Renamed placer to Simulated-Annealing placer

1 files changed, 393 insertions, 0 deletions

diff --git a/common/place_sa.cc b/common/place_sa.cc
new file mode 100644
index 00000000..a6d3040f
--- /dev/null
+++ b/common/place_sa.cc
@@ -0,0 +1,393 @@
+/*
+ *  nextpnr -- Next Generation Place and Route
+ *
+ *  Copyright (C) 2018  Clifford Wolf <clifford@clifford.at>
+ *
+ *  Permission to use, copy, modify, and/or distribute this software for any
+ *  purpose with or without fee is hereby granted, provided that the above
+ *  copyright notice and this permission notice appear in all copies.
+ *
+ *  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ *  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ *  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ *  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ *  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ *  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ *  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ */
+
+#include "place.h"
+#include <algorithm>
+#include <cmath>
+#include <iostream>
+#include <limits>
+#include <list>
+#include <map>
+#include <ostream>
+#include <queue>
+#include <random>
+#include <set>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <vector>
+#include "arch_place.h"
+#include "log.h"
+
+NEXTPNR_NAMESPACE_BEGIN
+
+struct rnd_state
+{
+    uint32_t state;
+};
+
+/* The state word must be initialized to non-zero */
+static uint32_t xorshift32(rnd_state &rnd)
+{
+    /* Algorithm "xor" from p. 4 of Marsaglia, "Xorshift RNGs" */
+    uint32_t x = rnd.state;
+    x ^= x << 13;
+    x ^= x >> 17;
+    x ^= x << 5;
+    rnd.state = x;
+    return x;
+}
+
+static float random_float_upto(rnd_state &rnd, float limit)
+{
+    return xorshift32(rnd) / (4294967296 / limit);
+}
+
+static int random_int_between(rnd_state &rnd, int a, int b)
+{
+    return a + int(random_float_upto(rnd, b - a));
+}
+
+// Initial random placement
+static void place_initial(Design *design, CellInfo *cell, rnd_state &rnd)
+{
+    BelId best_bel = BelId();
+    float best_score = std::numeric_limits<float>::infinity();
+    Chip &chip = design->chip;
+    if (cell->bel != BelId()) {
+        chip.unbindBel(cell->bel);
+        cell->bel = BelId();
+    }
+    BelType targetType = belTypeFromId(cell->type);
+    for (auto bel : chip.getBels()) {
+        if (chip.getBelType(bel) == targetType && chip.checkBelAvail(bel) &&
+            isValidBelForCell(design, cell, bel)) {
+            float score = random_float_upto(rnd, 1.0);
+            if (score <= best_score) {
+                best_score = score;
+                best_bel = bel;
+            }
+        }
+    }
+    if (best_bel == BelId()) {
+        log_error("failed to place cell '%s' of type '%s'\n",
+                  cell->name.c_str(), cell->type.c_str());
+    }
+    cell->bel = best_bel;
+    chip.bindBel(cell->bel, cell->name);
+
+    // Back annotate location
+    cell->attrs["BEL"] = chip.getBelName(cell->bel).str();
+}
+
+// Stores the state of the SA placer
+struct SAState
+{
+    std::unordered_map<NetInfo *, float> wirelengths;
+    float curr_wirelength = std::numeric_limits<float>::infinity();
+    float temp = 1000;
+    bool improved = false;
+    int n_move, n_accept;
+    int diameter = 35;
+    std::vector<std::vector<std::vector<std::vector<BelId>>>> fast_bels;
+};
+
+// Get the total estimated wirelength for a net
+static float get_wirelength(Chip *chip, NetInfo *net)
+{
+    float wirelength = 0;
+    int driver_x = 0, driver_y = 0;
+    bool consider_driver = false;
+    CellInfo *driver_cell = net->driver.cell;
+    if (!driver_cell)
+        return 0;
+    if (driver_cell->bel == BelId())
+        return 0;
+    consider_driver =
+            chip->estimatePosition(driver_cell->bel, driver_x, driver_y);
+    WireId drv_wire = chip->getWireBelPin(driver_cell->bel,
+                                          portPinFromId(net->driver.port));
+    if (!consider_driver)
+        return 0;
+    for (auto load : net->users) {
+        if (load.cell == nullptr)
+            continue;
+        CellInfo *load_cell = load.cell;
+        int load_x = 0, load_y = 0;
+        if (load_cell->bel == BelId())
+            continue;
+        // chip->estimatePosition(load_cell->bel, load_x, load_y);
+        WireId user_wire =
+                chip->getWireBelPin(load_cell->bel, portPinFromId(load.port));
+        // wirelength += std::abs(load_x - driver_x) + std::abs(load_y -
+        // driver_y);
+        wirelength += chip->estimateDelay(drv_wire, user_wire);
