LAPI_Rmw 子例程

#include <lapi.h>
 
int LAPI_Rmw(hndl, op, tgt, tgt_var, in_val, prev_tgt_val, org_cntr)
 
lapi_handle_t hndl;
RMW_ops_t op;
uint tgt;
int *tgt_var;
int *in_val;
int *prev_tgt_val;
lapi_cntr_t *org_cntr;

include 'lapif.h'
 
LAPI_RMW(hndl, op, tgt, tgt_var, in_val, prev_tgt_val, org_cntr, ierror)
INTEGER hndl
INTEGER op
INTEGER tgt
INTEGER (KIND=LAPI_ADDR_TYPE) :: tgt_var
INTEGER in_val
INTEGER prev_tgt_val
TYPE (LAPI_CNTR_T) :: org_cntr
INTEGER ierror

这些操作 (op) 是在 hndl所引用的上下文上执行的。 执行这些调用的结果就像以原子方式执行了以下代码一样:

*prev_tgt_val = *tgt_var;
*tgt_var      = f(*tgt_var, *in_val);

对于 COMPARE_AND_SWAP， in_val 被视为指向两个整数的数组的指针。 op 是以下原子操作:

 if(*tgt_var == in_val[0]) {
   *prev_tgt_val = TRUE;
   *tgt_var      = in_val[1];
} else {
   *prev_tgt_val = FALSE;
}

1. 要在两个任务 (使用 FETCH_AND_ADD) 之间同步数据值，请执行以下操作:

   {
   
          int local_var;
          int *addr_list;
   
          /* both tasks initialize local_var to a value       */
   
          /* local_var addresses are exchanged and stored     */
          /* in addr_list (using LAPI_Address_init).          */
          /* addr_list[tgt] now contains the address of       */
          /* local_var on tgt                                 */
          .
          .
          .
          /* add value to local_var on some task               */
   
          /* use LAPI to add value to local_var on remote task */
          LAPI_Rmw(hndl, FETCH_AND_ADD, tgt, addr_list[tgt],
                   value, prev_tgt_val, &org_cntr);
   
          /* local_var on the remote task has been increased   */
          /* by value.  prev_tgt_val now contains the value    */
          /* of local_var on remote task before the addition   */
   
   }
   

2. 要在两个任务 (使用 SWAP) 之间同步数据值，请执行以下操作:

   
   {
   
         int local_var;
         int *addr_list;
   
         /* local_var addresses are exchanged and stored  */
         /* in addr_list (using LAPI_Address_init).       */
         /* addr_list[tgt] now contains the address of    */
         /* local_var on tgt.                             */
         .
         .
         . 
         /* local_var is assigned some value              */
   
         /* assign local_var to local_var on remote task  */
         LAPI_Rmw(hndl, SWAP, tgt, addr_list[tgt],
                  local_var, prev_tgt_val, &org_cntr);
   
         /* local_var on the remote task is now equal to  */ 
         /* local_var on the local task. prev_tgt_val now */ 
         /* contains the value of local_var on the remote */  
         /* task before the swap.                         */
   
   }
   

3. 要有条件地交换数据值 (与 COMPARE_AND_SWAP):

   
   {
   
         int local_var;
         int *addr_list;
         int in_val[2];
   
         /* local_var addresses are exchanged and stored        */
         /* in addr_list (using LAPI_Address_init).             */
         /* addr_list[tgt] now contains the address of          */
         /* local_var on tgt.                                   */
         .
         .
         .
         /* if local_var on remote_task is equal to comparator, */
         /* assign value to local_var on remote task            */
   			
         in_val[0] = comparator;
         in_val[1] = value;
   
         LAPI_Rmw(hndl, COMPARE_AND_SWAP, tgt, addr_list[tgt],
                  in_val, prev_tgt_val, &org_cntr);
   
         /* local_var on the remote task is now in_val[1] if it */
         /* had previously been equal to in_val[0]. If the swap */
         /* was performed, prev_tgt_val now contains TRUE;      */ 
         /* otherwise, it contains FALSE.                       */
   
   }