USe size_type not int

src/utils/math_funcs.hpp

@@ -746,8 +746,8 @@ void rank(const double* a, double* rank, int* index, const size_type size)
 {
     std::iota(index, index + size, 0);
     std::sort(index, index + size, [a](int i1, int i2) { return a[i1] < a[i2]; });
-    int ii = 1;
-    int ii_start = 0;
+    size_type ii = 1;
+    size_type ii_start = 0;
     while (ii_start < size)
     {
         while ((ii < size) && (std::abs(a[index[ii]] - a[index[ii - 1]]) <
@@ -756,7 +756,7 @@ void rank(const double* a, double* rank, int* index, const size_type size)
             ++ii;
         }
 
-        for (int jj = ii_start; jj < ii; ++jj)
+        for (size_type jj = ii_start; jj < ii; ++jj)
         {
             rank[index[jj]] = static_cast<double>(ii + ii_start - 1) / 2.0 + 1.0;
         }