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cudaexterngpu-shared-memory

Square brackets after float4 vector type

I'm studying a CUDA tutorial and at a some point the shared memory is dynamically allocated like so:

extern __shared__ float4[] buffer;

It seems to be quite simple to understand except for the square brackets [] after the vector type float4. What do they mean? why should I write them?

Solution

  • This is used for a dynamic shared memory and the proper way is :

    extern __shared__ float4 buffer[]

    , not

    extern __shared__ float4[] buffer

    When you use this ,you must also use the size of the allocated memory in the kernel call:

    size_t blockSize = theBlockSize * theBlockSize
myfunc<<< NbBlocks, NbThreadsPerBlock , sizeof(float4) * blockSize>>>