Very slow SA placer based on arachne-pnr
Signed-off-by: David Shah <davey1576@gmail.com>
This commit is contained in:
David Shah
parent
e7d6c4038d
commit
2d993d8ee9
303
common/place.cc
303
common/place.cc
@ -126,11 +126,30 @@ void place_design(Design *design)
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}
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}
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static void place_cell(Design *design, CellInfo *cell, std::mt19937 &rnd)
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struct rnd_state {
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uint32_t state;
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};
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/* The state word must be initialized to non-zero */
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static uint32_t xorshift32(rnd_state &rnd)
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{
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/* Algorithm "xor" from p. 4 of Marsaglia, "Xorshift RNGs" */
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uint32_t x = rnd.state;
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x ^= x << 13;
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x ^= x >> 17;
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x ^= x << 5;
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rnd.state = x;
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return x;
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}
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static float random_float_upto(rnd_state &rnd, float limit) {
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return xorshift32(rnd) / (4294967295 / limit);
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}
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static void place_initial(Design *design, CellInfo *cell, rnd_state &rnd)
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{
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std::uniform_real_distribution<float> random_wirelength(0.0, 30.0);
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float best_distance = std::numeric_limits<float>::infinity();
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BelId best_bel = BelId();
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float best_score = std::numeric_limits<float>::infinity();
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Chip &chip = design->chip;
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if(cell->bel != BelId()) {
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chip.unbindBel(cell->bel);
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@ -140,47 +159,9 @@ static void place_cell(Design *design, CellInfo *cell, std::mt19937 &rnd)
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for (auto bel : chip.getBels()) {
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if (chip.getBelType(bel) == targetType && chip.checkBelAvail(bel) &&
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isValidBelForCell(design, cell, bel)) {
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float distance = 0;
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float belx, bely;
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bool has_conns = false;
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chip.estimatePosition(bel, belx, bely);
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for (auto port : cell->ports) {
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const PortInfo &pi = port.second;
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if (pi.net != nullptr) {
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CellInfo *drv = pi.net->driver.cell;
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//float pin_wirelength = std::numeric_limits<float>::infinity();
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float pin_wirelength = 0;
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if (drv != nullptr && drv->bel != BelId()) {
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float otherx, othery;
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chip.estimatePosition(drv->bel, otherx, othery);
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float local_wl = std::abs(belx - otherx) +
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std::abs(bely - othery);
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//if (local_wl < pin_wirelength)
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pin_wirelength += local_wl;
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has_conns = true;
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}
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if (pi.net->users.size() < 5) {
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for (auto user : pi.net->users) {
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CellInfo *uc = user.cell;
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if (uc != nullptr && uc->bel != BelId()) {
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float otherx, othery;
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chip.estimatePosition(uc->bel, otherx, othery);
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float local_wl = std::abs(belx - otherx) +
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std::abs(bely - othery);
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//if (local_wl < pin_wirelength)
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pin_wirelength += local_wl;
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has_conns = true;
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}
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}
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}
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if (!std::isinf(pin_wirelength))
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distance += pin_wirelength;
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}
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}
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if (!has_conns)
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distance = random_wirelength(rnd);
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if (distance <= best_distance) {
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best_distance = distance;
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float score = random_float_upto(rnd, 1.0);
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if (score <= best_score) {
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best_score = score;
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best_bel = bel;
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}
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}
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@ -196,6 +177,141 @@ static void place_cell(Design *design, CellInfo *cell, std::mt19937 &rnd)
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cell->attrs["BEL"] = chip.getBelName(cell->bel).str();
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}
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struct SAState {
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std::unordered_map<NetInfo *, float> wirelengths;
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float best_wirelength = std::numeric_limits<float>::infinity();
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float temp = 1000;
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bool improved = false;
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int n_move, n_accept;
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int diameter = 35;
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};
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static float get_wirelength(Chip *chip, NetInfo *net) {
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float wirelength = 0;
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float driver_x = 0, driver_y = 0;
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bool consider_driver = false;
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CellInfo *driver_cell = net->driver.cell;
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if (!driver_cell)
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return 0;
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if (driver_cell->bel == BelId())
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return 0;
