Enable Build with FFTW in One Precision

FFTW can be built in multiple precisions, but we will
only use one at a time with `amrex::Real`. Pick the one
we really use, do not require more than that.

This will simplify specifications and requirements in package
management.

Src/FFT/AMReX_FFT.cpp

@@ -9,8 +9,11 @@ namespace amrex::FFT
 namespace
 {
     bool s_initialized = false;
-    std::map<Key, PlanD> s_plans_d;
+#ifdef AMREX_USE_FLOAT
     std::map<Key, PlanF> s_plans_f;
+#else
+    std::map<Key, PlanD> s_plans_d;
+#endif
 }
 
 void Initialize ()
@@ -43,42 +46,48 @@ void Finalize ()
 
 void Clear ()
 {
-    for (auto& [k, p] : s_plans_d) {
-        Plan<double>::destroy_vendor_plan(p);
-    }
-
+#ifdef AMREX_USE_FLOAT
     for (auto& [k, p] : s_plans_f) {
         Plan<float>::destroy_vendor_plan(p);
     }
+#else
+    for (auto& [k, p] : s_plans_d) {
+        Plan<double>::destroy_vendor_plan(p);
+    }
+#endif
 }
 
-PlanD* get_vendor_plan_d (Key const& key)
+#ifdef AMREX_USE_FLOAT
+PlanF* get_vendor_plan_f (Key const& key)
 {
-    if (auto found = s_plans_d.find(key); found != s_plans_d.end()) {
+    if (auto found = s_plans_f.find(key); found != s_plans_f.end()) {
         return &(found->second);
     } else {
         return nullptr;
     }
 }
-
-PlanF* get_vendor_plan_f (Key const& key)
+#else
+PlanD* get_vendor_plan_d (Key const& key)
 {
-    if (auto found = s_plans_f.find(key); found != s_plans_f.end()) {
+    if (auto found = s_plans_d.find(key); found != s_plans_d.end()) {
         return &(found->second);
     } else {
         return nullptr;
     }
 }
+#endif
 
-void add_vendor_plan_d (Key const& key, PlanD plan)
-{
-    s_plans_d[key] = plan;
-}
-
+#ifdef AMREX_USE_FLOAT
 void add_vendor_plan_f (Key const& key, PlanF plan)
 {
     s_plans_f[key] = plan;
 }
+#else
+void add_vendor_plan_d (Key const& key, PlanD plan)
+{
+    s_plans_d[key] = plan;
+}
+#endif
 
 }
 

Src/FFT/AMReX_FFT_Helper.H

@@ -1132,14 +1132,16 @@ struct Plan
 };
 
 using Key = std::tuple<IntVectND<3>,Direction,Kind>;
-using PlanD = typename Plan<double>::VendorPlan;
-using PlanF = typename Plan<float>::VendorPlan;
 
-PlanD* get_vendor_plan_d (Key const& key);
+#ifdef AMREX_USE_FLOAT
+using PlanF = typename Plan<float>::VendorPlan;
 PlanF* get_vendor_plan_f (Key const& key);
-
-void add_vendor_plan_d (Key const& key, PlanD plan);
 void add_vendor_plan_f (Key const& key, PlanF plan);
+#else
+using PlanD = typename Plan<double>::VendorPlan;
+PlanD* get_vendor_plan_d (Key const& key);
+void add_vendor_plan_d (Key const& key, PlanD plan);
+#endif
 
 template <typename T>
 template <Direction D, int M>