Initialize variables at declaration if it improves readability (#4117)

* init some variables at declaration

* make code more readable

* avoid lossy function result cast

* Update Source/Initialization/WarpXInitData.cpp

Co-authored-by: Weiqun Zhang <WeiqunZhang@lbl.gov>

* replace with equality

* Revert "replace with equality"

This reverts commit e3164f9e053d345b153d770ae107a7f68c4bb260.

* Update Source/Diagnostics/ComputeDiagFunctors/ParticleReductionFunctor.cpp

Co-authored-by: Weiqun Zhang <WeiqunZhang@lbl.gov>

---------

Co-authored-by: Weiqun Zhang <WeiqunZhang@lbl.gov>

2 files changed, 3 insertions, 12 deletions

diff --git a/Source/Particles/Collision/BinaryCollision/NuclearFusion/NuclearFusionFunc.H b/Source/Particles/Collision/BinaryCollision/NuclearFusion/NuclearFusionFunc.H
index 9bcec2606..23939bbc2 100644
--- a/Source/Particles/Collision/BinaryCollision/NuclearFusion/NuclearFusionFunc.H
+++ b/Source/Particles/Collision/BinaryCollision/NuclearFusion/NuclearFusionFunc.H
@@ -161,15 +161,7 @@ public:
             const int c2 = amrex::max(NI1/NI2,1);
 
             // multiplier ratio to take into account unsampled pairs
-            int multiplier_ratio;
-            if (m_isSameSpecies)
-            {
-                multiplier_ratio = 2*max_N - 1;
-            }
-            else
-            {
-                multiplier_ratio = max_N;
-            }
+            const int multiplier_ratio = (m_isSameSpecies)?(2*max_N - 1):(max_N);
 
 #if (defined WARPX_DIM_RZ)
             amrex::ParticleReal * const AMREX_RESTRICT theta1 = soa_1.m_rdata[PIdx::theta];
diff --git a/Source/Particles/Collision/BinaryCollision/ShuffleFisherYates.H b/Source/Particles/Collision/BinaryCollision/ShuffleFisherYates.H
index d7a302e3a..42259512b 100644
--- a/Source/Particles/Collision/BinaryCollision/ShuffleFisherYates.H
+++ b/Source/Particles/Collision/BinaryCollision/ShuffleFisherYates.H
@@ -20,13 +20,12 @@ AMREX_GPU_HOST_DEVICE AMREX_INLINE
 void ShuffleFisherYates (T_index *array, T_index const is, T_index const ie,
                          amrex::RandomEngine const& engine)
 {
-    int     j;
     T_index buf;
     for (int i = ie-1; i >= static_cast<int>(is+1); --i)
     {
         // get random number j: is <= j <= i
-        j = amrex::Random_int(i-is+1, engine) + is;
-        // swop the ith array element with the jth
+        const int j = amrex::Random_int(i-is+1, engine) + is;
+        // swap the ith array element with the jth
         buf      = array[i];
         array[i] = array[j];
         array[j] = buf;