+    }
+    return wirelength;
+}
+
+// Attempt a SA position swap, return true on success or false on failure
+static bool try_swap_position(Design *design, CellInfo *cell, BelId newBel,
+                              rnd_state &rnd, SAState &state)
+{
+    static std::unordered_set<NetInfo *> update;
+    static std::vector<std::pair<NetInfo *, float>> new_lengths;
+    new_lengths.clear();
+    update.clear();
+    Chip &chip = design->chip;
+    BelId oldBel = cell->bel;
+    IdString other = chip.getBelCell(newBel, true);
+    CellInfo *other_cell = nullptr;
+    float new_wirelength = 0, delta;
+    chip.unbindBel(oldBel);
+    if (other != IdString()) {
+        other_cell = design->cells[other];
+        chip.unbindBel(newBel);
+    }
+    if (!isValidBelForCell(design, cell, newBel))
+        goto swap_fail;
+
+    for (const auto &port : cell->ports)
+        if (port.second.net != nullptr)
+            update.insert(port.second.net);
+
+    if (other != IdString()) {
+        if (!isValidBelForCell(design, other_cell, oldBel))
+            goto swap_fail;
+        for (const auto &port : other_cell->ports)
+            if (port.second.net != nullptr)
+                update.insert(port.second.net);
+    }
+
+    chip.bindBel(newBel, cell->name);
+    if (other != IdString()) {
+        if (!isValidBelForCell(design, other_cell, oldBel)) {
+            chip.unbindBel(newBel);
+            goto swap_fail;
+        } else {
+            chip.bindBel(oldBel, other_cell->name);
+        }
+    }
+
+    cell->bel = newBel;
+    if (other != IdString())
+        other_cell->bel = oldBel;
+
+    new_wirelength = state.curr_wirelength;
+
+    // Recalculate wirelengths for all nets touched by the peturbation
+    for (auto net : update) {
+        new_wirelength -= state.wirelengths.at(net);
+        float net_new_wl = get_wirelength(&chip, net);
+        new_wirelength += net_new_wl;
+        new_lengths.push_back(std::make_pair(net, net_new_wl));
+    }
+    delta = new_wirelength - state.curr_wirelength;
+    state.n_move++;
+    // SA acceptance criterea
+    if (delta < 0 ||
+        (state.temp > 1e-6 &&
+         random_float_upto(rnd, 1.0) <= std::exp(-delta / state.temp))) {
+        state.n_accept++;
+        if (delta < 0)
+            state.improved = true;
+    } else {
+        if (other != IdString())
+            chip.unbindBel(oldBel);
+        chip.unbindBel(newBel);
+        goto swap_fail;
+    }
+    state.curr_wirelength = new_wirelength;
+    for (auto new_wl : new_lengths)
+        state.wirelengths.at(new_wl.first) = new_wl.second;
+
+    return true;
+swap_fail:
+    chip.bindBel(oldBel, cell->name);
+    cell->bel = oldBel;
+    if (other != IdString()) {
+        chip.bindBel(newBel, other);
+        other_cell->bel = newBel;
+    }
+    return false;
+}
+
+// Find a random Bel of the correct type for a cell, within the specified
+// diameter
+BelId random_bel_for_cell(Design *design, CellInfo *cell, SAState &state,
+                          rnd_state &rnd)
+{
+    BelId best_bel = BelId();
+    Chip &chip = design->chip;
+    BelType targetType = belTypeFromId(cell->type);
+    assert(int(targetType) < state.fast_bels.size());
+    int x = 0, y = 0;
+    chip.estimatePosition(cell->bel, x, y);
+    while (true) {
+        int nx = random_int_between(rnd, std::max(int(x) - state.diameter, 0),
+                                    int(x) + state.diameter + 1);
+        int ny = random_int_between(rnd, std::max(int(y) - state.diameter, 0),
+                                    int(y) + state.diameter + 1);
+        if (nx >= state.fast_bels.at(int(targetType)).size())
+            continue;
+        if (ny >= state.fast_bels.at(int(targetType)).at(nx).size())
+            continue;
+        const auto &fb = state.fast_bels.at(int(targetType)).at(nx).at(ny);
+        if (fb.size() == 0)
+            continue;
+        return fb.at(random_int_between(rnd, 0, fb.size()));
+    }
+}
+
+void place_design_sa(Design *design)
+{
+    size_t total_cells = design->cells.size(), placed_cells = 0;
+    std::queue<CellInfo *> visit_cells;
+    // Initial constraints placer
+    for (auto cell_entry : design->cells) {
+        CellInfo *cell = cell_entry.second;
+        auto loc = cell->attrs.find("BEL");
+        if (loc != cell->attrs.end()) {
+            std::string loc_name = loc->second;
+            BelId bel = design->chip.getBelByName(IdString(loc_name));
+            if (bel == BelId()) {
+                log_error("No Bel named \'%s\' located for "
