Added function to compute a value to the power of inverse dimenstion effectively.

src/dimension.h

@@ -89,6 +89,34 @@ __attribute__((always_inline)) INLINE static float pow_dimension(float x) {
 #endif
 }
 
+/**
+ * @brief Returns the argument to the power given by the inverse of the
+ * dimension
+ *
+ * Computes \f$x^{1/d}\f$.
+ */
+__attribute__((always_inline)) INLINE static float pow_inv_dimension(float x) {
+
+#if defined(HYDRO_DIMENSION_3D)
+
+  return cbrtf(x);
+
+#elif defined(HYDRO_DIMENSION_2D)
+
+  return sqrtf(x);
+
+#elif defined(HYDRO_DIMENSION_1D)
+
+  return x;
+
+#else
+
+  error("The dimension is not defined !");
+  return 0.f;
+
+#endif
+}
+
 /**
  * @brief Returns the argument to the power given by the dimension plus one
  *