EcalEBTrigPrimAlgos/interface/EcalEBPhase2TimeReconstructor.h

0001 #ifndef SimCalorimetry_EcalEBTrigPrimAlgos_EcalEBPhase2TimeReconstructor_h
0002 #define SimCalorimetry_EcalEBTrigPrimAlgos_EcalEBPhase2TimeReconstructor_h
0003
0004 #include <vector>
0005 #include <cstdint>
0006
0007 class EcalEBPhase2TPGTimeWeightIdMap;
0008 class EcalTPGWeightGroup;
0009
0010 /** \class EcalEBPhase2TimeReconstructor
0011 \author L. Lutton, N. Marinelli - Univ. of Notre Dame
0012  Description: forPhase II
0013  Measures the timing of a xTal signal
0014 */
0015
0016 class EcalEBPhase2TimeReconstructor {
0017 private:
0018   static const int maxSamplesUsed_ = 12;
0019   bool debug_;
0020   int inputsAlreadyIn_;
0021   int buffer_[maxSamplesUsed_];
0022   int weights_[maxSamplesUsed_];
0023   uint64_t ampIn_[maxSamplesUsed_];
0024   int shift_;
0025   bool extraShift_[2] = {false, false};
0026   int setInput(int input);
0027   void process();
0028   int processedOutput_;
0029
0030   // The array invAmpPar is pre-calulated, at least for now since it has shown to be stable. We might decide at a later stage
0031   // to make the calculation dynamic in CMSSW.
0032   // Here some explnation of what this LUT is.
0033
0034   //The sum of the digis multiplied by the time weight coefficients gives dT*A, where A is the amplitude.
0035   //So to get dT the amplitude, calculated in EcalEBPhase2AmplitudeReconstructor, must be divided off of the result here.
0036   //However, when this is implemented into the BCP hardware (of which we are emulating the behaviour),
0037   //division is not a trivial operation, often requiring relatively large
0038   //amounts of time and resources to complete.
0039   //To optimize this operation, we instead use an approximation of that division via a lookup table (LUT).
0040   //Think about the division as a multiplication of 1/A, then the LUT is filled with all the possible values of 1/A,
0041   //precalculated, in the range that A takes and A itself is used to index the LUT.
0042   //The element received is then multiplied by the dT*A result in order to get a measurement of the timing.
0043
0044   //Another limitation of hardware is that we do not use floating point numbers.
0045   //So, instead, each element of the LUT is bit shifted to the left by some amount sufficient to make every element
0046   //of the LUT large enough such that converting it to an integer doesn't lead to a loss in performance
0047   //(this bit shift is undone after the multiplication by a corresponding bit shift to the right).
0048   //Another method of approximation used here is that not every element in A's range is included in the LUT.
0049   //Instead, every 8th element is used, since the difference between, e.g., dividing by 1000 and 1008 is generally
0050   //small whereas it can be a significant save in time and resources in hardware to use a smaller LUT.
0051   //Note that this requires the indexing amplitude to be bit shifted by 3 to the right to compensate for the smaller size of the LUT.
0052   //Finally, dT will be in units of ns, but to convert it to ps each element of the LUT is multiplied by 1000.
0053
0054   //The pre-calculation of the LUT is given by:
0055   //invAmpAr_ = [1000*invMult] #Since 1/0 is undefined, the array starts with 1/1. The rest of the elements will be filled in the following loop:
0056   //for i in range(8,4096,8): #loop is set to do every 8th number, so 1/8, 1/16, 1/24, etc. 4096 is the expected range of A
0057   //invAmpAr_.append(round((ns_to_ps_conv/i)*invMult))
0058   //Where ns_to_ps_conv = 1000 #this is to convert the resulting dT from units of ns to units of ps
0059   //invMult = 2**18 #Acts as a shift by 18 bits that is done to the fractions to make them integers instead of floats.
