avoid repeated function evaluations and force compile-time evaluation

improves code performance by an order of magnitude when compiled with Clang-based compilers.
rabauke · May 9, 2024 · d5afd97 · d5afd97
1 parent ab92829
commit d5afd97
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Showing 4 changed files with 14 additions and 14 deletions.
diff --git a/trng/lagfib2plus.hpp b/trng/lagfib2plus.hpp
@@ -235,10 +235,10 @@ namespace trng {
     status_type S;
 
     void step() {
+      constexpr auto mask_B{int_math::mask(static_cast<decltype(S.index)>(B))};
       ++S.index;
-      S.index &= int_math::mask(B);
-      S.r[S.index] =
-          S.r[(S.index - A) & int_math::mask(B)] + S.r[(S.index - B) & int_math::mask(B)];
+      S.index &= mask_B;
+      S.r[S.index] = S.r[(S.index - A) & mask_B] + S.r[(S.index - B) & mask_B];
     }
   };
 

diff --git a/trng/lagfib2xor.hpp b/trng/lagfib2xor.hpp
@@ -237,10 +237,10 @@ namespace trng {
     status_type S;
 
     void step() {
+      constexpr auto mask_B{int_math::mask(static_cast<decltype(S.index)>(B))};
       ++S.index;
-      S.index &= int_math::mask(B);
-      S.r[S.index] =
-          S.r[(S.index - A) & int_math::mask(B)] ^ S.r[(S.index - B) & int_math::mask(B)];
+      S.index &= mask_B;
+      S.r[S.index] = S.r[(S.index - A) & mask_B] ^ S.r[(S.index - B) & mask_B];
     }
   };
 

diff --git a/trng/lagfib4plus.hpp b/trng/lagfib4plus.hpp
@@ -237,11 +237,11 @@ namespace trng {
     status_type S;
 
     void step() {
+      constexpr auto mask_D{int_math::mask(static_cast<decltype(S.index)>(D))};
       ++S.index;
-      S.index &= int_math::mask(D);
-      S.r[S.index] =
-          S.r[(S.index - A) & int_math::mask(D)] + S.r[(S.index - B) & int_math::mask(D)] +
-          S.r[(S.index - C) & int_math::mask(D)] + S.r[(S.index - D) & int_math::mask(D)];
+      S.index &= mask_D;
+      S.r[S.index] = S.r[(S.index - A) & mask_D] + S.r[(S.index - B) & mask_D] +
+                     S.r[(S.index - C) & mask_D] + S.r[(S.index - D) & mask_D];
     }
   };
 

diff --git a/trng/lagfib4xor.hpp b/trng/lagfib4xor.hpp
@@ -240,11 +240,11 @@ namespace trng {
     status_type S;
 
     void step() {
+      constexpr auto mask_D{int_math::mask(static_cast<decltype(S.index)>(D))};
       ++S.index;
-      S.index &= int_math::mask(D);
-      S.r[S.index] =
-          S.r[(S.index - A) & int_math::mask(D)] ^ S.r[(S.index - B) & int_math::mask(D)] ^
-          S.r[(S.index - C) & int_math::mask(D)] ^ S.r[(S.index - D) & int_math::mask(D)];
+      S.index &= mask_D;
+      S.r[S.index] = S.r[(S.index - A) & mask_D] ^ S.r[(S.index - B) & mask_D] ^
+                     S.r[(S.index - C) & mask_D] ^ S.r[(S.index - D) & mask_D];
     }
   };