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consider_driver = chip->estimatePosition(driver_cell->bel, driver_x, driver_y);
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if (!consider_driver)
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return 0;
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for (auto load : net->users) {
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if (load.cell == nullptr)
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continue;
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CellInfo *load_cell = load.cell;
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float load_x = 0, load_y = 0;
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if (load_cell->bel == BelId())
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continue;
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chip->estimatePosition(load_cell->bel, load_x, load_y);
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wirelength += std::abs(load_x - driver_x) + std::abs(load_y - driver_y);
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}
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return wirelength;
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}
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static bool try_swap_position(Design *design, CellInfo *cell, BelId newBel, rnd_state &rnd, SAState &state) {
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std::unordered_set<NetInfo *> update;
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std::unordered_map<NetInfo *, float> new_lengths;
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Chip &chip = design->chip;
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BelId oldBel = cell->bel;
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IdString other = chip.getBelCell(newBel, true);
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CellInfo *other_cell = nullptr;
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float new_wirelength = 0, delta;
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chip.unbindBel(oldBel);
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if (other != IdString()) {
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other_cell = design->cells[other];
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chip.unbindBel(newBel);
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}
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if (!isValidBelForCell(design, cell, newBel))
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goto swap_fail;
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for (const auto &port : cell->ports)
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if (port.second.net != nullptr)
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update.insert(port.second.net);
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if (other != IdString()) {
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if (!isValidBelForCell(design, other_cell, oldBel))
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goto swap_fail;
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for (const auto &port : other_cell->ports)
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if (port.second.net != nullptr)
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update.insert(port.second.net);
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}
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chip.bindBel(newBel, cell->name);
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if (other != IdString()) {
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if (!isValidBelForCell(design, other_cell, oldBel)) {
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chip.unbindBel(newBel);
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goto swap_fail;
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} else {
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chip.bindBel(oldBel, other_cell->name);
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}
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}
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cell->bel = newBel;
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if (other != IdString())
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other_cell->bel = oldBel;
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new_wirelength = state.best_wirelength;
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for (auto net : update) {
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new_wirelength -= state.wirelengths.at(net);
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float net_new_wl = get_wirelength(&chip, net);
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new_wirelength += net_new_wl;
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new_lengths[net] = net_new_wl;
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}
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delta = new_wirelength - state.best_wirelength;
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state.n_move++;
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if (delta < 0 || (state.temp > 1e-6 && random_float_upto(rnd, 1.0) <= std::exp(-delta/state.temp))) {
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state.n_accept++;
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if (delta < 0)
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state.improved = true;
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} else {
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if (other != IdString())
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chip.unbindBel(oldBel);
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chip.unbindBel(newBel);
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goto swap_fail;
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}
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state.best_wirelength = new_wirelength;
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for (auto new_wl : new_lengths)
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state.wirelengths[new_wl.first] = new_wl.second;
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return true;
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swap_fail:
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chip.bindBel(oldBel, cell->name);
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cell->bel = oldBel;
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if (other != IdString()) {
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chip.bindBel(newBel, other);
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other_cell->bel = newBel;
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}
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return false;
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}
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BelId random_bel_for_cell(Design *design, CellInfo *cell, SAState state, rnd_state &rnd)
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{
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BelId best_bel = BelId();
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float best_score = std::numeric_limits<float>::infinity();
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Chip &chip = design->chip;
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BelType targetType = belTypeFromId(cell->type);
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float x = 0, y = 0;
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chip.estimatePosition(cell->bel, x, y);
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for (auto bel : chip.getBels()) {
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if (chip.getBelType(bel) == targetType) {
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float score = random_float_upto(rnd, 1.0);
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float nx = 0, ny = 0;
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chip.estimatePosition(bel, nx, ny);
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if (std::abs(nx - x) > state.diameter || std::abs(ny - y) > state.diameter)
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continue;
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if (score <= best_score) {
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best_score = score;
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best_bel = bel;
