CEERAN0—Calculate uniform random numbers

CEERAN0 generates a sequence of uniform pseudo-random numbers between 0.0 and 1.0 using the multiplicative congruential method with a user-specified seed. The uniform (0,1) pseudo-random numbers are generated using the multiplicative congruential method:

  seed(i) = (950706376 * seed(i-1)) mod 2147483647;

  randomno(i) = seed(i) / 2147483647;


Syntax

>>-CEERAN0--(--seed--,--random_no--,--fc--)--------------------><

seed (input/output)

A fullword binary signed integer representing an initial value used to generate random numbers. seed must be a variable; it cannot be an input-only parameter. The valid range is 0 to +2,147,483,646. If seed equals 0, the seed is generated from the current Greenwich Mean Time. On return to the calling routine, CEERAN0 changes the value of seed so that it can be used as the new seed in the next call.

random_no (output)

An 8-byte double precision floating-point number with a value between 0 and 1, exclusive. If seed is invalid, random_no is set to -1 and CEERAN0 terminates with a non-CEE000 symbolic feedback code.

fc (output)

A 12-byte feedback code, optional in some languages, that indicates the result of this service. If you choose to omit this parameter, refer to Invoking callable services for the appropriate syntax to indicate that the feedback code was omitted.

The following symbolic conditions can result from this service:

Code	Severity	Message number	Message text
CEE000	0	—	The service completed successfully.
CEE2ER	1	2523	The system time was not available when CEERAN0 was called. A seed value of 1 was used to generate a random number and a new seed value.
CEE2ES	3	2524	An invalid seed value was passed to CEERAN0. The random number was set to -1.

Usage notes

z/OS UNIX considerations—In multithread applications, CEERAN0 affects only the calling thread. The seed is unique to the thread.

Examples

Following is an example of CEERAN0 called by C/C++.

/*Module/File Name: EDCRAN0   */

#include <string.h>
#include <stdio.h>
#include <leawi.h>
#include <stdlib.h>
#include <ceeedcct.h>

int main (void) {

   _INT4 seed;
   _FLOAT8 random;
   _FEEDBACK fc;
   int number;

   seed = 0;
   CEERAN0(&seed,&random,&fc);
   if ( _FBCHECK ( fc , CEE000 ) != 0 ) {
      printf("CEERAN0 failed with message number %d\n",
             fc.tok_msgno);
      exit(2999);
   }
   number = random * 1000;
   printf("The 3 digit random number is %d\n",number);
}

Following is an example of CEERAN0 called by COBOL.

CBL LIB,QUOTE
      *Module/File Name: IGZTRAN0
      ************************************************
      ** CBLRAN0 - Call CEERAN0 to generate uniform **
      **                     random numbers         **
      ************************************************
       IDENTIFICATION DIVISION.
       PROGRAM-ID. CBLRAN0.
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01  SEED                    PIC S9(9) BINARY.
       01  RANDNUM                 COMP-2.
       01  FC.
           02  Condition-Token-Value.
           COPY  CEEIGZCT.
               03  Case-1-Condition-ID.
                   04  Severity    PIC S9(4) BINARY.
                   04  Msg-No      PIC S9(4) BINARY.
               03  Case-2-Condition-ID
                         REDEFINES Case-1-Condition-ID.
                   04  Class-Code  PIC S9(4) BINARY.
                   04  Cause-Code  PIC S9(4) BINARY.
               03  Case-Sev-Ctl    PIC X.
               03  Facility-ID     PIC XXX.
           02  I-S-Info            PIC S9(9) BINARY.

       PROCEDURE DIVISION.

       PARA-CBLRAN0.
      ************************************************
      ** Specify 0 for SEED, so the seed will be
      ** derived from the current Greenwich Mean Time
      ************************************************
           MOVE 0 TO SEED.
      ************************************************
      ** Call CEERAN0 to return random number between
      **     0.0 and 1.0
      ************************************************
           CALL "CEERAN0" USING SEED , RANDNUM , FC.
      ************************************************
      ** If CEERAN0 runs successfully, display result.
      ************************************************
           IF CEE000 of FC  THEN
               DISPLAY "The random number is: " RANDNUM
           ELSE
               DISPLAY "CEERAN0 failed with msg "
                   Msg-No of FC UPON CONSOLE
               STOP RUN
           END-IF.
           GOBACK.

Following is an example of CEERAN0 called by PL/I.

*PROCESS MACRO;
 /* Module/File Name: IBMRAN0                        */
 /****************************************************/
 /**                                                **/
 /** Function: CEERAN0 - calculate uniform random   **/
 /** numbers                                        **/
 /**                                                **/
 /****************************************************/
 PLIRAN0: PROC OPTIONS(MAIN);

    %INCLUDE  CEEIBMAW;
    %INCLUDE  CEEIBMCT;

    DCL SEED     REAL FIXED BINARY(31,0);
    DCL RANDNUM  REAL FLOAT DECIMAL(16);
    DCL 01 FC,                     /* Feedback token */
           03 MsgSev    REAL FIXED BINARY(15,0),
           03 MsgNo     REAL FIXED BINARY(15,0),
           03 Flags,
              05 Case      BIT(2),
              05 Severity  BIT(3),
              05 Control   BIT(3),
           03 FacID     CHAR(3),      /* Facility ID */
           03 ISI   /* Instance-Specific Information */
                        REAL FIXED BINARY(31,0);

    SEED = 7; /* Specify an integer as the initial   */
              /* value used to calculate the random  */
              /* numbers                             */


   /* Call CEERAN0 to generate random number between */
   /*    0.0 and 1.0                                 */
    CALL CEERAN0 ( SEED, RANDNUM, FC );

    IF  FBCHECK( FC, CEE000)  THEN  DO;
       PUT SKIP LIST ( 'The random number is '
          || RANDNUM );
       END;
    ELSE  DO;
       DISPLAY( 'CEERAN0 failed with msg '
          || FC.MsgNo );
       STOP;
       END;

 END PLIRAN0;