1/* Copyright (c) 2012 Massachusetts Institute of Technology
2 *
3 * Permission is hereby granted, free of charge, to any person obtaining a copy
4 * of this software and associated documentation files (the "Software"), to deal
5 * in the Software without restriction, including without limitation the rights
6 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
7 * copies of the Software, and to permit persons to whom the Software is
8 * furnished to do so, subject to the following conditions:
9 *
10 * The above copyright notice and this permission notice shall be included in
11 * all copies or substantial portions of the Software.
12 *
13 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
14 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
15 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
16 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
17 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
18 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
19 * THE SOFTWARE.
20 */
21 |
22#include "model/optical/OpticalLinkBackendTx.h"
23
24#include "util/Constants.h"
25#include "model/PortInfo.h"
26#include "model/TransitionInfo.h"
27#include "model/EventInfo.h"
28#include "model/electrical/MuxTreeSerializer.h"
29#include "model/electrical/BarrelShifter.h"
30#include "model/electrical/Multiplexer.h"
31#include <cmath>
32
33namespace DSENT
34{
35 // TODO: Kind of don't like the way thermal tuning is written here. Maybe will switch
36 // to curve fitting the CICC paper, which uses results from a monte-carlo sim
37
38 OpticalLinkBackendTx::OpticalLinkBackendTx(const String& instance_name_, const TechModel* tech_model_)
39 : ElectricalModel(instance_name_, tech_model_)
40 {
41 initParameters();
42 initProperties();
43 }
44
45 OpticalLinkBackendTx::~OpticalLinkBackendTx()
46 {}
47
48 void OpticalLinkBackendTx::initParameters()
49 {
50 addParameterName("InBits");
51 addParameterName("CoreDataRate");
52 addParameterName("LinkDataRate");
53 addParameterName("RingTuningMethod");
54 addParameterName("BitDuplicate");
55 return;
56 }
57
58 void OpticalLinkBackendTx::initProperties()
59 {
60 return;
61 }
62
63 void OpticalLinkBackendTx::constructModel()
64 {
65 unsigned int in_bits = getParameter("InBits");
66 double core_data_rate = getParameter("CoreDataRate");
67 double link_data_rate = getParameter("LinkDataRate");
68 const String& tuning_method = getParameter("RingTuningMethod");;
69 bool bit_duplicate = getParameter("BitDuplicate");
70
71 // Calculate serialization ratio
72 unsigned int serialization_ratio = (unsigned int) floor(link_data_rate / core_data_rate);
73 ASSERT(serialization_ratio == link_data_rate / core_data_rate,
74 "[Error] " + getInstanceName() + " -> Cannot have non-integer serialization ratios " +
75 "(" + (String) (core_data_rate / link_data_rate) + ")!");
76
77 // Calculate output width
78 ASSERT(floor((double) in_bits / serialization_ratio) == (double) in_bits / serialization_ratio,
79 "[Error] " + getInstanceName() + " -> Input width (" + (String) in_bits + ") " +
80 "must be a multiple of the serialization ratio (" + (String) serialization_ratio + ")!");
81 unsigned int out_bits = in_bits / serialization_ratio;
82
83 getGenProperties()->set("SerializationRatio", serialization_ratio);
84 getGenProperties()->set("OutBits", out_bits);
85
86 // Create ports
87 createInputPort("In", makeNetIndex(0, in_bits-1));
88 createInputPort("LinkCK");
89 createOutputPort("Out", makeNetIndex(0, out_bits-1));
90
91 //Create energy, power, and area results
92 createElectricalResults();
93 // Create ring heating power cost
94 addNddPowerResult(new AtomicResult("RingTuning"));
95 // Create process bits event
96 createElectricalEventResult("ProcessBits");
97 getEventInfo("ProcessBits")->setTransitionInfo("LinkCK", TransitionInfo(0.0, (double) serialization_ratio / 2.0, 0.0));
98 // Set conditions during idle state
99 getEventInfo("Idle")->setStaticTransitionInfos();
100 getEventInfo("Idle")->setTransitionInfo("LinkCK", TransitionInfo(0.0, (double) serialization_ratio / 2.0, 0.0));
101
102 // Create serializer
103 const String& serializer_name = "Serializer";
104 MuxTreeSerializer* serializer = new MuxTreeSerializer(serializer_name, getTechModel());
105 serializer->setParameter("InBits", in_bits);
106 serializer->setParameter("InDataRate", core_data_rate);