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}
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}
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}
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return best_bel;
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}
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void place_design_heuristic(Design *design)
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{
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size_t total_cells = design->cells.size(), placed_cells = 0;
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@ -228,32 +344,97 @@ void place_design_heuristic(Design *design)
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}
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}
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log_info("place_constraints placed %d\n", placed_cells);
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std::mt19937 rnd;
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std::vector<IdString> autoplaced;
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rnd_state rnd;
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rnd.state = 1;
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std::vector<CellInfo *> autoplaced;
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for (auto cell : design->cells) {
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CellInfo *ci = cell.second;
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if (ci->bel == BelId()) {
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place_cell(design, ci, rnd);
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autoplaced.push_back(cell.first);
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place_initial(design, ci, rnd);
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autoplaced.push_back(cell.second);
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placed_cells++;
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}
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log_info("placed %d/%d\n", placed_cells, total_cells);
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}
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for (int i = 0 ; i < 5; i ++) {
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int replaced_cells = 0;
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for (int j = 0; j < autoplaced.size() / 10; j++) {
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design->chip.unbindBel(design->cells.at(autoplaced.at(j))->bel);
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design->cells.at(autoplaced.at(j))->bel = BelId();
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}
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std::shuffle(autoplaced.begin(), autoplaced.end(), rnd);
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for (auto cell : autoplaced) {
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CellInfo *ci = design->cells[cell];
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place_cell(design, ci, rnd);
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replaced_cells++;
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log_info("replaced %d/%d\n", replaced_cells, autoplaced.size());
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}
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SAState state;
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state.best_wirelength = 0;
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for (auto net : design->nets) {
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float wl = get_wirelength(&design->chip, net.second);
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state.wirelengths[net.second] = wl;
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state.best_wirelength += wl;
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}
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int n_no_progress = 0;
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double avg_wirelength = state.best_wirelength;
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state.temp = 10000;
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for (int iter=1;; iter++)
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{
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state.n_move = state.n_accept = 0;
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state.improved = false;
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//if (iter % 50 == 0)
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log(" at iteration #%d: temp = %f, wire length = %f\n", iter, state.temp, state.best_wirelength);
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for (int m = 0; m < 15; ++m)
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{
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for (auto cell : autoplaced)
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{
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BelId try_bel = random_bel_for_cell(design, cell, state, rnd);
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if (try_bel != BelId() && try_bel != cell->bel)
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try_swap_position(design, cell, try_bel, rnd, state);
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}
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}
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if (state.improved)
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{
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n_no_progress = 0;
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// std::cout << "improved\n";
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}
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else
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++n_no_progress;
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if (state.temp <= 1e-3
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/*&& n_no_progress >= 5*/)
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break;
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double Raccept = (double)state.n_accept / (double)state.n_move;
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int M = 30;
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double upper = 0.6,
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lower = 0.4;
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if (state.best_wirelength < 0.95 * avg_wirelength)
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avg_wirelength = 0.8*avg_wirelength + 0.2 * state.best_wirelength;
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else
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{
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if (Raccept >= 0.8)
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{
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state.temp *= 0.7;
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}
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else if (Raccept > upper)
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{
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if (state.diameter < M)
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++state.diameter;
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else
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state.temp *= 0.9;
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}
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else if (Raccept > lower)
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{
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state.temp *= 0.95;
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}
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else
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{
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// Raccept < 0.3
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if (state.diameter > 1)
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--state.diameter;
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else
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state.temp *= 0.8;
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}
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}
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}
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}
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NEXTPNR_NAMESPACE_END
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