diff --git a/CMakeLists.txt b/CMakeLists.txt
index f36d95b..f32a570 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -40,7 +40,7 @@ list(APPEND extra_libs fmt::fmt)
 FetchContent_Declare(
   platanus
   GIT_REPOSITORY https://github.com/sukeya/platanus.git
-  GIT_TAG        23a9ba9cd6bfe38b01fd7e87e28ae42dd8b2744f # origin/main
+  GIT_TAG        0a0f3c93a637263c0479a398d54564a74c9ad694 # origin/main
 )
 FetchContent_MakeAvailable(platanus)
 list(APPEND extra_libs platanus)
diff --git a/include/mvPolynomial/index_comparer.hpp b/include/mvPolynomial/index_comparer.hpp
index e24df20..130b635 100644
--- a/include/mvPolynomial/index_comparer.hpp
+++ b/include/mvPolynomial/index_comparer.hpp
@@ -24,17 +24,17 @@ class IndexComparer final {
   static constexpr int dim = D;
 
   /**
-   * \brief If lhd[i] == rhd[i] for i = 0, ..., N - 1 and lhd[N] > rhd[N],
-   * return greater: if lhd[N] < rhd[N], return less: otherwise, return equal.
+   * \brief If lhd[i] == rhd[i] for i = 0, ..., N - 1 and lhd[N] < rhd[N],
+   * return greater: if lhd[N] > rhd[N], return less: otherwise, return equal.
    * \param[in] lhd an index
    * \param[in] rhd an index
    */
   static constexpr std::strong_ordering Compare(const Index& lhd, const Index& rhd) {
     for (std::size_t i = 0; i < lhd.size(); ++i) {
       auto comp = lhd[i] <=> rhd[i];
-      if (comp > 0) {
+      if (comp < 0) {
         return std::strong_ordering::greater;
-      } else if (comp < 0) {
+      } else if (comp > 0) {
         return std::strong_ordering::less;
       }
     }
@@ -42,16 +42,16 @@ class IndexComparer final {
   }
 
   /**
-   * \brief If lhd[i] == rhd[i] for i = 0, ..., N - 1 and lhd[N] > rhd[N],
+   * \brief If lhd[i] == rhd[i] for i = 0, ..., N - 1 and lhd[N] < rhd[N],
    * return true: otherwise, false.
    * \param[in] lhd an index
    * \param[in] rhd an index
    */
   bool operator()(const Index& lhd, const Index& rhd) const {
     for (std::size_t i = 0; i < lhd.size(); ++i) {
-      if (lhd[i] > rhd[i]) {
+      if (lhd[i] < rhd[i]) {
         return true;
-      } else if (lhd[i] < rhd[i]) {
+      } else if (lhd[i] > rhd[i]) {
         return false;
       }
     }
diff --git a/include/mvPolynomial/mvPolynomial.hpp b/include/mvPolynomial/mvPolynomial.hpp
index 5803a87..3d19832 100644
--- a/include/mvPolynomial/mvPolynomial.hpp
+++ b/include/mvPolynomial/mvPolynomial.hpp
@@ -50,7 +50,6 @@ auto OfImpl(Iterator begin, Iterator end, int dim, int axis, const Coord& x) {
             return pair.first[axis] == first_index[axis];
           }
       );
-      const auto& [p_index, p_coeff] = *partition_point;
       sum += OfImpl(begin, partition_point, dim, axis + 1, x);
       if (partition_point == end) {
         // The calculation ends.
@@ -259,7 +258,7 @@ class MVPolynomial final {
     return index2value_.upper_bound(i);
   }
 
-  R operator()(const coord_type& x) const { return OfImpl(cbegin(), cend(), dim, 0, x); }
+  R operator()(const coord_type& x) const { return OfImpl(crbegin(), crend(), dim, 0, x); }
 
   MVPolynomial operator+() const { return *this; }
 
@@ -352,9 +351,9 @@ class MVPolynomial final {
 
  private:
   void CheckSelfIndexes() const {
-    // The last index is the lowest index of all index,
+    // The first index is the lowest index of all index,
     // so I only have to check if each of its elements is non-negative.
-    if ((std::prev(index2value_.end())->first < 0).any()) {
+    if ((index2value_.begin()->first < 0).any()) {
       throw std::invalid_argument(fmt::format("Negative index not supported!"));
     }
   }