+                          "this chip (processing BEL attribute on \'%s\')\n",
+                          loc_name.c_str(), cell->name.c_str());
+            }
+
+            BelType bel_type = design->chip.getBelType(bel);
+            if (bel_type != belTypeFromId(cell->type)) {
+                log_error("Bel \'%s\' of type \'%s\' does not match cell "
+                          "\'%s\' of type \'%s\'",
+                          loc_name.c_str(), belTypeToId(bel_type).c_str(),
+                          cell->name.c_str(), cell->type.c_str());
+            }
+
+            cell->bel = bel;
+            design->chip.bindBel(bel, cell->name);
+            placed_cells++;
+            visit_cells.push(cell);
+        }
+    }
+    log_info("place_constraints placed %d\n", int(placed_cells));
+    rnd_state rnd;
+    rnd.state = 1;
+    std::vector<CellInfo *> autoplaced;
+    SAState state;
+    // Place cells randomly initially
+    for (auto cell : design->cells) {
+        CellInfo *ci = cell.second;
+        if (ci->bel == BelId()) {
+            place_initial(design, ci, rnd);
+            autoplaced.push_back(cell.second);
+            placed_cells++;
+        }
+        log_info("placed %d/%d\n", int(placed_cells), int(total_cells));
+    }
+    // Build up a fast position/type to Bel lookup table
+    int max_x = 0, max_y = 0;
+    for (auto bel : design->chip.getBels()) {
+        int x, y;
+        design->chip.estimatePosition(bel, x, y);
+        BelType type = design->chip.getBelType(bel);
+        if (state.fast_bels.size() < int(type) + 1)
+            state.fast_bels.resize(int(type) + 1);
+        if (state.fast_bels.at(int(type)).size() < int(x) + 1)
+            state.fast_bels.at(int(type)).resize(int(x) + 1);
+        if (state.fast_bels.at(int(type)).at(int(x)).size() < int(y) + 1)
+            state.fast_bels.at(int(type)).at(int(x)).resize(int(y) + 1);
+        max_x = std::max(max_x, int(x));
+        max_y = std::max(max_y, int(y));
+        state.fast_bels.at(int(type)).at(int(x)).at(int((y))).push_back(bel);
+    }
+    state.diameter = std::max(max_x, max_y) + 1;
+    // Calculate wirelength after initial placement
+    state.curr_wirelength = 0;
+    for (auto net : design->nets) {
+        float wl = get_wirelength(&design->chip, net.second);
+        state.wirelengths[net.second] = wl;
+        state.curr_wirelength += wl;
+    }
+
+    int n_no_progress = 0;
+    double avg_wirelength = state.curr_wirelength;
+    state.temp = 10000;
+
+    // Main simulated annealing loop
+    for (int iter = 1;; iter++) {
+        state.n_move = state.n_accept = 0;
+        state.improved = false;
+
+        // if (iter % 50 == 0)
+        log("  at iteration #%d: temp = %f, wire length = %f\n", iter,
+            state.temp, state.curr_wirelength);
+
+        for (int m = 0; m < 15; ++m) {
+            // Loop through all automatically placed cells
+            for (auto cell : autoplaced) {
+                // Find another random Bel for this cell
+                BelId try_bel = random_bel_for_cell(design, cell, state, rnd);
+                // If valid, try and swap to a new position and see if
+                // the new position is valid/worthwhile
+                if (try_bel != BelId() && try_bel != cell->bel)
+                    try_swap_position(design, cell, try_bel, rnd, state);
+            }
+        }
+        // Heuristic to improve placement on the 8k
+        if (state.improved) {
+            n_no_progress = 0;
+            // std::cout << "improved\n";
+        } else
+            ++n_no_progress;
+
+        if (state.temp <= 1e-3 && n_no_progress >= 5)
+            break;
+
+        double Raccept = (double)state.n_accept / (double)state.n_move;
+
+        int M = std::max(max_x, max_y) + 1;
+
+        double upper = 0.6, lower = 0.4;
+
+        if (state.curr_wirelength < 0.95 * avg_wirelength)
+            avg_wirelength = 0.8 * avg_wirelength + 0.2 * state.curr_wirelength;
+        else {
+            if (Raccept >= 0.8) {
+                state.temp *= 0.7;
+            } else if (Raccept > upper) {
+                if (state.diameter < M)
+                    ++state.diameter;
+                else
+                    state.temp *= 0.9;
+            } else if (Raccept > lower) {
+                state.temp *= 0.95;
+            } else {
+                // Raccept < 0.3
+                if (state.diameter > 1)
+                    --state.diameter;
+                else
+                    state.temp *= 0.8;
+            }
+        }
+    }
+}
+
+NEXTPNR_NAMESPACE_END