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add simplifiation pass

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2020-02-22 11:21:53 -08:00
parent ab9bcfdcce
commit d1e95a133b
10 changed files with 115 additions and 36 deletions

View file

@ -18,6 +18,7 @@
#include "util/trace.h"
#include "sat/sat_aig_cuts.h"
#include "sat/sat_solver.h"
#include "sat/sat_lut_finder.h"
namespace sat {
@ -762,6 +763,34 @@ namespace sat {
cut2def(on_clause, c, literal(v, true));
}
/**
* simplify a set of cuts by removing don't cares.
*/
void aig_cuts::simplify() {
uint64_t masks[7];
for (unsigned i = 0; i <= 6; ++i) {
masks[i] = cut::effect_mask(i);
}
unsigned dont_cares = 0;
for (cut_set & cs : m_cuts) {
for (cut const& c : cs) {
uint64_t t = c.table();
for (unsigned i = 0; i < std::min(6u, c.size()); ++i) {
uint64_t diff = masks[i] & (t ^ (t >> (1ull << i)));
if (diff == 0ull) {
cut d(c);
d.remove_elem(i);
cs.insert(m_on_cut_add, m_on_cut_del, d);
cs.evict(m_on_cut_del, c);
++dont_cares;
break;
}
}
}
}
IF_VERBOSE(0, verbose_stream() << "#don't cares " << dont_cares << "\n");
}
struct aig_cuts::validator {
aig_cuts& t;
params_ref p;
@ -821,7 +850,7 @@ namespace sat {
cut2def(on_clause, c, literal(v, false));
node2def(on_clause, n, literal(v, true));
val.check();
}
}
std::ostream& aig_cuts::display(std::ostream& out) const {
auto ids = filter_valid_nodes();

View file

@ -227,6 +227,8 @@ namespace sat {
cut_eval simulate(unsigned num_rounds);
void simplify();
std::ostream& display(std::ostream& out) const;
};

View file

@ -107,6 +107,7 @@ namespace sat {
m_cut_delay = p.cut_delay();
m_cut_lut = p.cut_lut();
m_cut_xor = p.cut_xor();
m_cut_dont_cares = p.cut_dont_cares();
m_lookahead_simplify = p.lookahead_simplify();
m_lookahead_double = p.lookahead_double();
m_lookahead_simplify_bca = p.lookahead_simplify_bca();

View file

@ -124,6 +124,7 @@ namespace sat {
unsigned m_cut_delay;
bool m_cut_lut;
bool m_cut_xor;
bool m_cut_dont_cares;
bool m_anf_simplify;
unsigned m_anf_delay;
bool m_anf_exlin;

View file

@ -192,12 +192,13 @@ namespace sat {
m_aig_cuts.add_node(head, ite_op, 3, args);
m_stats.m_xites++;
};
aig_finder af(s);
af.set(on_and);
af.set(on_ite);
clause_vector clauses(s.clauses());
if (m_config.m_learned2aig) clauses.append(s.learned());
af(clauses);
af(clauses);
std::function<void (literal_vector const&)> on_xor =
[&,this](literal_vector const& xors) {
@ -231,13 +232,15 @@ namespace sat {
xf.set(on_xor);
xf(clauses);
}
std::function<void(uint64_t, bool_var_vector const&, bool_var)> on_lut =
[&,this](uint64_t lut, bool_var_vector const& vars, bool_var v) {
m_stats.m_xluts++;
// m_aig_cuts.add_cut(v, lut, vars);
m_aig_cuts.add_node(v, lut, vars.size(), vars.c_ptr());
};
if (s.m_config.m_cut_lut) {
std::function<void(uint64_t, bool_var_vector const&, bool_var)> on_lut =
[&,this](uint64_t lut, bool_var_vector const& vars, bool_var v) {
m_stats.m_xluts++;
// m_aig_cuts.add_cut(v, lut, vars);
m_aig_cuts.add_node(v, lut, vars.size(), vars.c_ptr());
};
lut_finder lf(s);
lf.set(on_lut);
lf(clauses);
@ -567,11 +570,12 @@ namespace sat {
}
void cut_simplifier::add_dont_cares(vector<cut_set> const& cuts) {
if (!m_config.m_enable_dont_cares)
if (!s.m_config.m_cut_dont_cares)
return;
cuts2bins(cuts);
bins2dont_cares();
dont_cares2cuts(cuts);
m_aig_cuts.simplify();
}
/**

