# CLProgramCreate

Creates an OpenCL program from a source code.

```
int  CLProgramCreate(
   int           context,     // Handle to an OpenCL context
   const string  source       // Source code
   );

```

An overloaded function version creates an OpenCL program and writes compiler messages into the passed string.

```
int  CLProgramCreate(
   int           context,     // Handle to an OpenCL context
   const string  source,      // Source code
   string       &build_log    // A string for receiving the compilation log
   );

```

Parameters

context

[in]  Handle of the OpenCL context.

source

[in]  String with the source code of the OpenCL program.

&build_log

[in]  A string for receiving the OpenCL compiler messages.

Return Value

A handle to an OpenCL object if successful. In case of error -1 is returned. For information about the error, use the [GetLastError()](/en/docs/check/getlasterror) function.

Note

At the moment, the following error codes are used:

- ERR_OPENCL_INVALID_HANDLE – invalid handle to the context OpenCL.
- ERR_INVALID_PARAMETER – invalid string parameter.
- ERR_NOT_ENOUGH_MEMORY – not enough memory to complete operation.
- ERR_OPENCL_PROGRAM_CREATE – internal error of OpenCL or compilation error.

In some graphic cards working with the [double](/en/docs/basis/types/double) type numbers is disabled by default. This can lead to compilation error 5105. To enable support for the double type numbers, please add the following directive to your OpenCL program: [#pragma OPENCL EXTENSION cl_khr_fp64 : enable](https://www.khronos.org/registry/OpenCL/sdk/1.0/docs/man/xhtml/cl_khr_fp64.html).  However if a graphic card doesn't support double, enabling this directive won't be of help.

