Always use type-appropriate mechanisms to represent the absence of a value. For objects, use default constructors rather than nullptr. For potentially absent values, consider using optional types. For pointers, use null checks before performing operations on them. Examples: - INCORRECT: `bias_md = nullptr;` when `bias_md` is an object type (dnnl::memory::desc) - CORRECT: `bias_md = dnnl::memory::desc();` to represent an "empty" descriptor - INCORRECT: `ncclHeartbeatMonitorThread_ = std::thread(...);` without checking current state - CORRECT: ```cpp // Check nullness before assignment to prevent issues on second call if (!ncclHeartbeatMonitorThread_.joinable()) { ncclHeartbeatMonitorThread_ = std::thread(...); } ``` This practice improves type safety, prevents null pointer dereferences, and creates more maintainable code by using language features designed for representing absence of values.