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Software Technology Tips

1. Who can start CUDA programming?

- Any one who has some basicknowledge on C programming. No prior knowledge of graphics programming.

- CUDA is C with minimal extension and some restrictions.( CUDA is C for GPU)

2. If you have a algo that you want to write in CUDA then follow the below steps.

3. Start writing your algo in C/C++.

4. Changing your implemented C/C++ program according to CUDA requirements.

5. The basic diagram for CUDA code implementation as:

Allocate CPU memory >> Allocate same amount of GPU memory >> take data input in CPU memory >> copy data into GPU memory >> doing processing in GPU memory >> copying final data

in CPU memory.

6. Explainig simple example that calculate cosine of range 0 to 1024.

7. C implementation of algo.

void vcos( int n, float* x, float* y )
        {
           for ( int i = 0; i < n; ++i)
               y[i] = cos( x[i] );
         }

    int main()
       {
   float *host_x, *host_y;

    int n = 1024;
           host_x = (float*)malloc( n*sizeof(float) );
           host_y = (float*)malloc( n*sizeof(float) );

    for( int i = 0; i < 1024; ++i )
        host_x[i] = (float)i;

           vcos( n, host_x, host_y );
                  free(host_x);
                  free(host_y);

      return( 0 );
}

8 . CUDA implementation of Same algo( what should be minimal changes in C code. )

          __global__ void vcos( int n, float* x, float* y )
        {
           int i = blockIdx.x * blockDim.x + threadIdx.x;

y[i] = cos( x[i] );
}

    int main()
       {
   float *host_x, *host_y;
   float *dev_x, *dev_y;
   int n = 1024;

     host_x = (float*)malloc( n*sizeof(float) );
          host_y = (float*)malloc( n*sizeof(float) );
   cudaMalloc( &dev_x, n*sizeof(float) );
          cudaMalloc( &dev_y, n*sizeof(float) );

for( int i = 0; i < 1024; ++i )
host_x[i] = (float) i;

/* fill host_x[i] with data here */

cudaMemcpy( dev_x, host_x, n*sizeof(float), cudaMemcpyHostToDevice );

/* launch 1 thread per vector-element, 256 threads per block */

bk = (int)( n / 256 );
vcos<<<bk,256>>>( n, dev_x, dev_y );

cudaMemcpy( host_y, dev_y, n*sizeof(float), cudaMemcpyDeviceToHost );

/* host_y now contains cos(x) data */

                free(host_x);
                free(host_y);
                cudaFree(dev_x);
                cudaFree(dev_y);

return( 0 );
}

Related Tags:
C, CUDA

Author: Kundan Kumar

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