Example:

```
//+------------------------------------------------------------------+
//| OpenCL kernel                                                    |
//+------------------------------------------------------------------+
const string
cl_src=
       //--- by default some GPU doesn't support doubles
       //--- cl_khr_fp64 directive is used to enable work with doubles
       "#pragma OPENCL EXTENSION cl_khr_fp64 : enable      \r\n"
       //--- OpenCL kernel function
       "__kernel void Test_GPU(__global double *data,      \r\n"
       "                       const    int N,             \r\n"
       "                       const    int total_arrays)  \r\n"
       "  {                                                \r\n"
       "   uint kernel_index=get_global_id(0);             \r\n"
       "   if (kernel_index>total_arrays) return;          \r\n"
       "   uint local_start_offset=kernel_index*N;         \r\n"
       "   for(int i=0; i<N; i++)                          \r\n"
       "     {                                             \r\n"
       "       data[i+local_start_offset] *= 2.0;          \r\n"
       "     }                                             \r\n"
       "  }                                                \r\n";
//+------------------------------------------------------------------+
//| Test_CPU                                                         |
//+------------------------------------------------------------------+
bool Test_CPU(double &data[],const int N,const int id,const int total_arrays)
  {
//--- check array size
   if(ArraySize(data)==0) return(false);
//--- check array index
   if(id>total_arrays) return(false);
//--- calculate local offset for array with index id
   int local_start_offset=id*N;
//--- multiply elements by 2
   for(int i=0; i<N; i++)
     {
      data[i+local_start_offset]*=2.0;
     }
   return true;
  }
//---
#define ARRAY_SIZE   100  // size of the array
#define TOTAL_ARRAYS 5    // total arrays
//--- OpenCL handles
int cl_ctx;  // OpenCL context handle
int cl_prg;  // OpenCL program handle
int cl_krn;  // OpenCL kernel handle
int cl_mem;  // OpenCL buffer handle
//---
double DataArray1[]; // data array for CPU calculation
double DataArray2[]; // data array for GPU calculation
//+------------------------------------------------------------------+
//| Script program start function                                    |
//+------------------------------------------------------------------+
int OnStart()
  {
//--- initialize OpenCL objects
//--- create OpenCL context
   if((cl_ctx=CLContextCreate())==INVALID_HANDLE)
     {
      Print("OpenCL not found. Error=",GetLastError());
      return(1);
     }
//--- create OpenCL program
   if((cl_prg=CLProgramCreate(cl_ctx,cl_src))==INVALID_HANDLE)
     {
      CLContextFree(cl_ctx);
      Print("OpenCL program create failed. Error=",GetLastError());
      return(1);
     }
//--- create OpenCL kernel
   if((cl_krn=CLKernelCreate(cl_prg,"Test_GPU"))==INVALID_HANDLE)
     {
      CLProgramFree(cl_prg);
      CLContextFree(cl_ctx);
      Print("OpenCL kernel create failed. Error=",GetLastError());
      return(1);
     }
//--- create OpenCL buffer
   if((cl_mem=CLBufferCreate(cl_ctx,ARRAY_SIZE*TOTAL_ARRAYS*sizeof(double),CL_MEM_READ_WRITE))==INVALID_HANDLE)
     {
      CLKernelFree(cl_krn);
      CLProgramFree(cl_prg);
      CLContextFree(cl_ctx);
      Print("OpenCL buffer create failed. Error=",GetLastError());
      return(1);
     }
//--- set OpenCL kernel constant parameters
   CLSetKernelArgMem(cl_krn,0,cl_mem);
   CLSetKernelArg(cl_krn,1,ARRAY_SIZE);
   CLSetKernelArg(cl_krn,2,TOTAL_ARRAYS);
//--- prepare data arrays
   ArrayResize(DataArray1,ARRAY_SIZE*TOTAL_ARRAYS);
   ArrayResize(DataArray2,ARRAY_SIZE*TOTAL_ARRAYS);
//--- fill arrays with data
   for(int j=0; j<TOTAL_ARRAYS; j++)
     {
      //--- calculate local start offset for jth array
      uint local_offset=j*ARRAY_SIZE;
      //--- prepare array with index j
      for(int i=0; i<ARRAY_SIZE; i++)
        {
         //--- fill arrays with function MathCos(i+j);
         DataArray1[i+local_offset]=MathCos(i+j);
         DataArray2[i+local_offset]=MathCos(i+j);
        }
     };
//--- test CPU calculation
   for(int j=0; j<TOTAL_ARRAYS; j++)
     {
      //--- calculation of the array with index j
      Test_CPU(DataArray1,ARRAY_SIZE,j,TOTAL_ARRAYS);
     }
//--- prepare CLExecute params
   uint  offset[]={0};
//--- global work size
   uint  work[]={TOTAL_ARRAYS};
//--- write data to OpenCL buffer
   CLBufferWrite(cl_mem,DataArray2);
//--- execute OpenCL kernel
   CLExecute(cl_krn,1,offset,work);
//--- read data from OpenCL buffer
   CLBufferRead(cl_mem,DataArray2);
//--- total error
   double total_error=0;
//--- compare results and calculate error
   for(int j=0; j<TOTAL_ARRAYS; j++)
     {
      //--- calculate local offset for jth array
      uint local_offset=j*ARRAY_SIZE;
      //--- compare the results
      for(int i=0; i<ARRAY_SIZE; i++)
        {
         double v1=DataArray1[i+local_offset];
         double v2=DataArray2[i+local_offset];
         double delta=MathAbs(v2-v1);
         total_error+=delta;
         //--- show first and last arrays
         if((j==0) || (j==TOTAL_ARRAYS-1))
            PrintFormat("array %d of %d, element [%d]:  %f, %f, [error]=%f",j+1,TOTAL_ARRAYS,i,v1,v2,delta);
        }
     }
   PrintFormat("Total error: %f",total_error);
//--- delete OpenCL objects
//--- free OpenCL buffer
   CLBufferFree(cl_mem);
//--- free OpenCL kernel
   CLKernelFree(cl_krn);
//--- free OpenCL program
   CLProgramFree(cl_prg);
//--- free OpenCL context
   CLContextFree(cl_ctx);
//---
   return(0);
  }

```