placer1: Allow chain position swaps after legalisation
Signed-off-by: David Shah <davey1576@gmail.com>
This commit is contained in:
David Shah
David Shah
parent
3650c8a0e7
commit
23306c163f
@ -304,7 +304,7 @@ class ConstraintLegaliseWorker
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// Set the strength to locked on all cells in chain
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void lockdown_chain(CellInfo *root)
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{
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root->belStrength = STRENGTH_LOCKED;
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root->belStrength = STRENGTH_STRONG;
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for (auto child : root->constr_children)
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lockdown_chain(child);
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}
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@ -380,7 +380,7 @@ class ConstraintLegaliseWorker
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rippedCells.insert(confl_cell->name);
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}
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}
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ctx->bindBel(target, ctx->cells.at(cp.first).get(), STRENGTH_LOCKED);
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ctx->bindBel(target, ctx->cells.at(cp.first).get(), STRENGTH_STRONG);
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rippedCells.erase(cp.first);
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}
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for (auto cp : solution) {
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@ -24,6 +24,7 @@
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#include "placer1.h"
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#include <algorithm>
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#include <boost/lexical_cast.hpp>
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#include <boost/range/adaptor/reversed.hpp>
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#include <chrono>
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#include <cmath>
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#include <iostream>
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@ -42,6 +43,8 @@
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#include "place_common.h"
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#include "timing.h"
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#include "util.h"
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namespace std {
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template <> struct hash<std::pair<NEXTPNR_NAMESPACE_PREFIX IdString, std::size_t>>
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{
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@ -152,6 +155,8 @@ class SAPlacer
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// Sort to-place cells for deterministic initial placement
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std::vector<CellInfo *> autoplaced;
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std::vector<CellInfo *> chain_basis;
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for (auto &cell : ctx->cells) {
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CellInfo *ci = cell.second.get();
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if (ci->bel == BelId()) {
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@ -219,6 +224,13 @@ class SAPlacer
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if (try_bel != BelId() && try_bel != cell->bel)
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try_swap_position(cell, try_bel);
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}
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// Also try swapping chains, if applicable
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for (auto cb : chain_basis) {
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Loc chain_base_loc = ctx->getBelLocation(cb->bel);
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BelId try_base = random_bel_for_cell(cb, chain_base_loc.z);
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if (try_base != BelId() && try_base != cb->bel)
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try_swap_chain(cb, try_base);
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}
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}
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if (curr_wirelen_cost < min_wirelen) {
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@ -276,8 +288,11 @@ class SAPlacer
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if (legalise_relative_constraints(ctx)) {
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// Only increase temperature if something was moved
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autoplaced.clear();
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chain_basis.clear();
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for (auto cell : sorted(ctx->cells)) {
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if (cell.second->belStrength < STRENGTH_STRONG)
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if (cell.second->belStrength <= STRENGTH_STRONG && cell.second->constr_parent == nullptr && !cell.second->constr_children.empty())
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chain_basis.push_back(cell.second);
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else if (cell.second->belStrength < STRENGTH_STRONG)
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autoplaced.push_back(cell.second);
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}
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temp = post_legalise_temp;
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@ -458,9 +473,101 @@ class SAPlacer
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return false;
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}
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inline bool is_constrained(CellInfo *cell) {
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return cell->constr_parent != nullptr || !cell->constr_children.empty();
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}
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// Swap the Bel of a cell with another, return the original location
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BelId swap_cell_bels(CellInfo *cell, BelId newBel) {
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BelId oldBel = cell->bel;
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CellInfo *bound = ctx->getBoundBelCell(newBel);
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if (bound != nullptr)
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ctx->unbindBel(newBel);
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ctx->unbindBel(oldBel);
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ctx->bindBel(newBel, cell, is_constrained(cell) ? STRENGTH_STRONG : STRENGTH_WEAK);
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if (bound != nullptr)
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ctx->bindBel(oldBel, bound, is_constrained(bound) ? STRENGTH_STRONG : STRENGTH_WEAK);
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return oldBel;
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}
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// Discover the relative positions of all cells in a chain
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void discover_chain(Loc baseLoc, CellInfo *cell, std::vector<std::pair<CellInfo*, Loc>> &cell_rel) {
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Loc cellLoc = ctx->getBelLocation(cell->bel);
