cobol - 尽管种子不同，随机函数总是返回相同的结果

Question

我正在尝试创建一个随机数生成器（一些随机数稍后将被转换为 [AZ] 字符）。我已经让随机生成器的主要部分正常工作，但我不断收到相同的随机结果0.6734141422。

我面临的另一个问题：有一半时间我的程序编译速度太快。由于我以毫秒为单位使用当前日期，因此快速编译我的程序将意味着为RANDOM函数提供相同的种子。我一直在考虑简单地添加一个计数器，在将每个种子应用到RANDOM. 这足够还是有更优雅的解决方案？

有人可以向我解释为什么即使应用了不同的种子值，我总是会收到相同的随机结果？每次执行程序时都会得到这个结果。

我正在使用 PerCobol 编译器，据我所知，它与 OpenCobol 兼容。

总结一下：

我应该如何克服平等的种子？

为什么我会收到不同种子的相同随机结果？

000100 IDENTIFICATION DIVISION.
000200 PROGRAM-ID. RandomTest.

ENVIRONMENT DIVISION.  

   DATA DIVISION.
   WORKING-STORAGE SECTION.
   01 RANDOMRESULT PIC S9V9(10).

   01 WS-CURRENT-DATE-DATA.
    05 WS-CURRENT-DATE.
      10 WS-CURRENT-YEAR    PIC 9(04).
      10 WS-CURRENT-MONTH   PIC 9(02).
      10  WS-CURRENT-DAY    PIC 9(02).
    05  WS-CURRENT-TIME.
  10  WS-CURRENT-HOURS      PIC 9(02).
  10  WS-CURRENT-MINUTE     PIC 9(02).
  10  WS-CURRENT-SECOND     PIC 9(02).
  10  WS-CURRENT-MILLISECONDS   COMP-2.
05  WS-DIFF-FROM-GMT        PIC S9(04).

   PROCEDURE DIVISION.
   PRGRM.

   PERFORM 4 TIMES
    MOVE FUNCTION CURRENT-DATE TO WS-CURRENT-DATE-DATA
    COMPUTE RANDOMRESULT = FUNCTION RANDOM (WS-CURRENT-MILLISECONDS)
    DISPLAY "Seed value: " WS-CURRENT-MILLISECONDS UPON SYSOUT
    DISPLAY "Random result: " RANDOMRESULT UPON SYSOUT
   END-PERFORM

   STOP RUN.

样本输出：

Seed value: 8.222829361429599E-67
Random result: 0.6734141422
Seed value: 8.964670591567083E-67
Random result: 0.6734141422
Seed value: 9.335591206635825E-67
Random result: 0.6734141422
Seed value: 9.335591206635825E-67
Random result: 0.6734141422

如果您对解决我最初的问题有建议（创建一个由字母数字字符组成的随机密码），我也很高兴听到它。

编辑：通过省略种子，两个问题都立即得到解决。这个结论背后的更多信息可以在下面的评论中找到。如果有人解释为什么不同的种子仍然会产生相同的值，我会很高兴听到它！

score 2 · Accepted Answer

是的，你的种子需要是一个整数，所以你不能使用 COMP-2。种子不需要是特定的大小，只是一个整数，你可以把它做得很大。

您的程序编译所花费的时间与任何事情无关。

您应该在第一次调用该函数时指定 SEED。之后，使用零。这将遵循“伪随机”序列。您不需要每次都“播种”，因此无需担心毫秒。

您应该始终输出您的种子，以便以后可以重新生成序列。使用时间变得很棘手，所以取而代之的是一个参数或一个包含种子的单记录文件。

score 1 · Accepted Answer

从这篇文章看来，该函数似乎RANDOM需要一个 32 位整数作为种子。但是，您声明WS-CURRENT-MILLISECONDS为COMP-2浮点数（在其他语言中，为 64 位双精度数）。

