NCA CUDA Programming & Parallel Computing 5

Question 1

Which CUDA profiling tool provides detailed kernel performance metrics such as memory throughput and warp efficiency?

Accepted Answer

Nsight Compute

Answer

Nsight Compute is NVIDIA's kernel-level profiler that reports metrics like memory bandwidth utilization, warp efficiency, and occupancy.

Question 2

What is the difference between cudaMemcpy and cudaMemcpyAsync?

Accepted Answer

cudaMemcpyAsync is non-blocking and can overlap with kernel execution in a stream

Answer

cudaMemcpyAsync returns immediately and can be issued to a stream, enabling overlap with compute or other transfers.

Question 3

Which of the following correctly computes a global thread index for a 1D grid of 1D blocks in CUDA?

Accepted Answer

blockIdx.x * blockDim.x + threadIdx.x

Answer

The standard formula blockIdx.x * blockDim.x + threadIdx.x maps each thread to a unique global index across the entire grid.

Question 4

What happens when a CUDA kernel accesses global memory at an unaligned address?

Accepted Answer

The access may require multiple memory transactions, reducing throughput

Answer

Unaligned global memory access can break coalescing, requiring additional transactions and lowering effective memory bandwidth.

Question 5

What is the purpose of the CUDA occupancy calculator (cudaOccupancyMaxActiveBlocksPerMultiprocessor)?

Accepted Answer

To determine how many blocks can simultaneously run on an SM given resource usage

Answer

This API computes the maximum number of active blocks per SM based on register and shared memory usage of the kernel.

(NCA) NVIDIA-Certified Associate Practice Test