ConnectionSweeper.cc

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/*
    Copyright (c) 2002-2011 Tampere University.
 
    This file is part of TTA-Based Codesign Environment (TCE).
 
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/**
 * @file ConnectionSweeper.cc
 *
 * Explorer plugin that optimizes the interconnection network by
 * removing connections with least effect to the cycle count.
 *
 * @author Pekka Jääskeläinen 2011
 * @note rating: red
 */
 
#include <vector>
#include <string>
#include <set>
#include <memory>
 
#include "DesignSpaceExplorerPlugin.hh"
#include "MachineConnectivityCheck.hh"
#include "DSDBManager.hh"
#include "Machine.hh"
#include "Connection.hh"
#include "TestApplication.hh"
#include "Program.hh"
#include "Instruction.hh"
#include "Move.hh"
#include "Port.hh"
#include "FUPort.hh"
#include "Socket.hh"
#include "Terminal.hh"
#include "Terminal.hh"
#include "HDBRegistry.hh"
#include "ICDecoderEstimatorPlugin.hh"
#include "ControlUnit.hh"
#include "HWOperation.hh"
#include "StringTools.hh"
#include "Segment.hh"
#include "CostEstimates.hh"
#include "Application.hh"
#include "Exception.hh"
#include "Procedure.hh"
 
#include "LLVMBackend.hh"
#include "RegisterQuantityCheck.hh"
 
#include "MinimalOpSetCheck.hh"
#include "MachineCheckResults.hh"
 
#include "tce_config.h"
 
using namespace TTAProgram;
using namespace TTAMachine;
using namespace HDB;
using std::endl;
 
/**
 * Explorer plugin that optimizes the interconnection network by
 * removing connections with least effect to the cycle count first.
 *
 * 1) Sweeps through the buses in order. 
 * 2) For each bus, tries to remove each connection one-by-one,
 *    and evaluates the effect to the cycle count. The one with
 *    the least effect is removed first. The process is repeated
 *    until the minimum cycle count increase crosses an user-defined
 *    threshold, or the program becomes unschedulable.
 *    Emphasize RF port connections as they tend to get to the longest
 *    path due to the register selection logic being in the same path.
 * 3) After that, the next bus is tried similarly, until either all
 *    the buses have been optimized this way.
 * 4) The DSDB can be queried with the connection count as the first measure,
 *    the cycle count the second with both as small as possible.
 *
 */
class ConnectionSweeper : public DesignSpaceExplorerPlugin {
    PLUGIN_DESCRIPTION(
        "Optimizes the IC of the given configuration by removing bus "
        "connections with least effect to the cycle count first.");
 
    ConnectionSweeper() : DesignSpaceExplorerPlugin() {
 
        addParameter(ccWorseningThresholdPN_, UINT, false, "50",
                     "Limit the reduction when the cycle count "
                     "drops more than this limit (%).");
        addParameter(allOrNothingPN_, BOOL, false, "true",
                     "Do not consider single connections. Just try to remove "
                     "all of the bypass or RF connections at once. If fails, "
                     "leave them all. Leads quicker to symmetric reduced "
                     "connectivity machines.");
    }
 
    virtual bool requiresStartingPointArchitecture() const { return true; }
    virtual bool producesArchitecture() const { return true; }
    virtual bool requiresHDB() const { return false; }
    virtual bool requiresSimulationData() const { return true; }
    
    virtual std::vector<RowID>
    explore(const RowID& startPointConfigurationID, const unsigned int&) {
 
 
        readParameters();
        
        DSDBManager& dsdb = db();
        DSDBManager::MachineConfiguration startConf = 
            dsdb.configuration(startPointConfigurationID);
            
