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Diffstat (limited to 'ext/dsent/model/optical/OpticalLinkBackendTx.cc')
| -rw-r--r-- | ext/dsent/model/optical/OpticalLinkBackendTx.cc | 355 |
1 files changed, 355 insertions, 0 deletions
diff --git a/ext/dsent/model/optical/OpticalLinkBackendTx.cc b/ext/dsent/model/optical/OpticalLinkBackendTx.cc new file mode 100644 index 000000000..18d86cfe7 --- /dev/null +++ b/ext/dsent/model/optical/OpticalLinkBackendTx.cc @@ -0,0 +1,355 @@ +#include "model/optical/OpticalLinkBackendTx.h" + +#include "util/Constants.h" +#include "model/PortInfo.h" +#include "model/TransitionInfo.h" +#include "model/EventInfo.h" +#include "model/electrical/MuxTreeSerializer.h" +#include "model/electrical/BarrelShifter.h" +#include "model/electrical/Multiplexer.h" +#include <cmath> + +namespace DSENT +{ + // TODO: Kind of don't like the way thermal tuning is written here. Maybe will switch + // to curve fitting the CICC paper, which uses results from a monte-carlo sim + + OpticalLinkBackendTx::OpticalLinkBackendTx(const String& instance_name_, const TechModel* tech_model_) + : ElectricalModel(instance_name_, tech_model_) + { + initParameters(); + initProperties(); + } + + OpticalLinkBackendTx::~OpticalLinkBackendTx() + {} + + void OpticalLinkBackendTx::initParameters() + { + addParameterName("InBits"); + addParameterName("CoreDataRate"); + addParameterName("LinkDataRate"); + addParameterName("RingTuningMethod"); + addParameterName("BitDuplicate"); + return; + } + + void OpticalLinkBackendTx::initProperties() + { + return; + } + + void OpticalLinkBackendTx::constructModel() + { + unsigned int in_bits = getParameter("InBits"); + double core_data_rate = getParameter("CoreDataRate"); + double link_data_rate = getParameter("LinkDataRate"); + const String& tuning_method = getParameter("RingTuningMethod");; + bool bit_duplicate = getParameter("BitDuplicate"); + + // Calculate serialization ratio + unsigned int serialization_ratio = (unsigned int) floor(link_data_rate / core_data_rate); + ASSERT(serialization_ratio == link_data_rate / core_data_rate, + "[Error] " + getInstanceName() + " -> Cannot have non-integer serialization ratios " + + "(" + (String) (core_data_rate / link_data_rate) + ")!"); + + // Calculate output width + ASSERT(floor((double) in_bits / serialization_ratio) == (double) in_bits / serialization_ratio, + "[Error] " + getInstanceName() + " -> Input width (" + (String) in_bits + ") " + + "must be a multiple of the serialization ratio (" + (String) serialization_ratio + ")!"); + unsigned int out_bits = in_bits / serialization_ratio; + + getGenProperties()->set("SerializationRatio", serialization_ratio); + getGenProperties()->set("OutBits", out_bits); + + // Create ports + createInputPort("In", makeNetIndex(0, in_bits-1)); + createInputPort("LinkCK"); + createOutputPort("Out", makeNetIndex(0, out_bits-1)); + + //Create energy, power, and area results + createElectricalResults(); + // Create ring heating power cost + addNddPowerResult(new AtomicResult("RingTuning")); + // Create process bits event + createElectricalEventResult("ProcessBits"); + getEventInfo("ProcessBits")->setTransitionInfo("LinkCK", TransitionInfo(0.0, (double) serialization_ratio / 2.0, 0.0)); + // Set conditions during idle state + getEventInfo("Idle")->setStaticTransitionInfos(); + getEventInfo("Idle")->setTransitionInfo("LinkCK", TransitionInfo(0.0, (double) serialization_ratio / 2.0, 0.0)); + + // Create serializer + const String& serializer_name = "Serializer"; + MuxTreeSerializer* serializer = new MuxTreeSerializer(serializer_name, getTechModel()); + serializer->setParameter("InBits", in_bits); + serializer->setParameter("InDataRate", core_data_rate); + serializer->setParameter("OutDataRate", link_data_rate); + serializer->setParameter("BitDuplicate", bit_duplicate); + serializer->construct(); + + addSubInstances(serializer, 