Hi how to avoid nested loops in this program to improve the performence

Question

Hi all
How to avoide the nested loops in this programing what is the replacement for the nested loops in this program coding......
LOOP AT itb_ekpo.
    READ TABLE itb_marc WITH KEY
       matnr = itb_ekpo-matnr
       werks = itb_ekpo-werks BINARY SEARCH.
    CHECK sy-subrc = 0.
FAE 26446 fin remplacement
    itb_pca-ebeln = itb_ekpo-ebeln.
    itb_pca-ebelp = itb_ekpo-ebelp.
  itb_pca-lifnr = itb_ekko-lifnr.   "-FAE26446
    itb_pca-lifnr = itb_ekpo-lifnr.                         "+FAE26446
    itb_pca-ekgrp = itb_ekpo-ekgrp.                         "+FAE26446
    itb_pca-dispo = itb_ekpo-dispo.                         "+FAE26446
    itb_pca-matnr = itb_ekpo-matnr.
    itb_pca-werks = itb_ekpo-werks.
  Recherche du libellé article
    READ TABLE itb_makt
               WITH KEY matnr = itb_ekpo-matnr
                        spras = text-fra
               BINARY SEARCH.
    IF sy-subrc = 0.
      itb_pca-maktx = itb_makt-maktx.
    ELSE.
      READ TABLE itb_makt
                WITH KEY matnr = itb_ekpo-matnr
                         spras = text-ang
                BINARY SEARCH.
      IF sy-subrc = 0.
        itb_pca-maktx = itb_makt-maktx.
      ENDIF.
    ENDIF.
    IF NOT itb_ekpo-bpumn IS INITIAL.
      itb_pca-menge = itb_ekpo-menge * itb_ekpo-bpumz /
                                       itb_ekpo-bpumn.
    ENDIF.
  Sélect° ds la table EKES des dates de livraisons et des qtés
  en transit
    CLEAR w_temoin_ar.
    CLEAR w_etens.
    LOOP AT itb_ekes
            FROM w_index_ekes.
      IF  itb_ekes-ebeln = itb_ekpo-ebeln
      AND itb_ekes-ebelp = itb_ekpo-ebelp.
        IF itb_ekes-ebtyp = text-arn.
          itb_pca-eindt = itb_ekes-eindt.
          w_temoin_ar = 'X'.
        ELSE.
        Si c'est une qté en transit alors on recupere
        la quantité et la date.
          IF itb_ekes-dabmg < itb_ekes-menge.
            itb_pca-qtran = itb_pca-qtran + itb_ekes-menge -
                            itb_ekes-dabmg.
          ENDIF.
          IF itb_ekes-etens > w_etens.
            w_etens = itb_ekes-etens.
            itb_pca-dtran = itb_ekes-eindt.
          ENDIF.
        ENDIF.
      ELSEIF itb_ekes-ebeln > itb_ekpo-ebeln
      OR ( itb_ekes-ebeln = itb_ekpo-ebeln
      AND itb_ekes-ebelp > itb_ekpo-ebelp ).
        w_index_ekes = sy-tabix.
        EXIT.
      ENDIF.
    ENDLOOP.
  S'il n'y a pas d'AR alors récupérat° de la date livraison dans EKET.
    LOOP AT itb_eket
            FROM w_index_eket.
      IF  itb_eket-ebeln = itb_ekpo-ebeln
      AND itb_eket-ebelp = itb_ekpo-ebelp.
        IF w_temoin_ar IS INITIAL.
          itb_pca-eindt = itb_eket-eindt.
        ENDIF.
        itb_pca-slfdt = itb_eket-slfdt.
      Calcul du portefeuille fournisseur à partir de la
      qté commandée et la qté reçue
        itb_pca-attdu = itb_pca-attdu + itb_eket-menge -
                        itb_eket-wemng.
      Calcul du montant du poste
        itb_pca-netpr = itb_ekpo-netpr * itb_pca-attdu.
        IF itb_ekpo-peinh NE 0.
          itb_pca-netpr = itb_pca-netpr / itb_ekpo-peinh.
        ENDIF.
      Calcul quantité réceptionnée.
        itb_pca-wemng = itb_pca-wemng + itb_eket-wemng.
      Calcul du retard en nombre de jours calendaires
      Le calcul du retard  ne doit pas prendre en compte
      le jour de livraison
        ADD 1 TO itb_eket-eindt.
        IF NOT itb_pca-attdu  IS INITIAL
        AND    itb_eket-eindt LT sy-datum.
        Calcul du retard en nombre de jours ouvrés
          CLEAR w_retard.
          CALL FUNCTION 'Z_00_BC_WORKDAYS_PER_PERIOD'
               EXPORTING
                    date_deb = itb_eket-eindt
                    date_fin = sy-datum
               IMPORTING
                    jours    = w_retard.
          itb_pca-rtard = itb_pca-rtard + w_retard .
