminate
     * a variable, possibly at the expense of introducing other variables
     * with smaller index.
     */
    for (j = level-1; j >= 0; --j) {
      CloogConstraint *equal_constraint;
      if (cloog_equal_type(equal, j+1) != EQTYPE_EXAFFINE)
	continue;
      equal_constraint = cloog_equal_constraint(equal, j);
      cloog_constraint_coefficient_get(equal_constraint, j, &val);
      if (!cloog_int_is_divisible_by(val, line[level])) {
	cloog_constraint_release(equal_constraint);
	continue;
      }
      cloog_constraint_coefficient_get(equal_constraint, i-1, &val);
      if (cloog_int_is_divisible_by(val, line[level])) {
	cloog_constraint_release(equal_constraint);
	continue;
      }
      for (k = j; k > i; --k) {
	cloog_constraint_coefficient_get(equal_constraint, k-1, &val);
	if (cloog_int_is_zero(val))
	  continue;
	if (!cloog_int_is_divisible_by(val, line[level]))
	  break;
      }
      if (k > i) {
	 cloog_constraint_release(equal_constraint);
	 continue;
      }
      cloog_constraint_coefficient_get(equal_constraint, i-1, &val);
      Euclid(val, line[level], &x, &y, &g);
      if (!cloog_int_is_divisible_by(val, line[i])) {
	cloog_constraint_release(equal_constraint);
	continue;
      }
      cloog_int_divexact(val, line[i], g);
      cloog_int_neg(val, val);
      cloog_int_mul(val, val, x);
      cloog_int_set_si(y, 1);
      /* Add (equal->p[j][i])^{-1} * line[i] times the equality */
      cloog_constraint_copy_coefficients(equal_constraint, line2+1);
      cloog_seq_combine(line+1, y, line+1, val, line2+1, i);
      cloog_seq_combine(line+len-nb_par-1, y, line+len-nb_par-1,
					   val, line2+len2-nb_par-1, nb_par+1);
      cloog_constraint_release(equal_constraint);
      break;
    }
  }

  cloog_vec_free(line_vector2);

  cloog_int_clear(val);
  cloog_int_clear(x);
  cloog_int_clear(y);
  cloog_int_clear(g);

  /* Make sure the line is not inverted again in the calling function. */
  cloog_int_neg(line[level], line[level]);

  return constraints;
}

CloogConstraint *cloog_constraint_first(CloogConstraintSet *constraints)
{
	CloogConstraint *c;
	if (constraints->M.NbRows == 0)
		return cloog_constraint_invalid();
	c = ALLOC(CloogConstraint);
	c->set = constraints;
	c->line = &constraints->M.p[0];
	return c;
}

CloogConstraint *cloog_constraint_next(CloogConstraint *constraint)
{
	constraint->line++;
	if (constraint->line == constraint->set->M.p + constraint->set->M.NbRows) {
		cloog_constraint_release(constraint);
		return NULL;
	}
	return constraint;
}

CloogConstraint *cloog_constraint_copy(CloogConstraint *constraint)
{
	CloogConstraint *c = ALLOC(CloogConstraint);
	c->set = constraint->set;
	c->line = constraint->line;
	return c;
}

void cloog_constraint_release(CloogConstraint *constraint)
{
	free(constraint);
}

int cloog_constraint_set_foreach_constraint(CloogConstraintSet *constraints,
	int (*fn)(CloogConstraint *constraint, void *user), void *user)
{
	CloogConstraint *c;

	for (c = cloog_constraint_first(constraints);
	     cloog_constraint_is_valid(c); c = cloog_constraint_next(c))
		if (fn(c, user) < 0) {
			cloog_constraint_release(c);
			return -1;
		}

	return 0;
}

CloogConstraint *cloog_equal_constraint(CloogEqualities *equal, int j)
{
	CloogConstraint *c = ALLOC(CloogConstraint);
	c->set = equal->constraints;
	c->line = &equal->constraints->M.p[j];
	return c;
}