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Loc rel{cellLoc.x - baseLoc.x, cellLoc.y - baseLoc.y, cellLoc.z};
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cell_rel.emplace_back(std::make_pair(cell, rel));
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for (auto child : cell->constr_children)
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discover_chain(baseLoc, child, cell_rel);
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}
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// Attempt to swap a chain with a non-chain
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bool try_swap_chain(CellInfo *cell, BelId newBase) {
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std::vector<std::pair<CellInfo *, Loc>> cell_rel;
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std::unordered_set<IdString> cells;
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std::vector<std::pair<CellInfo*, BelId>> moves_made;
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std::vector<std::pair<CellInfo *, BelId>> dest_bels;
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double delta = 0;
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moveChange.reset();
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log_info("finding cells for chain swap %s\n", cell->name.c_str(ctx));
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Loc baseLoc = ctx->getBelLocation(cell->bel);
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discover_chain(baseLoc, cell, cell_rel);
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Loc newBaseLoc = ctx->getBelLocation(newBase);
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NPNR_ASSERT(newBaseLoc.z == baseLoc.z);
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for (const auto &cr : cell_rel)
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cells.insert(cr.first->name);
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for (const auto &cr : cell_rel) {
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Loc targetLoc = {newBaseLoc.x + cr.second.x, newBaseLoc.y + cr.second.y, cr.second.z};
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BelId targetBel = ctx->getBelByLocation(targetLoc);
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if (targetBel == BelId())
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return false;
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if (ctx->getBelType(targetBel) != cell->type)
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return false;
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CellInfo *bound = ctx->getBoundBelCell(targetBel);
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// We don't consider swapping chains with other chains, at least for the time being - unless it is
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// part of this chain
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if (bound != nullptr && !cells.count(bound->name) && (bound->belStrength >= STRENGTH_STRONG || is_constrained(bound)))
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return false;
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dest_bels.emplace_back(std::make_pair(cr.first, targetBel));
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}
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log_info("trying chain swap %s\n", cell->name.c_str(ctx));
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// <cell, oldBel>
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for (const auto &db : dest_bels) {
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BelId oldBel = swap_cell_bels(db.first, db.second);
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moves_made.emplace_back(std::make_pair(db.first, oldBel));
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}
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for (const auto &mm : moves_made) {
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if (!ctx->isBelLocationValid(mm.first->bel))
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goto swap_fail;
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if (!ctx->isBelLocationValid(mm.second))
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goto swap_fail;
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add_move_cell(moveChange, mm.first, mm.second);
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CellInfo *bound = ctx->getBoundBelCell(mm.second);
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if (bound != nullptr)
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add_move_cell(moveChange, bound, mm.first->bel);
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}
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compute_cost_changes(moveChange);
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delta = lambda * (moveChange.timing_delta / last_timing_cost) +
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(1 - lambda) * (double(moveChange.wirelen_delta) / last_wirelen_cost);
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n_move++;
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// SA acceptance criterea
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if (delta < 0 || (temp > 1e-8 && (ctx->rng() / float(0x3fffffff)) <= std::exp(-delta / temp))) {
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n_accept++;
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log_info("accepted chain swap %s\n", cell->name.c_str(ctx));
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} else {
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goto swap_fail;
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}
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commit_cost_changes(moveChange);
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return true;
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swap_fail:
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for (const auto &entry : boost::adaptors::reverse(moves_made))
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swap_cell_bels(entry.first, entry.second);
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return false;
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}
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// Find a random Bel of the correct type for a cell, within the specified
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// diameter
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BelId random_bel_for_cell(CellInfo *cell)
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BelId random_bel_for_cell(CellInfo *cell, int force_z = -1)
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{
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IdString targetType = cell->type;
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Loc curr_loc = ctx->getBelLocation(cell->bel);
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@ -479,6 +586,11 @@ class SAPlacer
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if (fb.size() == 0)
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continue;
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BelId bel = fb.at(ctx->rng(int(fb.size())));
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if (force_z != -1) {
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Loc loc = ctx->getBelLocation(bel);
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if (loc.z != force_z)
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continue;
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}
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if (locked_bels.find(bel) != locked_bels.end())
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continue;
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return bel;
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