1.0); + addElectricalSubResults(serializer, 1.0); + getEventResult("ProcessBits")->addSubResult(serializer->getEventResult("Serialize"), serializer_name, 1.0); + + if ((tuning_method == "ThermalWithBitReshuffle") || (tuning_method == "ElectricalAssistWithBitReshuffle")) + { + // If a bit reshuffling backend is present, create the reshuffling backend + unsigned int reorder_degree = getBitReorderDegree(); + + // Create intermediate nets + createNet("SerializerIn", makeNetIndex(0, in_bits-1)); + createNet("ReorderIn", makeNetIndex(0, out_bits+reorder_degree-1)); + assign("ReorderIn", makeNetIndex(out_bits, out_bits+reorder_degree-1), "ReorderIn", makeNetIndex(0, reorder_degree-1)); + + // Create barrelshifter + unsigned int shift_index_min = (unsigned int)ceil(log2(serialization_ratio)); + unsigned int shift_index_max = std::max(shift_index_min, (unsigned int) ceil(log2(in_bits)) - 1); + + // Remember some things + getGenProperties()->set("ReorderDegree", reorder_degree); + getGenProperties()->set("ShiftIndexMin", shift_index_min); + getGenProperties()->set("ShiftIndexMax", shift_index_max); + + const String& barrel_shift_name = "BarrelShifter"; + BarrelShifter* barrel_shift = new BarrelShifter(barrel_shift_name, getTechModel()); + barrel_shift->setParameter("NumberBits", in_bits); + barrel_shift->setParameter("ShiftIndexMax", shift_index_max); + barrel_shift->setParameter("ShiftIndexMin", shift_index_min); + barrel_shift->setParameter("BitDuplicate", bit_duplicate); + barrel_shift->construct(); + + // Create bit reorder muxes + const String& reorder_mux_name = "ReorderMux"; + Multiplexer* reorder_mux = new Multiplexer(reorder_mux_name, getTechModel()); + reorder_mux->setParameter("NumberBits", out_bits); + reorder_mux->setParameter("NumberInputs", reorder_degree); + reorder_mux->setParameter("BitDuplicate", bit_duplicate); + reorder_mux->construct(); + + // Connect barrelshifter + // TODO: Connect barrelshift shifts! + portConnect(barrel_shift, "In", "In"); + portConnect(barrel_shift, "Out", "SerializerIn"); + + // Connect serializer + portConnect(serializer, "In", "SerializerIn"); + portConnect(serializer, "Out", "ReorderIn", makeNetIndex(0, out_bits-1)); + portConnect(serializer, "OutCK", "LinkCK"); + + // Connect bit reorder muxes + // TODO: Connect re-order multiplex select signals! + for (unsigned int i = 0; i < reorder_degree; i++) + portConnect(reorder_mux, "In" + (String) i, "ReorderIn", makeNetIndex(i, i+out_bits-1)); + portConnect(reorder_mux, "Out", "Out"); + + addSubInstances(barrel_shift, 1.0); + addSubInstances(reorder_mux, 1.0); + addElectricalSubResults(barrel_shift, 1.0); + addElectricalSubResults(reorder_mux, 1.0); + getEventResult("ProcessBits")->addSubResult(barrel_shift->getEventResult("BarrelShift"), barrel_shift_name, 1.0); + getEventResult("ProcessBits")->addSubResult(reorder_mux->getEventResult("Mux"), reorder_mux_name, 1.0); // This happens multiple times + } + else if ((tuning_method == "FullThermal") || (tuning_method == "AthermalWithTrim")) + { + // If no bit reshuffling backend is present, then just connect serializer up + portConnect(serializer, "In", "In"); + portConnect(serializer, "Out", "Out"); + portConnect(serializer, "OutCK", "LinkCK"); + } + else + { + ASSERT(false, "[Error] " + getInstanceName() + " -> Unknown ring tuning method '" + tuning_method + "'!"); + } + + return; + } + + void OpticalLinkBackendTx::updateModel() + { + // Update everyone + Model::updateModel(); + // Update ring tuning power + getNddPowerResult("RingTuning")->setValue(getRingTuningPower()); + return; + } + + void OpticalLinkBackendTx::propagateTransitionInfo() + { + // Get parameters + const String& tuning_method = getParameter("RingTuningMethod"); + + // Update the serializer + if ((tuning_method == "ThermalWithBitReshuffle") || (tuning_method == "ElectricalAssistWithBitReshuffle")) + { + // Get generated properties + unsigned int reorder_degree = getGenProperties()->get("ReorderDegree").toUInt(); + unsigned int shift_index_min = getGenProperties()->get("ShiftIndexMin").toUInt(); + unsigned int shift_index_max = getGenProperties()->get("ShiftIndexMax").toUInt(); + + // Update barrel shifter + const String& barrel_shift_name = "BarrelShifter"; + ElectricalModel* barrel_shift = (ElectricalModel*) getSubInstance(barrel_shift_name); + propagatePortTransitionInfo(barrel_shift, "In", "In"); + // Set shift transitions to be very low (since it is affected by slow temperature time constants) + for (unsigned int i = shift_index_min; i <= shift_index_max; ++i) + barrel_shift->getInputPort("Shift" + (String) i)->setTransitionInfo(TransitionInfo(0.499, 0.001, 0.499)); + barrel_shift->use(); + + // Set serializer transition info + ElectricalModel* serializer = (ElectricalModel*) getSubInstance("Serializer"); + propagatePortTransitionInfo(serializer, "In", barrel_shift, "Out"); + propagatePortTransitionInfo(serializer, "OutCK", "LinkCK"); + serializer->use(); + + // Reorder mux shift select bits + unsigned int reorder_sel_bits = (unsigned int)ceil(log2(reorder_degree)); + + // Reorder mux probabilities + const String& reorder_mux_name = "ReorderMux"; + ElectricalModel* reorder_mux = (ElectricalModel*) getSubInstance(reorder_mux_name); + for (unsigned int i = 0; i < reorder_degree; ++i) + propagatePortTransitionInfo(reorder_mux, "In" + (String) i, serializer, "Out"); + // Set select transitions to be 0, since these are statically configured + for (unsigned int i = 0; i < reorder_sel_bits; ++i) + reorder_mux->getInputPort("Sel" + (String) i)->setTransitionInfo(TransitionInfo(0.5, 0.0, 0.5)); + reorder_mux->use(); + + // Set output transition info + propagatePortTransitionInfo("Out", reorder_mux, "Out"); + } + else if ((tuning_method == "FullThermal") || (tuning_method == "AthermalWithTrim")) + { + // Set serializer transition info + ElectricalModel* serializer = (ElectricalModel*) getSubInstance("Serializer"); + propagatePortTransitionInfo(serializer, "In", "In"); + propagatePortTransitionInfo(serializer, "OutCK", "LinkCK"); + serializer->use(); + + // Set output transition info + propagatePortTransitionInfo("Out", serializer, "Out"); + } + + return; + } + + double OpticalLinkBackendTx::getRingTuningPower() + { + // Get properties + const String& tuning_method = getParameter("RingTuningMethod");; + unsigned int number_rings = getGenProperties()->get("OutBits"); + + // Get tech model parameters + double R = getTechModel()->get("Ring->Radius"); + double n_g = getTechModel()->get("Ring->GroupIndex"); + double heating_efficiency = getTechModel()->get("Ring->HeatingEfficiency"); + // This can actually be derived if we know thermo-optic coefficient (delta n / delta T) + double tuning_efficiency = getTechModel()->get("Ring->TuningEfficiency"); + double sigma_r_local = getTechModel()->get("Ring->LocalVariationSigma"); + double sigma_r_systematic = getTechModel()->get("Ring->SystematicVariationSigma"); + double T_max = getTechModel()->get("Ring->TemperatureMax"); + double T_min = getTechModel()->get("Ring->TemperatureMin"); + double T = getTechModel()->get("Temperature"); + + // Get constants + double c = Constants::c; + double pi = Constants::pi; + + double tuning_power = 0.0; + + if (tuning_method == "ThermalWithBitReshuffle") + { + // When an electrical backend is present, rings only have to tune to the nearest channel + // This can be approximated as each ring tuning to something exactly 1 channel away + + // Setup calculations + double L = 2 * pi * R; // Optical length + double FSR = c / (n_g * L); // Free spectral range + double freq_sep = FSR / number_rings; // Channel