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Using LFSR counter for ezSAT::manyhot() 

The only user of this API right now is the puzzle3d benchmark and
it sees a slight reduction in CNF size from this, but the performance
difference is within the noise of measurement on my system.

Signed-off-by: Claire Wolf <claire@symbioticeda.com>
This commit is contained in:
Claire Wolf 2020-03-17 14:15:08 +01:00
parent c90324662c
commit f72b65b2a5
1 changed files with 118 additions and 0 deletions
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118
libs/ezsat/ezsat.cc
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@ -1389,6 +1389,7 @@ int ezSAT::onehot(const std::vector<int> &vec, bool max_only)
return expression(OpAnd, formula);
}
#if 0
int ezSAT::manyhot(const std::vector<int> &vec, int min_hot, int max_hot)
{
// many-hot encoding using a simple sorting network
@ -1426,6 +1427,123 @@ int ezSAT::manyhot(const std::vector<int> &vec, int min_hot, int max_hot)
return expression(OpAnd, formula);
}
#else
static std::vector<int> lfsr_sym(ezSAT *that, const std::vector<int> &vec, int poly)
{
std::vector<int> out;
for (int i = 0; i < int(vec.size()); i++)
if ((poly & (1 << (i+1))) != 0) {
if (out.empty())
out.push_back(vec.at(i));
else
out.at(0) = that->XOR(out.at(0), vec.at(i));
}
for (int i = 0; i+1 < int(vec.size()); i++)
out.push_back(vec.at(i));
return out;
}
static int lfsr_num(int vec, int poly, int cnt = 1)
{
int mask = poly >> 1;
mask |= mask >> 1;
mask |= mask >> 2;
mask |= mask >> 4;
mask |= mask >> 8;
mask |= mask >> 16;
while (cnt-- > 0) {
int bits = vec & (poly >> 1);
bits = ((bits & 0xAAAAAAAA) >> 1) ^ (bits & 0x55555555);
bits = ((bits & 0x44444444) >> 2) ^ (bits & 0x11111111);
bits = ((bits & 0x10101010) >> 4) ^ (bits & 0x01010101);
bits = ((bits & 0x01000100) >> 8) ^ (bits & 0x00010001);
bits = ((bits & 0x00010000) >> 16) ^ (bits & 0x00000001);
vec = ((vec << 1) | bits) & mask;
}
return vec;
}
int ezSAT::manyhot(const std::vector<int> &vec, int min_hot, int max_hot)
{
// many-hot encoding using LFSR as counter
int poly = 0;
int nbits = 0;
if (vec.size() < 3) {
poly = (1 << 2) | (1 << 1) | 1;
nbits = 2;
} else
if (vec.size() < 7) {
poly = (1 << 3) | (1 << 2) | 1;
nbits = 3;
} else
if (vec.size() < 15) {
poly = (1 << 4) | (1 << 3) | 1;
nbits = 4;
} else
if (vec.size() < 31) {
poly = (1 << 5) | (1 << 3) | 1;
nbits = 5;
} else
if (vec.size() < 63) {
poly = (1 << 6) | (1 << 5) | 1;
nbits = 6;
} else
if (vec.size() < 127) {
poly = (1 << 7) | (1 << 6) | 1;
nbits = 7;
} else
// if (vec.size() < 255) {
// poly = (1 << 8) | (1 << 6) | (1 << 5) | (1 << 4) | 1;
// nbits = 8;
// } else
if (vec.size() < 511) {
poly = (1 << 9) | (1 << 5) | 1;
nbits = 9;
} else {
assert(0);
}
std::vector<int> min_val;
std::vector<int> max_val;
if (min_hot > 1)
min_val = vec_const_unsigned(lfsr_num(1, poly, min_hot), nbits);
if (max_hot >= 0)
max_val = vec_const_unsigned(lfsr_num(1, poly, max_hot+1), nbits);
std::vector<int> state = vec_const_unsigned(1, nbits);
std::vector<int> match_min;
std::vector<int> match_max;
if (min_hot == 1)
match_min = vec;
for (int i = 0; i < int(vec.size()); i++)
{
state = vec_ite(vec[i], lfsr_sym(this, state, poly), state);
if (!min_val.empty() && i+1 >= min_hot)
match_min.push_back(vec_eq(min_val, state));
if (!max_val.empty() && i >= max_hot)
match_max.push_back(vec_eq(max_val, state));
}
int min_matched = min_hot ? vec_reduce_or(match_min) : CONST_TRUE;
int max_matched = vec_reduce_or(match_max);
return AND(min_matched, NOT(max_matched));
}
#endif
int ezSAT::ordered(const std::vector<int> &vec1, const std::vector<int> &vec2, bool allow_equal)
{