107 serializer->setParameter("OutDataRate", link_data_rate);
108 serializer->setParameter("BitDuplicate", bit_duplicate);
109 serializer->construct();
110
111 addSubInstances(serializer, 1.0);
112 addElectricalSubResults(serializer, 1.0);
113 getEventResult("ProcessBits")->addSubResult(serializer->getEventResult("Serialize"), serializer_name, 1.0);
114
115 if ((tuning_method == "ThermalWithBitReshuffle") || (tuning_method == "ElectricalAssistWithBitReshuffle"))
116 {
117 // If a bit reshuffling backend is present, create the reshuffling backend
118 unsigned int reorder_degree = getBitReorderDegree();
119
120 // Create intermediate nets
121 createNet("SerializerIn", makeNetIndex(0, in_bits-1));
122 createNet("ReorderIn", makeNetIndex(0, out_bits+reorder_degree-1));
123 assign("ReorderIn", makeNetIndex(out_bits, out_bits+reorder_degree-1), "ReorderIn", makeNetIndex(0, reorder_degree-1));
124
125 // Create barrelshifter
126 unsigned int shift_index_min = (unsigned int)ceil(log2(serialization_ratio));
127 unsigned int shift_index_max = std::max(shift_index_min, (unsigned int) ceil(log2(in_bits)) - 1);
128
129 // Remember some things
130 getGenProperties()->set("ReorderDegree", reorder_degree);
131 getGenProperties()->set("ShiftIndexMin", shift_index_min);
132 getGenProperties()->set("ShiftIndexMax", shift_index_max);
133
134 const String& barrel_shift_name = "BarrelShifter";
135 BarrelShifter* barrel_shift = new BarrelShifter(barrel_shift_name, getTechModel());
136 barrel_shift->setParameter("NumberBits", in_bits);
137 barrel_shift->setParameter("ShiftIndexMax", shift_index_max);
138 barrel_shift->setParameter("ShiftIndexMin", shift_index_min);
139 barrel_shift->setParameter("BitDuplicate", bit_duplicate);
140 barrel_shift->construct();
141
142 // Create bit reorder muxes
143 const String& reorder_mux_name = "ReorderMux";
144 Multiplexer* reorder_mux = new Multiplexer(reorder_mux_name, getTechModel());
145 reorder_mux->setParameter("NumberBits", out_bits);
146 reorder_mux->setParameter("NumberInputs", reorder_degree);
147 reorder_mux->setParameter("BitDuplicate", bit_duplicate);
148 reorder_mux->construct();
149
150 // Connect barrelshifter
151 // TODO: Connect barrelshift shifts!
152 portConnect(barrel_shift, "In", "In");
153 portConnect(barrel_shift, "Out", "SerializerIn");
154
155 // Connect serializer
156 portConnect(serializer, "In", "SerializerIn");
157 portConnect(serializer, "Out", "ReorderIn", makeNetIndex(0, out_bits-1));
158 portConnect(serializer, "OutCK", "LinkCK");
159
160 // Connect bit reorder muxes
161 // TODO: Connect re-order multiplex select signals!
162 for (unsigned int i = 0; i < reorder_degree; i++)
163 portConnect(reorder_mux, "In" + (String) i, "ReorderIn", makeNetIndex(i, i+out_bits-1));
164 portConnect(reorder_mux, "Out", "Out");
165
166 addSubInstances(barrel_shift, 1.0);
167 addSubInstances(reorder_mux, 1.0);
168 addElectricalSubResults(barrel_shift, 1.0);
169 addElectricalSubResults(reorder_mux, 1.0);
170 getEventResult("ProcessBits")->addSubResult(barrel_shift->getEventResult("BarrelShift"), barrel_shift_name, 1.0);
171 getEventResult("ProcessBits")->addSubResult(reorder_mux->getEventResult("Mux"), reorder_mux_name, 1.0); // This happens multiple times
172 }
173 else if ((tuning_method == "FullThermal") || (tuning_method == "AthermalWithTrim"))
174 {
175 // If no bit reshuffling backend is present, then just connect serializer up
176 portConnect(serializer, "In", "In");
177 portConnect(serializer, "Out", "Out");
178 portConnect(serializer, "OutCK", "LinkCK");
179 }
180 else
181 {
182 ASSERT(false, "[Error] " + getInstanceName() + " -> Unknown ring tuning method '" + tuning_method + "'!");
183 }
184
185 return;
186 }
187
188 void OpticalLinkBackendTx::updateModel()
189 {
190 // Update everyone
191 Model::updateModel();
192 // Update ring tuning power
193 getNddPowerResult("RingTuning")->setValue(getRingTuningPower());
194 return;
195 }
196
197 void OpticalLinkBackendTx::propagateTransitionInfo()
198 {
199 // Get parameters
200 const String& tuning_method = getParameter("RingTuningMethod");
201
202 // Update the serializer
203 if ((tuning_method == "ThermalWithBitReshuffle") || (tuning_method == "ElectricalAssistWithBitReshuffle"))
204 {
205 // Get generated properties
206 unsigned int reorder_degree = getGenProperties()->get("ReorderDegree").toUInt();