我想这要么使它成为种子的无效参数，因此使用默认的种子值 0，或者只使用双精度的第一个或最后 32 位，所以你基本上得到尾数或有效数的一部分这与您尝试的数字相同。

如果发生第一件事，请尝试使用 0 作为种子，我想您会得到相同的输出。在任何情况下，您都可以尝试显式地使用一些不同的整数播种，然后看看会发生什么。

score 0 · Accepted Answer

这是一些生成随机数的源代码，希望对您有所帮助。

   IDENTIFICATION DIVISION.
   PROGRAM-ID.  RANDGEN as "ConsoleApplication2.RANDGEN".
   AUTHOR.  Myron D Denson.
   DATE-COMPILED.
  * ************************************************************** 
  *  SUBROUTINE TO GENERATE RANDOM NUMBERS THAT ARE GREATER THAN
  *    ZERO AND LESS OR EQUAL TO THE RANDOM NUMBERS NEEDED WITH NO
  *    DUPLICATIONS.  (CALL "RANDGEN" USING RANDGEN-AREA.)
  *     
  *    FORMULA CYCLES THROUGH EVERY NUMBER OF 2X2 ONLY ONCE. 
  *    RANDOM-NUMBERS FROM 1 TO RANDOM-NUMBERS-NEEDED ARE CREATED 
  *    AND PASSED BACK TO YOU.
  *
  *  RULES TO USE RANDGEN:
  *
  *    RANDOM-NUMBERS-NEEDED > ZERO 
  *     
  *    COUNT-OF-ACCESSES MUST = ZERO FIRST TIME USED.
  *         
  *    RANDOM-NUMBER = ZERO, WILL BUILD A SEED FOR YOU
  *    WHEN COUNT-OF-ACCESSES IS ALSO = 0 
  *     
  *    RANDOM-NUMBER NOT = ZERO, WILL BE NEXT SEED FOR RANDGEN
  *    YOU CAN PASS RANDGEN YOUR OWN RANDOM-NUMBER SEED
  *     THE FIRST TIME YOU USE RANDGEN.
  *     
  *    BY PLACING A NUMBER IN RANDOM-NUMBER FIELD
  *      THAT FOLLOWES THESE SIMPLE RULES:
  *        IF COUNT-OF-ACCESSES = ZERO AND 
  *        RANDOM-NUMBER > ZERO. 
  *    
  *    YOU CAN PICK THE SEED OR YOU CAN LET RANDGEN BUILD A SEED FOR YOU.
  *
  *       IF YOU PICK A SEED < RANDON-NUMBERS-NEEDED IT WILL BECOME THE LAST
  *          RANDON-NUMBER YOU RECEIVE BACK.
  *       IF SEED > RANDON-NUMBERS-NEEDED LAST NUMBER COULD BE ANYTHING.         
  *     
  *      THAT FOLLOWES THESE SIMPLE RULES:
  *        IF COUNT-OF-ACCESSES = ZERO AND 
  *        RANDOM-NUMBER = ZERO AND 
  *        RANDOM-NUMBER-NEEDED > ZERO  
  *         
  *     TO INSURING A DIFFERENT PATTERN OF RANDOM NUMBERS
  *        A LOW-RANGE AND HIGH-RANGE IS USED TO BUILD
  *        RANDOM NUMBERS.
  *        COMPUTE LOW-RANGE =
  *             ((SECONDS + HOURS + MINUTES + MS) * 1753).           
  *        A HIGH-RANGE = RANDOM-NUMBERS-NEEDED + LOW-RANGE
  *        AFTER RANDOM-NUMBER-BUILT IS CREATED 
  *        AND IS BETWEEN LOW AND HIGH RANGE
  *        RANDUM-NUMBER = RANDOM-NUMBER-BUILT - LOW-RANGE
  *               
  * **************************************************************         
   ENVIRONMENT DIVISION.
   INPUT-OUTPUT SECTION.
   FILE-CONTROL.
   DATA DIVISION.
   FILE SECTION.
   WORKING-STORAGE SECTION.
   01  WORK-AREA.
       05  X2-POWER                     PIC 9      VALUE 2. 
       05  2X2                          PIC 9(12)  VALUE 2.
       05  RANDOM-NUMBER-BUILT          PIC 9(12)  COMP.