        // loads starting configuration
        Machine* origMach = NULL;
        origMach = dsdb.architecture(startConf.architectureID);
        // get cycle counts for the original architecture for each app
        std::set<RowID> appIds = dsdb.applicationIDs();
        for (std::set<RowID>::const_iterator appI = appIds.begin(); 
             appI != appIds.end(); ++appI) {
            RowID appID = *appI;
            if (!dsdb.hasCycleCount(appID, startConf.architectureID)) {
                CostEstimates estimates;
                bool success = evaluate(startConf, estimates, false);
                if (!success) {
                    throw Exception(
                        __FILE__, __LINE__, __func__,
                        "Could not evaluate the starting point arch.");
                }
            }
            assert(dsdb.hasCycleCount(appID, startConf.architectureID));
            origCycles_[appID] = 
                dsdb.cycleCount(appID, startConf.architectureID);
            TCEString s;
            s << "app: " << appID << " original cycles: "; 
            s << origCycles_[appID] << " total connections: "
              << MachineConnectivityCheck::totalConnectionCount(*origMach);
            verboseLog(s);                   
        }
 
        std::vector<RowID> result;
 
        // sweep through the buses, the register file connections first
        // start from the biggest allowed worsening threshold to find
        // the machines with minimal connections first
        const int thresholdStep = 
            std::max(maxCcWorseningThreshold_ / 4, (unsigned)1);
        for (ccWorseningThreshold_ = maxCcWorseningThreshold_;
             ccWorseningThreshold_ > 0;
             ccWorseningThreshold_ = 
                 std::max(0, (int)ccWorseningThreshold_ - thresholdStep)) {
            TCEString s;
            s << "### Testing max worsening threshold "
              << ccWorseningThreshold_ << "% of "
              << maxCcWorseningThreshold_ << "%";
            verboseLog(s);
 
            s = "### Reducing register file and immediate unit connections.";
            verboseLog(s);
            std::list<RowID> rfSweepResults = 
                sweepRFs(startPointConfigurationID);
 
            if (rfSweepResults.size() == 0) break;
 
            RowID bestFromRFSweep = rfSweepResults.front();
            result.insert(result.begin(), bestFromRFSweep);
 
            s = "### Reducing bypass connections.";
            verboseLog(s);
 
            std::list<RowID> bypassSweepResults = 
                sweepBypasses(bestFromRFSweep);
            if (bypassSweepResults.size() == 0) break;
 
            RowID bestFromBPSweep = rfSweepResults.front();
            result.insert(result.begin(), bestFromBPSweep);
        }
        return result;
    }
 
    /**
     * Sweeps the register file and immediate unit connections.
     */
    std::list<RowID>
    sweepRFs(RowID startPointConfigurationID) {
 
        DSDBManager::MachineConfiguration startConf = 
            db().configuration(startPointConfigurationID);
            
        // loads starting configuration
        Machine* mach = db().architecture(startConf.architectureID);
        DSDBManager::MachineConfiguration bestConf = startConf;
 
 
        std::list<RowID> result;
        for (int busI = 0; busI < mach->busNavigator().count();
             ++busI) {
            const TTAMachine::Bus& bus = *mach->busNavigator().item(busI);
            
            verboseLog(TCEString("considering bus ") + bus.name());
 
            std::vector<const TTAMachine::Connection*> connections;         
            const TTAMachine::Segment& seg = *bus.segment(0);
            for (int rfI = 0; rfI < mach->registerFileNavigator().count();
                 ++rfI) {
                const TTAMachine::RegisterFile& rf = 
                    *mach->registerFileNavigator().item(rfI);
                for (int connI = 0; connI < seg.connectionCount();
                     ++connI) {
                    const TTAMachine::Connection& conn = 
                        seg.connection(*seg.connection(connI));
                    for (int portI = 0; portI < conn.socket()->portCount(); 
                         ++portI) {
                        const TTAMachine::Port& port = 
                            *conn.socket()->port(portI);
                        if (port.parentUnit() == &rf) {
                            connections.push_back(&conn);
                        }
                    }
                }
            }
            for (int iuI = 0; iuI < mach->immediateUnitNavigator().count();
                 ++iuI) {
                const TTAMachine::ImmediateUnit& iu = 
                    *mach->immediateUnitNavigator().item(iuI);
                for (int connI = 0; connI < seg.connectionCount();
                     ++connI) {
                    const TTAMachine::Connection& conn = 
                        seg.connection(*seg.connection(connI));
                    for (int portI = 0; portI < conn.socket()->portCount(); 
                         ++portI) {
                        const TTAMachine::Port& port = 
                            *conn.socket()->port(portI);
                        if (port.parentUnit() == &iu) {
                            connections.push_back(&conn);
                        }
                    }
                }
            }
 