        ENDIF.
      ELSEIF itb_eket-ebeln > itb_ekpo-ebeln
      OR (   itb_eket-ebeln = itb_ekpo-ebeln
      AND    itb_eket-ebelp > itb_ekpo-ebelp ).
        w_index_eket = sy-tabix.
        EXIT.
      ENDIF.
    ENDLOOP.
  Recherche de la derniere date de livraison.
    LOOP AT itb_mseg
            FROM w_index_mseg.
      IF  itb_mseg-ebeln = itb_ekpo-ebeln
      AND itb_mseg-ebelp = itb_ekpo-ebelp.
        READ TABLE itb_mkpf
                   WITH KEY mblnr = itb_mseg-mblnr
                            mjahr = itb_mseg-mjahr
                   BINARY SEARCH.
        IF sy-subrc = 0.
          IF itb_mkpf-bldat > itb_pca-bldat.
            itb_pca-bldat = itb_mkpf-bldat.
          ENDIF.
        ENDIF.
      ELSEIF itb_mseg-ebeln > itb_ekpo-ebeln
      OR (   itb_mseg-ebeln = itb_ekpo-ebeln
      AND    itb_mseg-ebelp > itb_ekpo-ebelp ).
        w_index_mseg = sy-tabix.
        EXIT.
      ENDIF.
    ENDLOOP.
    APPEND itb_pca.
    CLEAR itb_pca.
FAE26446 suppression parag. suivant
     ELSEIF itb_ekpo-ebeln > itb_ekko-ebeln.
       w_index_ekpo = sy-tabix.
       EXIT.
     ENDIF.
   ENDLOOP.
Fin FAE26446
  ENDLOOP.
Thanks in advance for all.....

Answer 1

Hi
these are the performance tips
Instead of using nested Select loops it is often better to use subqueries.
SELECT * FROM SPFLI
  INTO TABLE T_SPFLI
  WHERE CITYFROM = 'FRANKFURT'
    AND CITYTO = 'NEW YORK'.
SELECT * FROM SFLIGHT AS F
    INTO SFLIGHT_WA
    FOR ALL ENTRIES IN T_SPFLI
    WHERE SEATSOCC < F~SEATSMAX
      AND CARRID = T_SPFLI-CARRID
      AND CONNID = T_SPFLI-CONNID
      AND FLDATE BETWEEN '19990101' AND '19990331'.
ENDSELECT.
The above mentioned code can be even more optimized by using subqueries instead of for all entries.
SELECT * FROM SFLIGHT AS F INTO SFLIGHT_WA
    WHERE SEATSOCC < F~SEATSMAX
      AND EXISTS ( SELECT * FROM SPFLI
                     WHERE CARRID = F~CARRID
                       AND CONNID = F~CONNID
                       AND CITYFROM = 'FRANKFURT'
                       AND CITYTO = 'NEW YORK' )
      AND FLDATE BETWEEN '19990101' AND '19990331'.
ENDSELECT.
<b>Internal Tables</b>
1.     Table operations should be done using explicit work areas rather than via header lines.
2.     Always try to use binary search instead of linear search. But don’t forget to sort your internal table before that.
3.     A dynamic key access is slower than a static one, since the key specification must be evaluated at runtime.
4.     A binary search using secondary index takes considerably less time.
5.     LOOP ... WHERE is faster than LOOP/CHECK because LOOP ... WHERE evaluates the specified condition internally.
6.     Modifying selected components using “ MODIFY itab …TRANSPORTING f1 f2.. “ accelerates the task of updating  a line of an internal table.
Point # 2
READ TABLE ITAB INTO WA WITH KEY K = 'X‘ BINARY SEARCH.
IS MUCH FASTER THAN USING
READ TABLE ITAB INTO WA WITH KEY K = 'X'.
If TAB has n entries, linear search runs in O( n ) time, whereas binary search takes only O( log2( n ) ).
Point # 3
READ TABLE ITAB INTO WA WITH KEY K = 'X'. IS FASTER THAN USING
READ TABLE ITAB INTO WA WITH KEY (NAME) = 'X'.
Point # 5
LOOP AT ITAB INTO WA WHERE K = 'X'.
ENDLOOP.
The above code is much faster than using
LOOP AT ITAB INTO WA.
  CHECK WA-K = 'X'.
ENDLOOP.
Point # 6
WA-DATE = SY-DATUM.
MODIFY ITAB FROM WA INDEX 1 TRANSPORTING DATE.
The above code is more optimized as compared to
WA-DATE = SY-DATUM.
MODIFY ITAB FROM WA INDEX 1.
