Allow the Atomic Sum of Different Types

[matekelemen]

AtomicAdd used the same template parameter for both the left and right hand side operands. This PR templates the two operands separately, allowing the left hand side operand's update with a different type.

float target = 0;
double update = 1;
AtomicAdd(target, update);

A use case would be assembly when the local space uses double precision floats while the global space is in single precision.

@reviewers can you please take a close look? I don't think this would be an issue, but I've been wrong about OpenMP before ...

[philbucher]

I feel like it would be cleaner to solve this "client side"

float target = 0;
double update = 1;
AtomicAdd(target, static_case<float>(update));

[matekelemen]

I feel like it would be cleaner to solve this "client side"

float target = 0;
double update = 1;
AtomicAdd(target, static_case<float>(update));

Rust infected you, hasn't it

[philbucher]

I didn't want to write it but yes, it has

It just wont let you do ambiguous stuff, for better or worse...