            std::list<RowID> newConfs = removeAllConnections(connections, bestConf);
 
            if (!allOrNothing_ && newConfs.size() == 0) {
                verboseLog("trying the connections one-by-one\n");
                removeLeastNecessaryConnections(connections, bestConf);
            }
 
            if (newConfs.size() > 0) {
                bestConf = db().configuration(newConfs.front());
                for (std::list<RowID>::reverse_iterator i = newConfs.rbegin();
                     i != newConfs.rend(); ++i) {
                    result.insert(result.begin(), *i);
                }
            }
        }
        return result;
    }
 
    /**
     * Sweeps the bypass connections, that is, everything else but the
     * register file and immediate unit connections.
     */
    std::list<RowID>
    sweepBypasses(RowID startPointConfigurationID) {
 
        DSDBManager::MachineConfiguration startConf = 
            db().configuration(startPointConfigurationID);
            
        // loads starting configuration
        Machine* mach = db().architecture(startConf.architectureID);
        DSDBManager::MachineConfiguration bestConf = startConf;
 
        std::list<RowID> result;
        for (int busI = 0; busI < mach->busNavigator().count();
             ++busI) {
            const TTAMachine::Bus& bus = *mach->busNavigator().item(busI);
            
            verboseLog(TCEString("considering bus ") + bus.name());
 
            std::vector<const TTAMachine::Connection*> connections;         
            const TTAMachine::Segment& seg = *bus.segment(0);
            for (int connI = 0; connI < seg.connectionCount();
                 ++connI) {
                const TTAMachine::Connection& conn = 
                    seg.connection(*seg.connection(connI));
                // check if the connection is to an IU or RF
                bool rfConnection = false;
                for (int rfI = 0; rfI < mach->registerFileNavigator().count();
                     ++rfI) {
                    const TTAMachine::RegisterFile& rf = 
                        *mach->registerFileNavigator().item(rfI);
                    for (int portI = 0; portI < conn.socket()->portCount(); 
                         ++portI) {
                        const TTAMachine::Port& port = 
                            *conn.socket()->port(portI);
                        if (port.parentUnit() == &rf) {
                            rfConnection = true;
                            break;
                        }
                    }
                    
                }
                for (int iuI = 0; 
                     !rfConnection && 
                         iuI < mach->immediateUnitNavigator().count();
                     ++iuI) {
                    const TTAMachine::ImmediateUnit& iu = 
                        *mach->immediateUnitNavigator().item(iuI);
                    for (int portI = 0; portI < conn.socket()->portCount(); 
                         ++portI) {
                        const TTAMachine::Port& port = 
                            *conn.socket()->port(portI);
                        if (port.parentUnit() == &iu) {
                            rfConnection = true;
                            break;
                        }
                    }
                }
                if (!rfConnection) connections.push_back(&conn);
            }
 
 
            std::list<RowID> newConfs = removeAllConnections(connections, bestConf);
 
            if (!allOrNothing_ && newConfs.size() == 0) {
                verboseLog("trying the connections one-by-one\n");
                removeLeastNecessaryConnections(connections, bestConf);
            }
 
            if (newConfs.size() > 0) {
                bestConf = db().configuration(newConfs.front());
                for (std::list<RowID>::reverse_iterator i = newConfs.rbegin();
                     i != newConfs.rend(); ++i) {
                    result.insert(result.begin(), *i);
                }
            }
        }
        return result;
    }
 
