lst_idx and lst_vals. more comments.

This commit is contained in:
David Allemang
2022-09-14 16:22:28 -04:00
parent fbad368030
commit c346817743
2 changed files with 43 additions and 28 deletions

View File

@@ -10,9 +10,13 @@ namespace tc {
return {*this, gens};
}
/**
* Each coset is associated a row in each table.
* Rows document the "loops" formed by
*/
struct Row {
int gnr = 0;
int *lst_ptr = nullptr;
size_t lst_idx = -1; // identifies the loop or "family"
};
struct Tables {
@@ -61,24 +65,26 @@ namespace tc {
rel_idx++;
}
int null_lst_ptr;
std::vector<int> lst_vals;
size_t null_lst_idx = 0;
rel_tables.add_row();
for (int table_idx = 0; table_idx < rel_tables.size(); ++table_idx) {
Rel &rel = rel_tables.rels[table_idx];
Row &row = rel_tables.rows[0][table_idx];
if (cosets.get(rel.gens[0]) + cosets.get(rel.gens[1]) == -2) {
row.lst_ptr = new int;
row.lst_idx = lst_vals.size();
lst_vals.push_back(0);
row.gnr = 0;
} else {
row.lst_ptr = &null_lst_ptr;
row.lst_idx = null_lst_idx;
row.gnr = -1;
}
}
// endregion
int idx = 0;
int coset, gen, target, fact_idx, lst, gen_;
int coset, gen, target, fact_idx, lst;
while (true) {
// find next unknown product
@@ -97,74 +103,83 @@ namespace tc {
cosets.add_row();
rel_tables.add_row();
// queue of products that can be determined by the new coset
// queue of products that equal target
std::queue<int> facts;
facts.push(idx);
facts.push(idx); // new product should be recorded and propagated
// todo unrolled linked list interval
// coset = idx / ngens;
// gen = idx % ngens;
// rel_tables.del_rows_to(coset);
// find all products which also lead to target
while (!facts.empty()) {
fact_idx = facts.front();
facts.pop();
// skip if this product was already determined
if (cosets.get(fact_idx) != -1)continue;
// skip if this product was already learned
if (cosets.get(fact_idx) != -1) continue;
cosets.put(fact_idx, target);
coset = fact_idx / ngens;
gen = fact_idx % ngens;
// If the product stays within the coset todo
if (target == coset)
for (int table_idx: gen_map[gen]) {
auto &row = rel_tables.rows[target][table_idx];
auto &trow = rel_tables.rows[target][table_idx];
if (row.lst_ptr == nullptr) {
row.gnr = -1;
if (trow.lst_idx == -1) {
trow.gnr = -1;
}
}
// Test if loop is closed
for (int table_idx: gen_map[gen]) {
auto &rel = rel_tables.rels[table_idx];
auto &trow = rel_tables.rows[target][table_idx];
auto &crow = rel_tables.rows[coset][table_idx];
if (trow.lst_ptr == nullptr) {
trow.lst_ptr = crow.lst_ptr;
auto other_gen = rel.gens[0] == gen ? rel.gens[1] : rel.gens[0];
if (trow.lst_idx == -1) {
trow.lst_idx = crow.lst_idx;
trow.gnr = crow.gnr + 1;
if (crow.gnr < 0)
trow.gnr -= 2;
if (trow.gnr == rel.mult) {
lst = *(trow.lst_ptr);
delete trow.lst_ptr;
gen_ = rel.gens[(int) (rel.gens[0] == gen)];
facts.push(lst * ngens + gen_);
} else if (trow.gnr == -rel.mult) {
gen_ = rel.gens[rel.gens[0] == gen];
facts.push(target * ngens + gen_);
if (trow.gnr == -rel.mult) {
// loop is closed, but internal, so the target links to itself via this generator.
// todo might be able to move this logic up into the (target == coset) block and avoid those computations.
facts.push(target * ngens + other_gen);
} else if (trow.gnr == rel.mult - 1) {
*(trow.lst_ptr) = target;
// loop is almost closed. record that the target closes this loop.
lst_vals[trow.lst_idx] = target;
} else if (trow.gnr == rel.mult) {
// loop is closed. We know the last element in the loop must link with this one.
lst = lst_vals[trow.lst_idx];
// delete trow.lst_ptr;
facts.push(lst * ngens + other_gen);
}
}
}
}
// Find rows which are still not part of any loop, and assign them to a new loop.
for (int table_idx = 0; table_idx < rel_tables.size(); table_idx++) {
auto &rel = rel_tables.rels[table_idx];
auto &trow = rel_tables.rows[target][table_idx];
if (trow.lst_ptr == nullptr) {
if (trow.lst_idx == -1) {
if ((cosets.get(target, rel.gens[0]) != target) and
(cosets.get(target, rel.gens[1]) != target)) {
trow.lst_ptr = new int; // todo slow; memory leak.
trow.lst_idx = lst_vals.size();
lst_vals.push_back(0);
trow.gnr = 0;
} else {
trow.lst_ptr = &null_lst_ptr;
trow.lst_idx = null_lst_idx;
trow.gnr = -1;
}
}