add variable explanation in doxygen format

source/module_base/global_variable.cpp

@@ -107,26 +107,19 @@ std::vector<double> ocp_kb;
 bool out_mul = false; // qifeng add 2019/9/10
 //----------------------------------------------------------
 // EXPLAIN : Parallel information
-// GLOBAL VARIABLES :
-// NAME : NPROC( global number of process )
-// NAME : KPAR( global number of pools )
-// NAME : MY_RANK( global index of process )
-// NAME : MY_POOL( global index of pool (count in pool))
-// NAME : NPROC_IN_POOL( local number of process in a pool.)
-// NAME : RANK_IN_POOL( global index of pool (count in process),
-//  		my_rank in each pool)
 //----------------------------------------------------------
-int NPROC = 1;
-int KPAR = 1;
+
+int NPROC = 1; ///< global number of process
+int KPAR = 1; ///< global number of pools
 int NSTOGROUP = 1;
-int MY_RANK = 0;
-int MY_POOL = 0;
+int MY_RANK = 0; ///< global index of process
+int MY_POOL = 0; ///< global index of pool (count in pool)
 int MY_STOGROUP = 0;
-int NPROC_IN_POOL = 1;
+int NPROC_IN_POOL = 1; ///< local number of process in a pool
 int NPROC_IN_STOGROUP = 1;
-int RANK_IN_POOL = 0;
+int RANK_IN_POOL = 0; ///< global index of pool (count in process), my_rank in each pool
 int RANK_IN_STOGROUP = 0;
-int DRANK = -1; // mohan add 2012-01-13, must be -1, so we can recognize who didn't in DIAG_WORLD
+int DRANK = -1; ///< mohan add 2012-01-13, must be -1, so we can recognize who didn't in DIAG_WORLD
 int DSIZE = KPAR;
 int DCOLOR = -1;
 int GRANK = MY_RANK;
@@ -236,7 +229,7 @@ double of_tole = 2e-6;
 double of_tolp = 1e-5;
 double of_tf_weight = 1.;
 double of_vw_weight = 1.;
-double of_wt_alpha = 5./6.;  
+double of_wt_alpha = 5./6.;
 double of_wt_beta = 5./6.;
 double of_wt_rho0 = 0.;
 bool of_hold_rho0 = false;