Module: ppl/ppl Branch: pip Commit: 0e4098c48d6fe9daae9d405112df1aac7ed66742 URL: http://www.cs.unipr.it/git/gitweb.cgi?p=ppl/ppl.git;a=commit;h=0e4098c48d6fe...

Author: Enea Zaffanella zaffanella@cs.unipr.it Date: Thu Feb 10 10:46:03 2011 +0100

Exploit variable integrality when creating tautology constraints. Factored out helper function void integral_simplification(Row&); used when generating tautology and sign splitting constraints.

---

src/PIP_Tree.cc | 67 ++++++++++++++++++++++++++++++------------------------ 1 files changed, 37 insertions(+), 30 deletions(-)

diff --git a/src/PIP_Tree.cc b/src/PIP_Tree.cc index 1a21047..38a30e5 100644 --- a/src/PIP_Tree.cc +++ b/src/PIP_Tree.cc @@ -488,6 +488,33 @@ gcd_assign_iter(Coefficient& gcd, Iter first, Iter last) { } }

+// Simplify row by exploiting variable integrality. +void +integral_simplification(Row& row) { + if (row[0] != 0) { + Row::const_iterator j_begin = row.begin(); + Row::const_iterator j_end = row.end(); + PPL_ASSERT(j_begin != j_end && j_begin.index() == 0 && *j_begin != 0); + /* Find next column with a non-zero value (there should be one). */ + ++j_begin; + PPL_ASSERT(j_begin != j_end); + for ( ; *j_begin == 0; ++j_begin) + PPL_ASSERT(j_begin != j_end); + /* Use it to initialize gcd. */ + PPL_DIRTY_TEMP_COEFFICIENT(gcd); + gcd = *j_begin; + ++j_begin; + gcd_assign_iter(gcd, j_begin, j_end); + if (gcd != 1) { + PPL_DIRTY_TEMP_COEFFICIENT(mod); + pos_mod_assign(mod, row[0], gcd); + row[0] -= mod; + } + } + /* Final normalization. */ + row.normalize(); +} + // Divide all coefficients in row x and denominator y by their GCD. void row_normalize(Row& x, Coefficient& den) { @@ -2730,25 +2757,26 @@ PIP_Solution_Node::solve(const PIP_Problem& pip, }

if (i_neg != not_a_dim) { - Row copy = tableau.t[i_neg]; - copy.normalize(); - context.add_row(copy); - add_constraint(copy, all_params); + Row tautology = tableau.t[i_neg]; + /* Simplify tautology by exploiting integrality. */ + integral_simplification(tautology); + context.add_row(tautology); + add_constraint(tautology, all_params); sign[i_neg] = POSITIVE; #ifdef NOISY_PIP { - Linear_Expression expr = Linear_Expression(copy.get(0)); + Linear_Expression expr = Linear_Expression(tautology.get(0)); dimension_type j = 1; for (Variables_Set::const_iterator p = all_params.begin(), p_end = all_params.end(); p != p_end; ++p, ++j) - add_mul_assign(expr, copy.get(j), Variable(*p)); - Constraint tautology(expr >= 0); + add_mul_assign(expr, tautology.get(j), Variable(*p)); using namespace IO_Operators; std::cerr << std::setw(2 * indent_level) << "" << "Row " << i_neg << ": mixed param sign, negative var coeffs\n"; std::cerr << std::setw(2 * indent_level) << "" - << "==> adding tautology: " << tautology << ".\n"; + << "==> adding tautology: " + << Constraint(expr >= 0) << ".\n"; } #endif // #ifdef NOISY_PIP // Jump to next iteration. @@ -2776,28 +2804,7 @@ PIP_Solution_Node::solve(const PIP_Problem& pip,

Row t_test(tableau.t[best_i]); /* Simplify t_test by exploiting integrality. */ - if (t_test[0] != 0) { - Row::const_iterator j_begin = t_test.begin(); - Row::const_iterator j_end = t_test.end(); - PPL_ASSERT(j_begin != j_end && j_begin.index() == 0 && *j_begin != 0); - /* Find next column with a non-zero value (there should be one). */ - ++j_begin; - PPL_ASSERT(j_begin != j_end); - for ( ; *j_begin == 0; ++j_begin) - PPL_ASSERT(j_begin != j_end); - /* Use it to initialize gcd. */ - PPL_DIRTY_TEMP_COEFFICIENT(gcd); - gcd = *j_begin; - ++j_begin; - gcd_assign_iter(gcd, j_begin, j_end); - if (gcd != 1) { - PPL_DIRTY_TEMP_COEFFICIENT(mod); - pos_mod_assign(mod, t_test[0], gcd); - t_test[0] -= mod; - } - } - /* Normalize t_test. */ - t_test.normalize(); + integral_simplification(t_test);

#ifdef NOISY_PIP {