4 Replies Latest reply on Jan 2, 2010 11:52 AM by jeanluca

    CL_DEVICE_GLOBAL_MEM_SIZE is only 32 bytes



      I've written a small program which determines my platform and shows device info. Here is my platform and device info

      Platform information:
      number of platforms:            1
          name:                        ATI Stream
          vendor:                        Advanced Micro Devices, Inc.
          profile:                    FULL_PROFILE
          version:                    OpenCL 1.0 ATI-Stream-v2.0.0

      Found 1 device

          Intel(R) Atom(TM) CPU Z530   @ 1.60GHz
          CL_DEVICE_MAX_WORK_GROUP_SIZE:            1024
          CL_DEVICE_MAX_COMPUTE_UNITS:            2
          CL_DEVICE_MAX_WORK_ITEM_SIZES:            3
          CL_DEVICE_MAX_WORK_GROUP_SIZE:            1024
          CL_DEVICE_ADDRESS_BITS:                32
          CL_DEVICE_GLOBAL_MEM_SIZE:            32B
          CL_DEVICE_LOCAL_MEM_TYPE:            global
          CL_DEVICE_LOCAL_MEM_SIZE:            32B

      Because the sizes for memory are defined in 'bytes' I've added the 'B'. However 32 is not much, I have a system with 1GB (and not all memory is in use), so shouldn't this value be a little bit more ?

      I guess with a global mem size of 32 bytes you can't do very much Any suggestions how to fix this ?




        • CL_DEVICE_GLOBAL_MEM_SIZE is only 32 bytes

          i think you have error in your code. try  run CLInfo from SDK samples.

            • CL_DEVICE_GLOBAL_MEM_SIZE is only 32 bytes

              you're right, CLInfo gives the right size. I've rewritten my program a little bit


              #include <stddef.h>
              #include <CL/cl.h>
              #include <stdio.h>
              #include <stddef.h>
              #include <stdlib.h>

              int main()

                cl_platform_id clSelectedPlatformID = NULL;
                cl_uint num_platforms ;
                cl_int ciErrNum = clGetPlatformIDs (1,&clSelectedPlatformID, &num_platforms);

                cl_uint ciDeviceCount;
                cl_device_id device_id;             // compute device id
                cl_int  err ;

                err = clGetDeviceIDs(clSelectedPlatformID, CL_DEVICE_TYPE_CPU, 1, &device_id, &ciDeviceCount);
                if ( err != CL_SUCCESS)
                      printf("Error: Failed to create a device group %d!\n", err);
                printf("number of devices %d\n", ciDeviceCount) ;
                size_t local ;
                clGetDeviceInfo(device_id, CL_DEVICE_GLOBAL_MEM_SIZE, sizeof(size_t), &local, NULL);
                printf("\tCL_DEVICE_GLOBAL_MEM_SIZE:\t\t\t%luB\n", local) ;

                return EXIT_SUCCESS ;

              But now it prints a size of 0. Any comments on the program ? Furthermore, if I leave the platformID NULL in clGetDeviceIDs I get an error. The documentation says you can, any thought on this ?



                • CL_DEVICE_GLOBAL_MEM_SIZE is only 32 bytes

                  yes you can. but "If platform is NULL, the behavior is implementation-defined."

                  second you get only one device with that code. you must first get count of device with this

                  clGetDeviceIDs(clSelectedPlatformID, CL_DEVICE_TYPE_ALL, 0, NULL, &ciDeviceCount);

                  then in ciDeviceCount you get how many devices is in system. every GetInfo call can return size if set 0 in param_value_size and NULL in param_value. then functions return count of item or size in bytes.

                    • CL_DEVICE_GLOBAL_MEM_SIZE is only 32 bytes

                      what does 'implementation-defined' mean ?

                      I've fixed the code


                      cl_device_id *devices;
                      if ((devices = (cl_device_id*)malloc(sizeof(cl_device_id) * ciDeviceCount)) == NULL)
                            printf("Failed to allocate memory for devices !!!\n\n") ;
                            exit(EXIT_FAILURE) ;

                        err = clGetDeviceIDs (clSelectedPlatformID, CL_DEVICE_TYPE_ALL, ciDeviceCount, devices, &ciDeviceCount);