+/** \ingroup TRACE_user_variables
+ * \brief Declare a new user variable associated to hosts.
+ *
+ * Declare a user variable that will be associated to hosts.
+ * A user host variable can be used to trace user variables
+ * such as the number of tasks in a server, the number of
+ * clients in an application (for hosts), and so on. The color
+ * associated to this new variable will be random.
+ *
+ * \param variable The name of the new variable to be declared.
+ *
+ * \see TRACE_host_variable_declare_with_color
+ */
+void TRACE_host_variable_declare (const char *variable)
+{
+ instr_user_variable(0, NULL, variable, "HOST", 0, INSTR_US_DECLARE, NULL, user_host_variables);
+}
+
+/** \ingroup TRACE_user_variables
+ * \brief Declare a new user variable associated to hosts with a color.
+ *
+ * Same as #TRACE_host_variable_declare, but associated a color
+ * to the newly created user host variable. The color needs to be
+ * a string with three numbers separated by spaces in the range [0,1].
+ * A light-gray color can be specified using "0.7 0.7 0.7" as color.
+ *
+ * \param variable The name of the new variable to be declared.
+ * \param color The color for the new variable.
+ *
+ */
+void TRACE_host_variable_declare_with_color (const char *variable, const char *color)