0060
0061   uint64_t invAmpAr_[512] = {
0062       262144000, 32768000, 16384000, 10922667, 8192000, 6553600, 5461333, 4681143, 4096000, 3640889, 3276800, 2978909,
0063       2730667,   2520615,  2340571,  2184533,  2048000, 1927529, 1820444, 1724632, 1638400, 1560381, 1489455, 1424696,
0064       1365333,   1310720,  1260308,  1213630,  1170286, 1129931, 1092267, 1057032, 1024000, 992970,  963765,  936229,
0065       910222,    885622,   862316,   840205,   819200,  799220,  780190,  762047,  744727,  728178,  712348,  697191,
0066       682667,    668735,   655360,   642510,   630154,  618264,  606815,  595782,  585143,  574877,  564966,  555390,
0067       546133,    537180,   528516,   520127,   512000,  504123,  496485,  489075,  481882,  474899,  468114,  461521,
0068       455111,    448877,   442811,   436907,   431158,  425558,  420103,  414785,  409600,  404543,  399610,  394795,
0069       390095,    385506,   381023,   376644,   372364,  368180,  364089,  360088,  356174,  352344,  348596,  344926,
0070       341333,    337814,   334367,   330990,   327680,  324436,  321255,  318136,  315077,  312076,  309132,  306243,
0071       303407,    300624,   297891,   295207,   292571,  289982,  287439,  284939,  282483,  280068,  277695,  275361,
0072       273067,    270810,   268590,   266407,   264258,  262144,  260063,  258016,  256000,  254016,  252062,  250137,
0073       248242,    246376,   244537,   242726,   240941,  239182,  237449,  235741,  234057,  232397,  230761,  229147,
0074       227556,    225986,   224438,   222912,   221405,  219919,  218453,  217007,  215579,  214170,  212779,  211406,
0075       210051,    208713,   207392,   206088,   204800,  203528,  202272,  201031,  199805,  198594,  197398,  196216,
0076       195048,    193893,   192753,   191626,   190512,  189410,  188322,  187246,  186182,  185130,  184090,  183061,
0077       182044,    181039,   180044,   179060,   178087,  177124,  176172,  175230,  174298,  173376,  172463,  171560,
0078       170667,    169782,   168907,   168041,   167184,  166335,  165495,  164663,  163840,  163025,  162218,  161419,
0079       160627,    159844,   159068,   158300,   157538,  156785,  156038,  155299,  154566,  153840,  153121,  152409,
0080       151704,    151005,   150312,   149626,   148945,  148271,  147604,  146942,  146286,  145636,  144991,  144352,
0081       143719,    143092,   142470,   141853,   141241,  140635,  140034,  139438,  138847,  138262,  137681,  137105,
0082       136533,    135967,   135405,   134848,   134295,  133747,  133203,  132664,  132129,  131598,  131072,  130550,
0083       130032,    129518,   129008,   128502,   128000,  127502,  127008,  126517,  126031,  125548,  125069,  124593,
0084       124121,    123653,   123188,   122727,   122269,  121814,  121363,  120915,  120471,  120029,  119591,  119156,
0085       118725,    118296,   117871,   117448,   117029,  116612,  116199,  115788,  115380,  114975,  114573,  114174,
0086       113778,    113384,   112993,   112605,   112219,  111836,  111456,  111078,  110703,  110330,  109960,  109592,
0087       109227,    108864,   108503,   108145,   107789,  107436,  107085,  106736,  106390,  106045,  105703,  105363,
0088       105026,    104690,   104357,   104025,   103696,  103369,  103044,  102721,  102400,  102081,  101764,  101449,
0089       101136,    100825,   100515,   100208,   99902,   99599,   99297,   98997,   98699,   98402,   98108,   97815,
0090       97524,     97234,    96947,    96661,    96376,   96094,   95813,   95534,   95256,   94980,   94705,   94432,
0091       94161,     93891,    93623,    93356,    93091,   92827,   92565,   92304,   92045,   91787,   91531,   91276,
0092       91022,     90770,    90519,    90270,    90022,   89775,   89530,   89286,   89043,   88802,   88562,   88323,
0093       88086,     87850,    87615,    87381,    87149,   86918,   86688,   86459,   86232,   86005,   85780,   85556,
0094       85333,     85112,    84891,    84672,    84454,   84237,   84021,   83806,   83592,   83379,   83168,   82957,
0095       82747,     82539,    82332,    82125,    81920,   81716,   81512,   81310,   81109,   80909,   80709,   80511,
0096       80314,     80117,    79922,    79727,    79534,   79341,   79150,   78959,   78769,   78580,   78392,   78205,
0097       78019,     77834,    77649,    77466,    77283,   77101,   76920,   76740,   76561,   76382,   76205,   76028,
0098       75852,     75677,    75502,    75329,    75156,   74984,   74813,   74642,   74473,   74304,   74136,   73968,
0099       73802,     73636,    73471,    73306,    73143,   72980,   72818,   72656,   72496,   72336,   72176,   72018,
0100       71860,     71702,    71546,    71390,    71235,   71080,   70926,   70773,   70621,   70469,   70318,   70167,
0101       70017,     69868,    69719,    69571,    69424,   69277,   69131,   68985,   68840,   68696,   68552,   68409,
0102       68267,     68125,    67983,    67843,    67702,   67563,   67424,   67285,   67148,   67010,   66873,   66737,
0103       66602,     66467,    66332,    66198,    66065,   65932,   65799,   65667,   65536,   65405,   65275,   65145,
0104       65016,     64887,    64759,    64631,    64504,   64377,   64251,   64125};
0105
0106 public:
0107   EcalEBPhase2TimeReconstructor(bool debug);
0108   virtual ~EcalEBPhase2TimeReconstructor();
0109   virtual void process(std::vector<int> &addout, std::vector<int> &ampRecoOutput, std::vector<int64_t> &output);
0110   void setParameters(uint32_t raw,
0111                      const EcalEBPhase2TPGTimeWeightIdMap *ecaltpgTimeWeightMap,
0112                      const EcalTPGWeightGroup *ecaltpgWeightGroup);
0113 };
0114
0115 #endif