Fix warnings

Author: WeiqunZhang

Src/Extern/openPMD-api/AMReX_ParticlesOPENPMD.H

@@ -18,7 +18,7 @@ struct AMReX_PtlCounter
 
   std::vector<unsigned long long> m_ParticleCounterByLevel;
 
-  unsigned long GetTotalNumParticles () const { return m_Total;}
+  [[nodiscard]] unsigned long long GetTotalNumParticles () const { return m_Total;}
 
   std::vector<unsigned long long> m_ParticleOffsetAtRank;
   std::vector<unsigned long long> m_ParticleSizeAtRank;
@@ -35,31 +35,27 @@ void CountParticles()
   m_PtlCounter.m_ParticleOffsetAtRank.resize(this->finestLevel()+1);
   m_PtlCounter.m_ParticleSizeAtRank.resize(this->finestLevel()+1);
 
-  auto lf_GetParticleOffsetOfProcessor = [&](const long& numParticles,
+  auto lf_GetParticleOffsetOfProcessor = [&](const long long& numParticles,
                                              unsigned long long& offset,
                                              unsigned long long& sum)  -> void
   {
-    std::vector<long> result(m_PtlCounter.m_MPISize,  0);
+    std::vector<long long> result(m_PtlCounter.m_MPISize,  0);
     amrex::ParallelGather::Gather (numParticles, result.data(), -1, amrex::ParallelDescriptor::Communicator());
 
     sum = 0;
     offset = 0;
-    for (int i=0;  i<result.size();  i++) {
+    for (int i=0;  i<int(result.size());  i++) {
       sum +=  result[i];
-      if ( i < m_PtlCounter.m_MPIRank)
+      if ( i < m_PtlCounter.m_MPIRank) {
         offset +=  result[i];
+      }
     }
   };
 
   for (auto currentLevel = 0; currentLevel <= this->finestLevel(); currentLevel++)
     {
-      long numParticles = 0; // numParticles in this processor
-
-      //for (ParIter pti(*this, currentLevel); pti.isValid(); ++pti) {
-      for (ParConstIterType pti(*this, currentLevel); pti.isValid(); ++pti) {
-        auto numParticleOnTile = pti.numParticles();
-        numParticles += numParticleOnTile;
-      }
+      // numParticles in this processor
+      auto numParticles = static_cast<long long>(this->NumberOfParticlesAtLevel(currentLevel, false, false));
 
       unsigned long long offset=0; // offset of this level
       unsigned long long sum=0; // numParticles in this level (sum from all processors)
@@ -81,5 +77,3 @@ void CountParticles()
 
 AMReX_PtlCounter m_PtlCounter;
 #endif // AMREX_PTL_OPENPMD_API_H
-
-