7.     Accessing the table entries directly in a "LOOP ... ASSIGNING ..." accelerates the task of updating a set of lines of an internal table considerably
8.    If collect semantics is required, it is always better to use to COLLECT rather than READ BINARY and then ADD.
9.    "APPEND LINES OF itab1 TO itab2" accelerates the task of appending a table to another table considerably as compared to “ LOOP-APPEND-ENDLOOP.”
10.   “DELETE ADJACENT DUPLICATES“ accelerates the task of deleting duplicate entries considerably as compared to “ READ-LOOP-DELETE-ENDLOOP”.
11.   "DELETE itab FROM ... TO ..." accelerates the task of deleting a sequence of lines considerably as compared to “  DO -DELETE-ENDDO”.
Point # 7
Modifying selected components only makes the program faster as compared to Modifying all lines completely.
e.g,
LOOP AT ITAB ASSIGNING <WA>.
  I = SY-TABIX MOD 2.
  IF I = 0.
    <WA>-FLAG = 'X'.
  ENDIF.
ENDLOOP.
The above code works faster as compared to
LOOP AT ITAB INTO WA.
  I = SY-TABIX MOD 2.
  IF I = 0.
    WA-FLAG = 'X'.
    MODIFY ITAB FROM WA.
  ENDIF.
ENDLOOP.
Point # 8
LOOP AT ITAB1 INTO WA1.
  READ TABLE ITAB2 INTO WA2 WITH KEY K = WA1-K BINARY SEARCH.
  IF SY-SUBRC = 0.
    ADD: WA1-VAL1 TO WA2-VAL1,
         WA1-VAL2 TO WA2-VAL2.
    MODIFY ITAB2 FROM WA2 INDEX SY-TABIX TRANSPORTING VAL1 VAL2.
  ELSE.
    INSERT WA1 INTO ITAB2 INDEX SY-TABIX.
  ENDIF.
ENDLOOP.
The above code uses BINARY SEARCH for collect semantics. READ BINARY runs in O( log2(n) ) time. The above piece of code can be more optimized by
LOOP AT ITAB1 INTO WA.
  COLLECT WA INTO ITAB2.
ENDLOOP.
SORT ITAB2 BY K.
COLLECT, however, uses a hash algorithm and is therefore independent
of the number of entries (i.e. O(1)) .
Point # 9
APPEND LINES OF ITAB1 TO ITAB2.
This is more optimized as compared to
LOOP AT ITAB1 INTO WA.
  APPEND WA TO ITAB2.
ENDLOOP.
Point # 10
DELETE ADJACENT DUPLICATES FROM ITAB COMPARING K.
This is much more optimized as compared to
READ TABLE ITAB INDEX 1 INTO PREV_LINE.
LOOP AT ITAB FROM 2 INTO WA.
  IF WA = PREV_LINE.
    DELETE ITAB.
  ELSE.
    PREV_LINE = WA.
  ENDIF.
ENDLOOP.
Point # 11
DELETE ITAB FROM 450 TO 550.
This is much more optimized as compared to
DO 101 TIMES.
  DELETE ITAB INDEX 450.
ENDDO.
12.   Copying internal tables by using “ITAB2[ ] = ITAB1[ ]” as compared to “LOOP-APPEND-ENDLOOP”.
13.   Specify the sort key as restrictively as possible to run the program faster.
Point # 12
ITAB2[] = ITAB1[].
This is much more optimized as compared to
REFRESH ITAB2.
LOOP AT ITAB1 INTO WA.
  APPEND WA TO ITAB2.
ENDLOOP.
Point # 13
“SORT ITAB BY K.” makes the program runs faster as compared to “SORT ITAB.”
Internal Tables         contd…
Hashed and Sorted tables
1.     For single read access hashed tables are more optimized as compared to sorted tables.
2.      For partial sequential access sorted tables are more optimized as compared to hashed tables
Hashed And Sorted Tables
Point # 1
Consider the following example where HTAB is a hashed table and STAB is a sorted table
DO 250 TIMES.
  N = 4 * SY-INDEX.
  READ TABLE HTAB INTO WA WITH TABLE KEY K = N.
  IF SY-SUBRC = 0.
  ENDIF.
ENDDO.
This runs faster for single read access as compared to the following same code for sorted table
DO 250 TIMES.
  N = 4 * SY-INDEX.
  READ TABLE STAB INTO WA WITH TABLE KEY K = N.
  IF SY-SUBRC = 0.
  ENDIF.
ENDDO.
Point # 2
Similarly for Partial Sequential access the STAB runs faster as compared to HTAB
LOOP AT STAB INTO WA WHERE K = SUBKEY.
ENDLOOP.
This runs faster as compared to
LOOP AT HTAB INTO WA WHERE K = SUBKEY.
ENDLOOP.
<b>Reward if usefufll</b>