Add statistics about tiny sn

Author: filikat

highs/ipm/hipo/factorhighs/Analyse.cpp

@@ -1277,6 +1277,15 @@ Int Analyse::run(Symbolic& S) {
     if (i <= 100) S.sn_size_100_++;
   }
 
+  // count tiny supernodes, i.e., sn with small size and with clique that fits
+  // in a single block.
+  for (Int i = 0; i < sn_count_; ++i) {
+    if (sn_size[i] <= kTinySupernodeSize &&
+        (ptr_sn_[i + 1] - ptr_sn_[i]) <= sn_size[i] + nb_) {
+      S.sn_tiny_++;
+    }
+  }
+
   if (checkOverflow()) {
     if (logger_) logger_->printe("Integer overflow in analyse phase\n");
     return kRetIntOverflow;

highs/ipm/hipo/factorhighs/FactorHiGHSSettings.h

@@ -45,6 +45,8 @@ const double kAlphaBK = 0.01;  //(sqrt(17.0) + 1.0) / 8.0;
 const Int kBlockGrainSize = 1;
 const Int kBlockParallelThreshold = 5;
 
+const Int kTinySupernodeSize = 4;
+
 const Int kMinConsecutiveSums = 1;
 
 // regularisation

highs/ipm/hipo/factorhighs/Symbolic.cpp

@@ -91,6 +91,8 @@ void Symbolic::print(const Logger& logger, bool verbose) const {
     log_stream << textline("Sn size <= 10:") << integer(sn_size_10_, 0) << '\n';
     log_stream << textline("Sn size <= 100:") << integer(sn_size_100_, 0)
                << '\n';
+    log_stream << textline("Tiny sn:") << integer(sn_tiny_) << " ("
+               << fix((double)sn_tiny_ / sn_ * 100, 0, 1) << "%%)\n";
     log_stream << textline("Sn avg size:") << sci((double)n_ / sn_, 0, 1)
                << '\n';
   }

highs/ipm/hipo/factorhighs/Symbolic.h

@@ -33,6 +33,7 @@ class Symbolic {
   Int sn_size_1_{};
   Int sn_size_10_{};
   Int sn_size_100_{};
+  Int sn_tiny_{};
 
   // Inverse permutation
   std::vector<Int> iperm_{};