 
private:
    // cycle counts for the original architecture for each app
    // RowID == application ID
    std::map<RowID, ClockCycleCount> origCycles_;
    // parameter name variables
    static const std::string ccWorseningThresholdPN_;
    static const std::string allOrNothingPN_;
    // the max cycle count worsening threshold in percentages in comparison to
    // the fully connected architecture
    unsigned int maxCcWorseningThreshold_;
    // the current threshold
    unsigned int ccWorseningThreshold_;
    // from the set of connections, tries to remove all of them or none
    // should lead to quick results with relatively symmetric connectivity
    // machines
    bool allOrNothing_;
    /**
     * Reads the parameters given to the plugin.
     */
    void readParameters() {
        readOptionalParameter(
            ccWorseningThresholdPN_, maxCcWorseningThreshold_);
        readOptionalParameter(
            allOrNothingPN_, allOrNothing_);
    }
    
    /**
     * Computes the average cycle count worsening for the given processor
     * configuration across all the explored applications.
     */
    float 
    averageWorsening(RowID confId) {
        float worsenings = 0.0f;
        std::set<RowID> appIds = db().applicationIDs();
        for (std::set<RowID>::const_iterator appI = appIds.begin(); 
             appI != appIds.end(); ++appI) {
            RowID appID = *appI;
            DSDBManager::MachineConfiguration conf = 
                db().configuration(confId);
            if (!db().hasCycleCount(appID, conf.architectureID)) {
                continue; /* the evaluation had failed */
            }
            int origCycles = origCycles_[appID];
            int newCycles = 
                db().cycleCount(appID, conf.architectureID);
            worsenings += 100.0*(newCycles - origCycles) / origCycles;
        }
        float avgWorsening = worsenings / appIds.size();
        return avgWorsening;
    }
 
 
    std::list<RowID>
    removeAllConnections(
        std::vector<const TTAMachine::Connection*> connections,
        const DSDBManager::MachineConfiguration& startConf) {
 
        std::list<RowID> results;
 
#if (!defined(HAVE_CXX11) && !defined(HAVE_CXX0X))
        std::auto_ptr<TTAMachine::Machine> currentMachine(
            db().architecture(startConf.architectureID));
#else
        std::unique_ptr<TTAMachine::Machine> currentMachine(
            db().architecture(startConf.architectureID));
#endif
        
        for (std::vector<const TTAMachine::Connection*>::iterator 
                 connI = connections.begin(); connI != connections.end();
             ++connI) {
            const TTAMachine::Connection* conn = *connI;
            removeConnection(*currentMachine, *conn);
        }
 
        DSDBManager::MachineConfiguration conf;
        conf.architectureID = db().addArchitecture(*currentMachine);
        RowID confId = db().addConfiguration(conf);
        conf = db().configuration(confId);
        CostEstimates estimates;
        bool success = evaluate(conf, estimates, false);
        float worsening = averageWorsening(confId);
        if (success) {
#if (!defined(HAVE_CXX11) && !defined(HAVE_CXX0X))
            std::auto_ptr<TTAMachine::Machine> arch
                (db().architecture(
                    db().configuration(confId).architectureID));
#else
            std::unique_ptr<TTAMachine::Machine> arch
                (db().architecture(
                    db().configuration(confId).architectureID));
#endif
 
            
            if (worsening <= ccWorseningThreshold_) {
                results.push_back(confId);
                TCEString s;
                s << "removing all connections was within threshold: #" 
                  << confId << " avg worsening: ";
                s << (int)worsening << "% " << " total connections: "
                  << MachineConnectivityCheck::totalConnectionCount(*arch);
                verboseLog(s);
            } else {
                TCEString s;
                s << "removing all connections was not within the "
                  << "threshold: #" 
                  << confId << " avg worsening: ";
                s << (int)worsening << "% " << " total connections: "
                  << MachineConnectivityCheck::totalConnectionCount(*arch);
                s << "\n";
                verboseLog(s);                    
            }
        } else {
            TCEString s;
            s << "removing all connections led to unschedulable program\n";
            verboseLog(s);
        }
        return results;
    }
 
