/*

 * This example shows how to use PAPI_library_init, PAPI_create_eventset,

 * PAPI_add_event, * PAPI_start and PAPI_stop.  These 5 functions 

 * will allow a user to do most of the performance information gathering

 * that they would need. PAPI_read could also be used if you don't want

 * to stop the EventSet from running but only check the counts.

 *

 * Also, we will use PAPI_perror for * error information.

 *

 * In addition, a new call was created called PAPI_add_env_event

 * that allows a user to setup environment variable to read 

 * which event should be monitored this allows different events

 * to be monitored at runtime without recompiling, the syntax

 * is as follows:

 * PAPI_add_env_event(int *EventSet, int *Event, char *env_variable);

 * EventSet is the same as in PAPI_add_event

 * Event is the default event to monitor if the environment variable

 *       does not exist and differs from PAPI_add_event as it is

 *       a pointer.

 * env_varialbe is the name of the environment variable to look for

 *       the event code, this can be a name, number or hex, for example

 *       PAPI_L1_DCM could be defined in the environment variable as

 *       all of the following:  PAPI_L1_DCM, 0x80000000, or -2147483648

 *

 * To use only add_event you would change the calls to 

 * PAPI_add_env_event(int *EventSet, int *Event, char *env_variable);

 * to PAPI_add_event(int *EventSet, int Event);

 *

 * We will also use PAPI_event_code_to_name since the event may have

 * changed.

 * Author: Kevin London 

 * email:  london@cs.utk.edu

 */

#include <stdio.h>

#include <stdlib.h>

#include "papi.h" /* This needs to be included anytime you use PAPI */

int PAPI_add_env_event(int *EventSet, int *Event, char *env_variable);

int main(){

  int retval,i;

  int EventSet=PAPI_NULL;

  int event_code=PAPI_TOT_INS; /* By default monitor total instructions */

  char errstring[PAPI_MAX_STR_LEN];

  char event_name[PAPI_MAX_STR_LEN];

  float a[1000],b[1000],c[1000];

  long long values;

  /* This initializes the library and checks the version number of the

   * header file, to the version of the library, if these don't match

   * then it is likely that PAPI won't work correctly.  

   */

  if ((retval = PAPI_library_init(PAPI_VER_CURRENT)) != PAPI_VER_CURRENT ){

	/* This call loads up what the error means into errstring 

	 * if retval == PAPI_ESYS then it might be beneficial

 	 * to call perror as well to see what system call failed

	 */

	PAPI_perror("PAPI_library_init");

	exit(-1);

  }

  /* Create space for the EventSet */

  if ( (retval=PAPI_create_eventset( &EventSet ))!=PAPI_OK){

	PAPI_perror(retval, errstring, PAPI_MAX_STR_LEN);

        exit(-1);

  }

  /*  After this call if the environment variable PAPI_EVENT is set,

   *  event_code may contain something different than total instructions.

   */

  if ( (retval=PAPI_add_env_event(&EventSet, &event_code, "PAPI_EVENT"))!=PAPI_OK){

        PAPI_perror("PAPI_add_env_event");

        exit(-1);

  }

  /* Now lets start counting */

  if ( (retval = PAPI_start(EventSet)) != PAPI_OK ){

        PAPI_perror("PAPI_start");

        exit(-1);

  }

  /* Some work to take up some time, the PAPI_start/PAPI_stop (and/or

   * PAPI_read) should surround what you want to monitor.

   */

  for ( i=0;i<1000;i++){

        a[i] = b[i]-c[i];

        c[i] = a[i]*1.2;

  }

  if ( (retval = PAPI_stop(EventSet, &values) ) != PAPI_OK ){

        PAPI_perror("PAPI_stop");

        exit(-1);

  }

  if ( (retval=PAPI_event_code_to_name( event_code, event_name))!=PAPI_OK){

        PAPI_perror("PAPI_event_code_to_name");   

        exit(-1);

  }

  printf("Ending values for %s: %lld\n", event_name,values);

  /* Remove PAPI instrumentation, this is necessary on platforms

   * that need to release shared memory segments and is always

   * good practice.

   */

  PAPI_shutdown();

  exit(0);

}

int PAPI_add_env_event(int *EventSet, int *EventCode, char *env_variable){

  int real_event=*EventCode;

  char *eventname;

  int retval;

  if ( env_variable != NULL ){

    if ( (eventname=getenv(env_variable)) ) {

        if ( eventname[0] == 'P' ) {  /* Use the PAPI name */

           retval=PAPI_event_name_to_code(eventname, &real_event );

           if ( retval != PAPI_OK ) real_event = *EventCode;

        }

        else{

           if ( strlen(eventname)>1 && eventname[1]=='x')

                sscanf(eventname, "%#x", &real_event);

           else

               real_event = atoi(eventname);

        }

    }

  }

  if ( (retval = PAPI_add_event( *EventSet, real_event))!= PAPI_OK ){

        if ( real_event != *EventCode ) {

                if ( (retval = PAPI_add_event( *EventSet, *EventCode)) == PAPI_OK

){

                        real_event = *EventCode;

                }

        }

  }

  *EventCode = real_event;

  return retval;

}