==== Interfacing with PAPI : Low level interface for Fortran ====
             PROGRAM testpapi
             
             include 'f77papi.h'
             integer check, evntst
             integer*8 t0, t1, c0, c1, value
       
             check = PAPI_NULL
       C
       C     PAPI Initialization
       C
             check = PAPI_VER_CURRENT
             call PAPIF_library_init(check)
             if (check.ne.PAPI_VER_CURRENT) then
                write(6,*) 'PAPI init error'
                write(6,*) '00 check:', check, PAPI_VER_CURRENT
                stop
             endif
       C
       C     PAPI Event Set Creation
       C
             evntst = PAPI_NULL
             call PAPIF_create_eventset(evntst, check)
             if (check.ne.PAPI_OK) then
                write(6,*) 'PAPI event set creation error'
                write(6,*) '01 check:', check, PAPI_OK
                stop
             endif
       C
       C     PAPI Specify a Particular Target Event to Analyze
       C       PAPI_TOT_CYC         Total cycles executed         
       C       PAPI_FP_OPS          Floating point operations executed
       C       PAPI_L1_DCM          Level 1 data cache misses          
       C       PAPI_L2_DCM          Level 2 data cache misses          
       C       for other events see /opt/sw/x86_64/glibc-2.12/ivybridge-ep/papi/5.4.3/gnu-4.4.7/include/papiStdEventDefs.h
       C
             call PAPIF_add_event(evntst, PAPI_FP_OPS, check)
             if (check.ne.PAPI_OK) then
                write(6,*) 'PAPI event set adding error'
                write(6,*) '02 check:', check, PAPI_OK
                stop
             endif
       C
       C     PAPI Time Estimators Initialization                
       C        
             call PAPIF_get_real_usec(t0)
             call PAPIF_get_real_cyc(c0)
       C
       C     PAPI Counting Start                                
       C        
             call PAPIF_start(evntst, check)
             if (check.ne.PAPI_OK) then
                write(6,*) 'PAPI start error !'
                write(6,*) '03 check:', check, PAPI_OK
                stop
             endif
       
       C
       C     *** Here follows the original code section to be analyzed ***
       C
       
       C      
       C     PAPI Counting Stop                                 
       C        
             call PAPIF_stop(evntst, value, check)
             if (check.ne.PAPI_OK) then
                write(6,*) 'PAPI stop error !'
                write(6,*) '04 check:', check, PAPI_OK
                stop
             endif
       C      
       C     PAPI Time Estimators Stop                          
       C        
             call PAPIF_get_real_usec(t1)
             call PAPIF_get_real_cyc(c1)
       C      
       C     PAPI Results                                       
       C        
             write(6,'(a17,8x,i20)') 'PAPI event count ', value
             write(6,'(a25,i20)') 'PAPI time passed in usec ', t1 - t0
             write(6,'(a19,6x,i20)') 'PAPI cycles passed ', c1 - c0
       C      
       C     PAPI Free Event Set                                
       C        
             call PAPIF_cleanup_eventset(evntst, check)
             if (check.ne.PAPI_OK) then
                write(6,*) 'PAPI event set cleanup error !'
                write(6,*) '05 check:', check, PAPI_OK
                stop
             endif
             call PAPIF_destroy_eventset(evntst, check)
             if (check.ne.PAPI_OK) then
                write(6,*) 'PAPI event set destruction error !'
                write(6,*) '06 check:', check, PAPI_OK
                stop
             endif
       C      
       C     PAPI Finalize                                      
       C        
             call PAPIF_shutdown(check)
             if (check.ne.PAPI_OK) then
                write(6,*) 'PAPI finalize failed !'
                write(6,*) '07 check:', check, PAPI_OK
                stop
             endif
             
             END PROGRAM