207 unsigned int shift_index_min = getGenProperties()->get("ShiftIndexMin").toUInt();
208 unsigned int shift_index_max = getGenProperties()->get("ShiftIndexMax").toUInt();
209
210 // Update barrel shifter
211 const String& barrel_shift_name = "BarrelShifter";
212 ElectricalModel* barrel_shift = (ElectricalModel*) getSubInstance(barrel_shift_name);
213 propagatePortTransitionInfo(barrel_shift, "In", "In");
214 // Set shift transitions to be very low (since it is affected by slow temperature time constants)
215 for (unsigned int i = shift_index_min; i <= shift_index_max; ++i)
216 barrel_shift->getInputPort("Shift" + (String) i)->setTransitionInfo(TransitionInfo(0.499, 0.001, 0.499));
217 barrel_shift->use();
218
219 // Set serializer transition info
220 ElectricalModel* serializer = (ElectricalModel*) getSubInstance("Serializer");
221 propagatePortTransitionInfo(serializer, "In", barrel_shift, "Out");
222 propagatePortTransitionInfo(serializer, "OutCK", "LinkCK");
223 serializer->use();
224
225 // Reorder mux shift select bits
226 unsigned int reorder_sel_bits = (unsigned int)ceil(log2(reorder_degree));
227
228 // Reorder mux probabilities
229 const String& reorder_mux_name = "ReorderMux";
230 ElectricalModel* reorder_mux = (ElectricalModel*) getSubInstance(reorder_mux_name);
231 for (unsigned int i = 0; i < reorder_degree; ++i)
232 propagatePortTransitionInfo(reorder_mux, "In" + (String) i, serializer, "Out");
233 // Set select transitions to be 0, since these are statically configured
234 for (unsigned int i = 0; i < reorder_sel_bits; ++i)
235 reorder_mux->getInputPort("Sel" + (String) i)->setTransitionInfo(TransitionInfo(0.5, 0.0, 0.5));
236 reorder_mux->use();
237
238 // Set output transition info
239 propagatePortTransitionInfo("Out", reorder_mux, "Out");
240 }
241 else if ((tuning_method == "FullThermal") || (tuning_method == "AthermalWithTrim"))
242 {
243 // Set serializer transition info
244 ElectricalModel* serializer = (ElectricalModel*) getSubInstance("Serializer");
245 propagatePortTransitionInfo(serializer, "In", "In");
246 propagatePortTransitionInfo(serializer, "OutCK", "LinkCK");
247 serializer->use();
248
249 // Set output transition info
250 propagatePortTransitionInfo("Out", serializer, "Out");
251 }
252
253 return;
254 }
255
256 double OpticalLinkBackendTx::getRingTuningPower()
257 {
258 // Get properties
259 const String& tuning_method = getParameter("RingTuningMethod");;
260 unsigned int number_rings = getGenProperties()->get("OutBits");
261
262 // Get tech model parameters
263 double R = getTechModel()->get("Ring->Radius");
264 double n_g = getTechModel()->get("Ring->GroupIndex");
265 double heating_efficiency = getTechModel()->get("Ring->HeatingEfficiency");
266 // This can actually be derived if we know thermo-optic coefficient (delta n / delta T)
267 double tuning_efficiency = getTechModel()->get("Ring->TuningEfficiency");
268 double sigma_r_local = getTechModel()->get("Ring->LocalVariationSigma");
269 double sigma_r_systematic = getTechModel()->get("Ring->SystematicVariationSigma");
270 double T_max = getTechModel()->get("Ring->TemperatureMax");
271 double T_min = getTechModel()->get("Ring->TemperatureMin");
272 double T = getTechModel()->get("Temperature");
273
274 // Get constants
275 double c = Constants::c;
276 double pi = Constants::pi;
277
278 double tuning_power = 0.0;
279
280 if (tuning_method == "ThermalWithBitReshuffle")
281 {
282 // When an electrical backend is present, rings only have to tune to the nearest channel
283 // This can be approximated as each ring tuning to something exactly 1 channel away
284
285 // Setup calculations
286 double L = 2 * pi * R; // Optical length
287 double FSR = c / (n_g * L); // Free spectral range
288 double freq_sep = FSR / number_rings; // Channel separation
289
290 // Calculate tuning power
291 tuning_power = number_rings * freq_sep / (tuning_efficiency * heating_efficiency);
292 }
293 else if (tuning_method == "ElectricalAssistWithBitReshuffle")
294 {
295 // Electrical assistance allows for a fraction of the tuning range to be
296 // covered electrically. This is most pronounced when the tuning range is small,
297 // such is the case when bit reshuffling is applied. The electrically
298 // assisted part of it pretty much comes for free...
