Do not resize to 0 in windows

Author: filikat

highs/ipm/hipo/auxiliary/Auxiliary.cpp

@@ -208,6 +208,15 @@ Int64 getDiagStart(Int n, Int k, Int nb, Int n_blocks,
   return result;
 }
 
+Int64 sizeAtLeastOne(Int64 size) {
+  // When resizing vectors on windows, if the size is 0, there can be problems
+  // later on accessing the entry at address 0. So always allocate at least one
+  // byte.
+
+  if (0 == size) ++size;
+  return size;
+}
+
 Clock::Clock() { start(); }
 void Clock::start() { t0 = std::chrono::high_resolution_clock::now(); }
 double Clock::stop() const {

highs/ipm/hipo/auxiliary/Auxiliary.h

@@ -28,6 +28,7 @@ void processEdge(Int j, Int i, const std::vector<Int>& first,
                  std::vector<Int>& prevleaf, std::vector<Int>& ancestor);
 Int64 getDiagStart(Int n, Int k, Int nb, Int n_blocks,
                    std::vector<Int64>& start, bool triang = false);
+Int64 sizeAtLeastOne(Int64 size);
 
 template <typename T>
 void counts2Ptr(std::vector<T>& ptr, std::vector<T>& w) {

highs/ipm/hipo/factorhighs/CliqueStack.cpp

@@ -3,9 +3,13 @@
 #include <cassert>
 #include <cstring>
 
+#include "ipm/hipo/auxiliary/Auxiliary.h"
+
 namespace hipo {
 
 void CliqueStack::init(Int64 stack_size) {
+  stack_size = sizeAtLeastOne(stack_size);
+
   stack_.resize(stack_size, 0.0);
   top_ = 0;
   workspace_ = nullptr;

highs/ipm/hipo/factorhighs/FormatHandler.h

@@ -88,8 +88,6 @@ class FormatHandler {
   virtual void extremeEntries() {}
 };
 
-const Int64 extra_space = 10;
-
 }  // namespace hipo
 
 #endif

highs/ipm/hipo/factorhighs/HybridHybridFormatHandler.cpp

@@ -24,20 +24,19 @@ HybridHybridFormatHandler::HybridHybridFormatHandler(
 void HybridHybridFormatHandler::initFrontal() {
   const Int n_blocks = (sn_size_ - 1) / nb_ + 1;
   diag_start_.resize(n_blocks);
-  Int64 frontal_size =
-      getDiagStart(ldf_, sn_size_, nb_, n_blocks, diag_start_) + extra_space;
+  Int64 frontal_size = getDiagStart(ldf_, sn_size_, nb_, n_blocks, diag_start_);
+  frontal_size = sizeAtLeastOne(frontal_size);
   frontal_.resize(frontal_size);
   std::memset(frontal_.data(), 0, frontal_size * sizeof(double));
 
-  // extra_space is not needed, but if I remove it Windows in debug freezes...
-  // who knows what's happening
-
   // frontal_ is actually allocated just the first time, then the memory is
   // reused from the previous factorisations and just initialised.
 }
 
 void HybridHybridFormatHandler::initClique() {
-  clique_.resize(S_->cliqueSize(sn_));
+  Int64 clique_size = S_->cliqueSize(sn_);
+  clique_size = sizeAtLeastOne(clique_size);
+  clique_.resize(clique_size);
   clique_ptr_ = clique_.data();
 }
 

highs/ipm/hipo/factorhighs/HybridSolveHandler.cpp

@@ -145,7 +145,7 @@ void HybridSolveHandler::backwardSolve(std::vector<double>& x) const {
 
     // index to access snColumns[sn]
     // initialised with the total number of entries of snColumns[sn]
-    Int64 SnCol_ind = sn_columns_[sn].size() - extra_space;
+    Int64 SnCol_ind = sn_columns_[sn].size();
 
     // go through blocks of columns for this supernode in reverse order
     for (Int j = n_blocks - 1; j >= 0; --j) {