separation + + // Calculate tuning power + tuning_power = number_rings * freq_sep / (tuning_efficiency * heating_efficiency); + } + else if (tuning_method == "ElectricalAssistWithBitReshuffle") + { + // Electrical assistance allows for a fraction of the tuning range to be + // covered electrically. This is most pronounced when the tuning range is small, + // such is the case when bit reshuffling is applied. The electrically + // assisted part of it pretty much comes for free... + + // Get electrically tunable range + double max_assist = getTechModel()->get("Ring->MaxElectricallyTunableFreq"); + + // Setup calculations + double L = 2 * pi * R; // Optical length + double FSR = c / (n_g * L); // Free spectral range + double freq_sep = FSR / number_rings; // Channel separation + double heating_range = std::max(0.0, freq_sep - max_assist); // The distance needed to bridge using heaters + + // Calculate tuning power, which is really only the power spent on heating since + // distance tuned electrically is pretty much free + tuning_power = number_rings * heating_range / (tuning_efficiency * heating_efficiency); + } + else if (tuning_method == "FullThermal") + { + // If there is no bit reshuffling backend, each ring must tune to an + // absolute channel frequency. Since we can only heat rings (and not cool), + // we can only red-shift (decrease frequency). Thus, a fabrication bias + // must be applied such that under any process and temperature corner, the + // ring resonance remains above channel resonance + // I'll use 3 sigmas of sigma_r_local and sigma_r_systematic, and bias against + // the full temperature range + double fabrication_bias_freq = 3.0 * sqrt(pow(sigma_r_local, 2) + pow(sigma_r_systematic, 2)) + + (T_max - T_min) * tuning_efficiency; + + // The local/systematic variations are 0 on average. Thus, the tuning distance can be calculated as + double tuning_distance = fabrication_bias_freq - (T - T_min) * tuning_efficiency; + + // Tuning power needed is just the number of rings * tuning distance / (tuning and heating efficiencies) + tuning_power = number_rings * tuning_distance / (tuning_efficiency * heating_efficiency); + } + else if (tuning_method == "AthermalWithTrim") + { + // Athermal! Each ring's process variations are trimmed! Everything is free! + // Basically an ideal scenario + tuning_power = 0; + } + else + { + ASSERT(false, "[Error] " + getInstanceName() + " -> Unknown ring tuning method '" + tuning_method + "'!"); + } + + return tuning_power; + } + + unsigned int OpticalLinkBackendTx::getBitReorderDegree() + { + // Get properties + unsigned int number_rings = getGenProperties()->get("OutBits"); + + // Get tech model parameters + double R = getTechModel()->get("Ring->Radius"); + double n_g = getTechModel()->get("Ring->GroupIndex"); + // This can actually be derived if we know thermo-optic coefficient (delta n / delta T) + double sigma_r_local = getTechModel()->get("Ring->LocalVariationSigma"); + + // Get constants + double c = Constants::c; + double pi = Constants::pi; + + // Calculates the degree of bit re-order multiplexing needed for bit-reshuffling backend + // Bit reshuffling tuning is largely unaffected by sigma_r_systematic. However, sigma_r_local + // Can potentially throw each ring to a channel several channels away. This just calculates + // the degree of bit reorder muxing needed to realign bits in the correct order + + // Setup calculations + double L = 2 * pi * R; // Optical length + double FSR = c / (n_g * L); // Free spectral range + double freq_sep = FSR / number_rings; // Channel separation + // Using 4 sigmas as the worst re-ordering case (must double to get both sides) + unsigned int worst_case_channels = (unsigned int)ceil(2.0 * 4.0 * sigma_r_local / freq_sep); + + return worst_case_channels; + } + +} // namespace DSENT + |