299
300 // Get electrically tunable range
301 double max_assist = getTechModel()->get("Ring->MaxElectricallyTunableFreq");
302
303 // Setup calculations
304 double L = 2 * pi * R; // Optical length
305 double FSR = c / (n_g * L); // Free spectral range
306 double freq_sep = FSR / number_rings; // Channel separation
307 double heating_range = std::max(0.0, freq_sep - max_assist); // The distance needed to bridge using heaters
308
309 // Calculate tuning power, which is really only the power spent on heating since
310 // distance tuned electrically is pretty much free
311 tuning_power = number_rings * heating_range / (tuning_efficiency * heating_efficiency);
312 }
313 else if (tuning_method == "FullThermal")
314 {
315 // If there is no bit reshuffling backend, each ring must tune to an
316 // absolute channel frequency. Since we can only heat rings (and not cool),
317 // we can only red-shift (decrease frequency). Thus, a fabrication bias
318 // must be applied such that under any process and temperature corner, the
319 // ring resonance remains above channel resonance
320 // I'll use 3 sigmas of sigma_r_local and sigma_r_systematic, and bias against
321 // the full temperature range
322 double fabrication_bias_freq = 3.0 * sqrt(pow(sigma_r_local, 2) + pow(sigma_r_systematic, 2)) +
323 (T_max - T_min) * tuning_efficiency;
324
325 // The local/systematic variations are 0 on average. Thus, the tuning distance can be calculated as
326 double tuning_distance = fabrication_bias_freq - (T - T_min) * tuning_efficiency;
327
328 // Tuning power needed is just the number of rings * tuning distance / (tuning and heating efficiencies)
329 tuning_power = number_rings * tuning_distance / (tuning_efficiency * heating_efficiency);
330 }
331 else if (tuning_method == "AthermalWithTrim")
332 {
333 // Athermal! Each ring's process variations are trimmed! Everything is free!
334 // Basically an ideal scenario
335 tuning_power = 0;
336 }
337 else
338 {
339 ASSERT(false, "[Error] " + getInstanceName() + " -> Unknown ring tuning method '" + tuning_method + "'!");
340 }
341
342 return tuning_power;
343 }
344
345 unsigned int OpticalLinkBackendTx::getBitReorderDegree()
346 {
347 // Get properties
348 unsigned int number_rings = getGenProperties()->get("OutBits");
349
350 // Get tech model parameters
351 double R = getTechModel()->get("Ring->Radius");
352 double n_g = getTechModel()->get("Ring->GroupIndex");
353 // This can actually be derived if we know thermo-optic coefficient (delta n / delta T)
354 double sigma_r_local = getTechModel()->get("Ring->LocalVariationSigma");
355
356 // Get constants
357 double c = Constants::c;
358 double pi = Constants::pi;
359
360 // Calculates the degree of bit re-order multiplexing needed for bit-reshuffling backend
361 // Bit reshuffling tuning is largely unaffected by sigma_r_systematic. However, sigma_r_local
362 // Can potentially throw each ring to a channel several channels away. This just calculates
363 // the degree of bit reorder muxing needed to realign bits in the correct order
364
365 // Setup calculations
366 double L = 2 * pi * R; // Optical length
367 double FSR = c / (n_g * L); // Free spectral range
368 double freq_sep = FSR / number_rings; // Channel separation
369 // Using 4 sigmas as the worst re-ordering case (must double to get both sides)
370 unsigned int worst_case_channels = (unsigned int)ceil(2.0 * 4.0 * sigma_r_local / freq_sep);
371
372 return worst_case_channels;
373 }
374
375} // namespace DSENT
376
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