       05  FIRST-PART                   PIC 9(12)  COMP.
       05  NOT-USED-NUMBER              PIC 9(12)  COMP.
       05  LOW-RANGE                    PIC 9(12)  VALUE ZERO.
       05  HIGH-RANGE                   PIC 9(12)  VALUE ZERO.
       05  YOU-PROVIDE-SEED             PIC X      VALUE SPACE.
       05  RUN-AGAIN                    PIC X      VALUE SPACE.
       05  PAUSE-FOR-A-SECOND           PIC X      VALUE SPACE.   
   01  SEED-TIME.
       05  HOURS                        PIC 99.
       05  MINUTES                      PIC 99.
       05  SECONDS                      PIC 99.
       05  MS                           PIC 99. 
  *
  * LINKAGE SECTION.
  *  Not used during testing  
   01  RANDGEN-AREA.
       05  COUNT-OF-ACCESSES            PIC 9(12) VALUE ZERO.
       05  RANDOM-NUMBERS-NEEDED        PIC 9(12) VALUE ZERO.
       05  RANDOM-NUMBER                PIC 9(12) VALUE ZERO.
       05  RANDOM-MSG                   PIC X(60) VALUE SPACE.
  *    
  * PROCEDURE DIVISION USING RANDGEN-AREA.
  * Not used during testing 
  *  
   PROCEDURE DIVISION.
   100-RANDGEN-EDIT-HOUSEKEEPING.
       MOVE SPACE TO RANDOM-MSG. 
       IF RANDOM-NUMBERS-NEEDED = ZERO
         DISPLAY 'RANDOM-NUMBERS-NEEDED ' NO ADVANCING
         ACCEPT RANDOM-NUMBERS-NEEDED.
       IF RANDOM-NUMBERS-NEEDED NOT NUMERIC 
         MOVE 'RANDOM-NUMBERS-NEEDED NOT NUMERIC' TO RANDOM-MSG
           GO TO 900-EXIT-RANDGEN.
       IF RANDOM-NUMBERS-NEEDED = ZERO
         MOVE 'RANDOM-NUMBERS-NEEDED = ZERO' TO RANDOM-MSG
           GO TO 900-EXIT-RANDGEN.
       IF COUNT-OF-ACCESSES NOT NUMERIC
         MOVE 'COUNT-OF-ACCESSES NOT NUMERIC' TO RANDOM-MSG
           GO TO 900-EXIT-RANDGEN.
       IF COUNT-OF-ACCESSES GREATER THAN RANDOM-NUMBERS-NEEDED
         MOVE 'COUNT-OF-ACCESSES > THAT RANDOM-NUMBERS-NEEDED' TO RANDOM-MSG
           GO TO 900-EXIT-RANDGEN.
       IF YOU-PROVIDE-SEED = SPACE AND RANDOM-NUMBER = ZERO
         DISPLAY 'DO YOU WANT TO PROVIDE SEED  Y OR N: '
           NO ADVANCING
           ACCEPT YOU-PROVIDE-SEED.  
       IF RANDOM-NUMBER = ZERO AND
          (YOU-PROVIDE-SEED = 'Y' OR 'y')
         DISPLAY 'ENTER SEED ' NO ADVANCING
         ACCEPT RANDOM-NUMBER. 
       IF RANDOM-NUMBER NOT NUMERIC
         MOVE 'RANDOM-NUMBER NOT NUMERIC' TO RANDOM-MSG
         GO TO 900-EXIT-RANDGEN.
   200-RANDGEN-DATA-HOUSEKEEPING.      
       MOVE FUNCTION CURRENT-DATE (9:8) TO SEED-TIME.
       IF COUNT-OF-ACCESSES = ZERO
         COMPUTE LOW-RANGE =
                ((SECONDS + HOURS + MINUTES + MS) * 1753).
       COMPUTE RANDOM-NUMBER-BUILT = RANDOM-NUMBER + LOW-RANGE.  
       COMPUTE HIGH-RANGE = RANDOM-NUMBERS-NEEDED + LOW-RANGE.
       MOVE X2-POWER TO 2X2.             
