abap 用代码实现两层loop循环优化

在 ABAP 中，可以使用以下方法优化两层循环：

1. 将内层循环中的计算结果存储到一个临时表中，然后在外层循环中使用这些计算结果。这样可以减少内层循环的执行次数。

DATA: lt_temp TYPE TABLE OF ty_temp,
      ls_temp TYPE ty_temp.

LOOP AT itab INTO wa_itab.
  LOOP AT itab2 INTO wa_itab2.
    ls_temp-field1 = wa_itab-field1 + wa_itab2-field2.
    ls_temp-field2 = wa_itab-field2 + wa_itab2-field1.
    APPEND ls_temp TO lt_temp.
  ENDLOOP.
ENDLOOP.

LOOP AT lt_temp INTO ls_temp.
  " Use the calculated values
ENDLOOP.

2. 将内层循环中的计算结果存储到一个哈希表中，然后在外层循环中使用这些计算结果。这样可以减少内层循环的执行次数，并且哈希表查找速度比临时表更快。

TYPES: BEGIN OF ty_temp,
         field1 TYPE i,
         field2 TYPE i,
       END OF ty_temp.

DATA: lt_temp TYPE HASHED TABLE OF ty_temp WITH UNIQUE KEY field1 field2,
      ls_temp TYPE ty_temp.

LOOP AT itab INTO wa_itab.
  LOOP AT itab2 INTO wa_itab2.
    ls_temp-field1 = wa_itab-field1 + wa_itab2-field2.
    ls_temp-field2 = wa_itab-field2 + wa_itab2-field1.
    lt_temp = VALUE #( BASE lt_temp ( ls_temp ) ).
  ENDLOOP.
ENDLOOP.

LOOP AT itab INTO wa_itab.
  READ TABLE lt_temp INTO ls_temp WITH KEY field1 = wa_itab-field1 field2 = wa_itab-field2.
  IF sy-subrc = 0.
    " Use the calculated values
  ENDIF.
ENDLOOP.