feat: improved small num test

fastmath.hpp

@@ -81,6 +81,7 @@ struct decimal {
     decimal sqrt() { return {((int32_t)sqrtf(i)) << HALF_SHIFT}; }
 
     float to_float() { return TO_FLOAT(i); }
+    bool isSmall() { return (abs(i) < (1 << (HALF_SHIFT - 1))); }
 };
 
 template <int n, class Dev> struct vec {
@@ -164,7 +165,7 @@ template <int n, class Dev> struct vec {
     }
     bool isSmall() {
         for (int i = 0; i < n; i++) {
-            if (abs(v[i].i) > (1 << (HALF_SHIFT - 1)))
+            if (!v[i].isSmall())
                 return false;
         }
         return true;