[QUESTION] Memory Initialization in CVCUDA Test Cases

[Xiaoxuxiaoxu]

Question: Memory Initialization in CVCUDA Test Cases

Issue Description

I was reviewing the test cases in the CVCUDA repository and noticed a potential concern regarding memory initialization. I would like to better understand the design decision behind not explicitly clearing output memory in tests.

Background: CUDA Memory Behavior

As we know, CUDA's official documentation states that:

cudaAlloc does not initialize memory content - it allocates GPU memory with undefined values for performance optimization.

https://docs.nvidia.com/cuda/cuda-runtime-api/group__CUDART__MEMORY.html#group__CUDART__MEMORY_1g37d37965bfb4803b6d4e59ff26856356

In practice, this means:

• Fresh GPU memory (after reset) might contain zeros
• Previously used memory contains residual "dirty data"
• The content is unpredictable and depends on previous allocations

Observed Code Pattern

In test files like tests/cvcuda/system/TestOpFlip.cpp and histogram operator tests, I noticed there's no explicit memory clearing:

// I was expecting to see something like:
// Clear output tensor memory to 0 on the device
ASSERT_EQ(cudaSuccess, cudaMemset(output->basePtr(), 0, outBufSize));

Questions for Clarification

I have a few questions that I hope the community can help clarify:

1. Design Philosophy: Is the absence of explicit cudaMemset intentional to test the operators' robustness against uninitialized memory?

2. Operator Behavior: Do CVCUDA operators guarantee that they'll write to every element in the output buffer, thus eliminating the need for initialization?

3. Edge Cases: Are there any scenarios where operators might not completely overwrite the output buffer, making memory initialization important?

4. Testing Strategy: Is this approach aimed at catching potential bugs where operators inadvertently rely on default memory values?