   300-SET-2X2-DIVISOR.
       IF 2X2 < (HIGH-RANGE + 1) 
          COMPUTE 2X2 = 2X2 * X2-POWER
           GO TO 300-SET-2X2-DIVISOR.    
  * *********************************************************         
  *  IF FIRST TIME THROUGH AND YOU WANT TO BUILD A SEED.    *
  * ********************************************************* 
       IF COUNT-OF-ACCESSES = ZERO AND RANDOM-NUMBER = ZERO
          COMPUTE RANDOM-NUMBER-BUILT =
                ((SECONDS + HOURS + MINUTES + MS) + HIGH-RANGE).
  * *********************************************     
  *    END OF BUILDING A SEED IF YOU WANTED TO  * 
  * ********************************************* 
  * *******************************************************
  * THE NEXT 4 LINE OF CODE ARE FOR TESTING  ON CONSOLE   *  
  * *******************************************************            
  *    IF COUNT-OF-ACCESSES = ZERO        
  *      DISPLAY 'SEED TIME ' SEED-TIME 
  *            ' RANDOM-NUMBER-BUILT ' RANDOM-NUMBER-BUILT 
  *            ' LOW-RANGE  ' LOW-RANGE.          
  * ***************************************************
  * THIS PROCESS IS WHERE THE RANDOM-NUMBER IS BUILT  *  
  * ***************************************************   
   400-RANDGEN-FORMULA.
       COMPUTE FIRST-PART = (5 * RANDOM-NUMBER-BUILT) + 7.
       DIVIDE FIRST-PART BY 2X2 GIVING NOT-USED-NUMBER 
         REMAINDER RANDOM-NUMBER-BUILT. 
       IF RANDOM-NUMBER-BUILT > LOW-RANGE AND
          RANDOM-NUMBER-BUILT < (HIGH-RANGE + 1)
         GO TO 600-RANDGEN-CLEANUP.
       GO TO 400-RANDGEN-FORMULA.
  * *********************************************     
  *    GOOD RANDOM NUMBER HAS BEEN BUILT        *               
  * *********************************************
   600-RANDGEN-CLEANUP.
       ADD 1 TO COUNT-OF-ACCESSES.
       COMPUTE RANDOM-NUMBER = 
            RANDOM-NUMBER-BUILT - LOW-RANGE. 
  * *******************************************************
  * THE NEXT 3 LINE OF CODE ARE FOR TESTING  ON CONSOLE   *  
  * *******************************************************
       DISPLAY RANDOM-NUMBER.
       IF COUNT-OF-ACCESSES < RANDOM-NUMBERS-NEEDED
        GO TO 100-RANDGEN-EDIT-HOUSEKEEPING.     
   900-EXIT-RANDGEN.
       IF RANDOM-MSG NOT = SPACE
        DISPLAY 'RANDOM-MSG: ' RANDOM-MSG.
        MOVE ZERO TO COUNT-OF-ACCESSES RANDOM-NUMBERS-NEEDED RANDOM-NUMBER. 
        MOVE SPACE TO YOU-PROVIDE-SEED RUN-AGAIN.
       DISPLAY 'RUN AGAIN Y OR N '
         NO ADVANCING.
       ACCEPT RUN-AGAIN.
       IF (RUN-AGAIN = 'Y' OR 'y')
         GO TO 100-RANDGEN-EDIT-HOUSEKEEPING.
       ACCEPT PAUSE-FOR-A-SECOND.
       GOBACK.

cobol - 尽管种子不同，随机函数总是返回相同的结果

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