View file

@ -89,6 +89,15 @@ namespace sat {
m_cuts[m_size++] = c;
}
void cut_set::evict(on_update_t& on_del, cut const& c) {
for (unsigned i = 0; i < m_size; ++i) {
if (m_cuts[i] == c) {
evict(on_del, i);
break;
}
}
}
void cut_set::evict(on_update_t& on_del, unsigned idx) {
if (m_var != UINT_MAX && on_del) on_del(m_var, m_cuts[idx]);
m_cuts[idx] = m_cuts[--m_size];
@ -166,6 +175,56 @@ namespace sat {
return true;
}
/**
* \brief create the masks
* i = 0: 101010101010101
* i = 1: 1100110011001100
* i = 2: 1111000011110000
* i = 3: 111111110000000011111111
*/
uint64_t cut::effect_mask(unsigned i) {
SASSERT(i <= 6);
uint64_t m = 0;
if (i == 6) {
m = ~((uint64_t)0);
}
else {
m = (1ull << (1u << i)) - 1; // i = 0: m = 1
unsigned w = 1u << (i + 1); // i = 0: w = 2
while (w < 64) {
m |= (m << w); // i = 0: m = 1 + 4
w *= 2;
}
}
return m;
}
/**
remove element from cut as it is deemed a don't care
*/
void cut::remove_elem(unsigned i) {
for (unsigned j = i + 1; j < m_size; ++j) {
m_elems[j-1] = m_elems[j];
}
--m_size;
uint64_t m = effect_mask(i);
uint64_t t = 0;
for (unsigned j = 0, offset = 0; j < 64; ++j) {
if (0 != (m & (1ull << j))) {
t |= ((m_table >> j) & 1u) << offset;
++offset;
}
}
m_table = t;
m_dont_care = 0;
unsigned f = 0;
for (unsigned e : *this) {
f |= (1u << (e & 0x1F));
}
m_filter = f;
}
/**
sat-sweep evaluation. Given 64 bits worth of possible values per variable,
find possible values for function table encoded by cut.

View file

@ -160,6 +160,10 @@ namespace sat {
return true;
}
void remove_elem(unsigned i);
static uint64_t effect_mask(unsigned i);
std::ostream& display(std::ostream& out) const;
static std::ostream& display_table(std::ostream& out, unsigned num_input, uint64_t table);
@ -196,6 +200,7 @@ namespace sat {
std::swap(m_cuts, other.m_cuts);
}
void evict(on_update_t& on_del, unsigned idx);
void evict(on_update_t& on_del, cut const& c);
std::ostream& display(std::ostream& out) const;
};

View file

@ -32,7 +32,9 @@ namespace sat {
// max_size = 6 -> 64 bits
SASSERT(sizeof(m_combination)*8 >= (1ull << static_cast<uint64_t>(max_size)));
init_clause_filter();
for (unsigned i = 0; i <= 6; ++i) init_mask(i);
for (unsigned i = 0; i <= 6; ++i) {
m_masks[i] = cut::effect_mask(i);
}
m_var_position.resize(s.num_vars());
for (clause* cp : clauses) {
cp->unmark_used();
@ -203,31 +205,6 @@ namespace sat {
return false;
}
/**
* \brief create the masks
* i = 0: 101010101010101
* i = 1: 1100110011001100
* i = 2: 1111000011110000
* i = 3: 111111110000000011111111
*/
void lut_finder::init_mask(unsigned i) {
SASSERT(i <= 6);
uint64_t m = 0;
if (i == 6) {
m = ~((uint64_t)0);
}
else {
m = (1ull << (1u << i)) - 1; // i = 0: m = 1
unsigned w = 1u << (i + 1); // i = 0: w = 2
while (w < 64) {
m |= (m << w); // i = 0: m = 1 + 4
w *= 2;
}
}
m_masks[i] = m;
}
/**
* \brief check if all output combinations for variable i are defined.
*/

View file

@ -61,7 +61,6 @@ namespace sat {
bool extract_lut(literal l1, literal l2);
bool extract_lut(clause& c2);
bool update_combinations(unsigned mask);
void init_mask(unsigned i);
void init_clause_filter();
void init_clause_filter(clause_vector& clauses);
unsigned get_clause_filter(clause const& c);
@ -75,5 +74,6 @@ namespace sat {
unsigned max_lut_size() const { return m_max_lut_size; }
void operator()(clause_vector& clauses);
};
}

View file

@ -77,6 +77,7 @@ def_module_params('sat',
('cut.delay', UINT, 2, 'delay cut simplification by in-processing round'),
('cut.lut', BOOL, False, 'extract luts from clauses for cut simplification'),
('cut.xor', BOOL, False, 'extract xors from clauses for cut simplification'),
('cut.dont_cares', BOOL, True, 'integrate dont cares with cuts'),
('lookahead.cube.cutoff', SYMBOL, 'depth', 'cutoff type used to create lookahead cubes: depth, freevars, psat, adaptive_freevars, adaptive_psat'),
# - depth: the maximal cutoff is fixed to the value of lookahead.cube.depth.
# So if the value is 10, at most 1024 cubes will be generated of length 10.