    /**
     * Removes the connections in the given set that affect the cycle count
     * the least until the worsening threshold is reached or in case the
     * program becomes uncompilable.
     *
     * @param tryAllFirst Tries to remove all connections first and if it
     * the results fits in the cc threshold, does not try configuration with
     * the listed connections.
     */ 
    std::list<RowID>
    removeLeastNecessaryConnections(
        std::vector<const TTAMachine::Connection*> connections,
        const DSDBManager::MachineConfiguration& startConf) {
 
        std::list<RowID> results;
        DSDBManager::MachineConfiguration bestConf = startConf;
 
        bool couldRemove = true;
        while (couldRemove) {
            couldRemove = false;
            const TTAMachine::Connection* mostUnneededConn = NULL;
            float bestAvgccWorsening = 100.0;
            TTAMachine::Machine* currentMachine = 
                db().architecture(bestConf.architectureID);
            RowID bestConfInThisIteration = -1;
            std::vector<const TTAMachine::Connection*>::iterator unneededPos = 
                connections.end();
            // find the least affecting connection removal for this stage
            for (std::vector<const TTAMachine::Connection*>::iterator 
                     connI = connections.begin(); connI != connections.end();
                 ++connI) {
                const TTAMachine::Connection* conn = *connI;
 
                // compute the avgccWorsening
                // check if it's the best found and if it's above the
                // threshold               
                TTAMachine::Machine mach = *currentMachine;
                removeConnection(mach, *conn);
 
                DSDBManager::MachineConfiguration conf;
                conf.architectureID = db().addArchitecture(mach);
                RowID confId = db().addConfiguration(conf);
                bool success = evaluate(db().configuration(confId));
 
                if (success) {
                    unsigned int avgWorsening = 
                        (unsigned)averageWorsening(confId);
                    if (avgWorsening <= ccWorseningThreshold_ &&
                        avgWorsening < bestAvgccWorsening) {
                        mostUnneededConn = conn;
                        bestConfInThisIteration = confId;
                        unneededPos = connI;
                        bestAvgccWorsening = avgWorsening;
                        TCEString s;
                        s << "new config: #" << bestConfInThisIteration 
                          << " avg worsening: ";
                        s << (int)bestAvgccWorsening << "% " 
                          << " total connections: "
                          << MachineConnectivityCheck::totalConnectionCount(
                              *db().architecture(
                                  db().configuration(confId).architectureID));
                        verboseLog(s);
                    }
                } else {
                    TCEString s;
                    s << "new config: #" << confId << " is unschedulable";
                    verboseLog(s);
                }
            }
            if (mostUnneededConn != NULL) {
                // more connections we remove while staying in the threshold, 
                // better the processor gets
                bestConf = db().configuration(bestConfInThisIteration);
                couldRemove = true;
                connections.erase(unneededPos);
                results.push_front(bestConfInThisIteration);
                TCEString s;
                s << "best config from this bus sweep: #" 
                  << bestConfInThisIteration << " avg worsening: ";
                s << (int)bestAvgccWorsening << "% " << " total connections: "
                  << MachineConnectivityCheck::totalConnectionCount(
                      *db().architecture(bestConf.architectureID));
                verboseLog(s);
            }
        }
        return results;
    }
 
    void
    removeConnection(
        TTAMachine::Machine& mach, const TTAMachine::Connection& connection) {
        TTAMachine::Segment& segment = 
            *mach.busNavigator().item(connection.bus()->parentBus()->name())->
            segment(0);
 
        TTAMachine::Socket& socket = 
            *mach.socketNavigator().item(connection.socket()->name());
 
        segment.detachSocket(socket);
    }
};
 
// parameter names
const std::string 
ConnectionSweeper::ccWorseningThresholdPN_("cc_worsening_threshold");
const std::string 
ConnectionSweeper::allOrNothingPN_("all_or_nothing_mode");
 
 
EXPORT_DESIGN_SPACE_EXPLORER_PLUGIN(ConnectionSweeper)