Mapping global sections on VMS

             +----------------------------------------------+
             |VALUE =  hcreateg(global-name,basecommon,size) |
             +----------------------------------------------+
                                  

Action: Function to create and map a global section .

The function first opens a file with UFO option (using HSTOPEN-GBL), then creates and maps the global section using SYS$CRMPSC. Open the file using SYS$SETDFPROT to set protection loose.

Input parameters:

globalname

Name of the section to be mapped

basecommon

First word of COMMON to be mapped.

size

size of the COMMON in words.

The function value returned is equal to the global section length (pages) if the procedure was successful or an errorcode <0 if an error occurred.

HCREATEG$DIR is a LOGICAL which, if defined, gives the directory for the mapping file of the global section. In this case, the file is not deleted upon closing.

             +----------------------------------------------+
             |VALUE =  hmapg(global-name,base-common,offset) |
             +----------------------------------------------+
                                  

Action: Function to dynamically map to an existing global section.

The function maps to the global section using SYS$MGBLSC, allocating pages in the p0 region with the sec$m_expreg option. 

Input parameters:

globalname

Name of the section to be mapped

basecommon

First word of reference COMMON to be mapped.

offset

Offset with respect to BASECOMMON of the mapped section in words, i.e. BASECOMMON(OFFSET) is the first word.

The function value returned is equal to the global section length (pages) if the procedure was successful or is an errorcode <0 if an error occurred.

             +----------------------------------------------+
             |VALUE =  hfree(global-size,base-common,offset) |
             +----------------------------------------------+
                                  

Action: Function to dynamically delete/unmap global section space using the service SYS$DELTVA.

Input parameters:

globalsize

Size of the section to be freed (pages).

basecommon

First word of reference COMMON.

offset

Offset with respect to BASECOMMON of the mapped section in words, i.e. BASECOMMON(OFFSET) is the first word.

The function value returned is equal to the global section length (pages) if the procedure was successful or is an errorcode <0 if an error occurred. 

Using PAW as a presenter on VMS systems (global section)

[sec:VMPpresenter]

      PROGRAM PRODUCE
      PARAMETER MAXPAGES=100
      COMMON/PAWC/IPAWC(128*MAXPAGES)
      CHARACTER*8 GNAME
      INTEGER*4 HCREATEG
*
      GNAME='GTEST'
      WAIT_TIME=1.
      NUMEVT=1000
*..............           Create Global section
      NPAGES=HCREATEG(GNAME,IPAWC,128*MAXPAGES)
      IF(NPAGES.GT.0) THEN
         PRINT 1000,GNAME
 1000    FORMAT(' Global Section: ',A,' created')
      ELSE
         IERROR=-NPAGES
         PRINT 2000,IERROR
 2000    FORMAT(' Global Section Error', I6)
         GO TO 99
      ENDIF
      CALL HLIMIT(128*NPAGES)
*...............           Book histos.
      CALL HBOOK1(10,'Test1$',50,-4.,4.,0.)
      CALL HBOOK1(20,'Test2$',50,-4.,4.,0.)
*...............           Fill histos.
      DO 20 I=1,NUMEVT
         DO 10 J=1,100
            CALL RANNOR(A,B)
            CALL HFILL(10,A,0.,1.)
            CALL HFILL(20,B,0.,1.)
 10      CONTINUE
        CALL LIB$WAIT(WAIT_TIME)
 20   CONTINUE
*
 99   STOP
      END
$ fort produce
$ link produce,SYS$INPUT/OPTIONS,-
cern$library:packlib/lib,kernlib/lib
PSECT=PAWC,PAGE


    PAW > edit produce
       macro produce ntimes=100
         nt=[ntimes]
         zone 1 2
         histo/plot 10 K
         histo/plot 20 K
       loop:
           histo/plot 10 U
           histo/plot 20 U
           wait ' ' 1
           nt=[nt] -1
           if nt>0 goto loop
       return
    PAW > global GTEST
    PAW > exec produce ntimes=20

 

Figure:  Visualise histograms in global section

In addition to the facilities described in the previous section, the standard version of PAW may be used as an online presenter on VMS systems using the mechanism of global sections. It is possible for two processes to reference the same histograms using global sections. For example, the first process may be a histogram producer (e.g. a monitoring task) and the second process PAW. As the histograms are being gradually filled by the first task, PAW can view them, and even reset them. To use the global sections, it is also necessary to "page align" the common which is in the global section. This is achieved in the "link step" when making the process (see example). The relevant statements are SYS$INPUT/OPTIONS to tell the linker that some options follow the link statement, and PSECT=PAWC,PAGE which is the option to page align the /PAWC/ common.