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query a matrix, vector, or scalar if GrB_wait will do anything to it #75
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I think adding this functionality is a good idea. As I understand, what you're essentially asking is whether the function call
GrB_Wait(A, GrB_COMPLETE)would return immediately?Given the API already includes the term "complete" for this, you might also consider
GrB_Is_completeorGrB_Is_readyas names.Another bit of prior art to consider is the syntax used by futures, including C++'s
std::future.std::futurehaswaitandwait_for, which waits for a certain period of time. Many other C++ future implementations, including my BCL implementations, haveis_ready()orcheck()methods that immediately return a boolean value.- I want an API that minimizes cognitive load on our users. Hence, something closely aligned with what we have already make sense. We already have GrB_wait(A, GrB_COMPLETE). This returns once A is in the state GrB_COMPLETE). I suggest a perturbation of that: GrB_test_wait(A, GrB_COMPLETE) This function always returns immediately. The return value will tell you if its COMPLETE or not. This name is easier for a programmer working with GraphBLAS to remember since it’s a slight perturbation from an existing function.…--Tim
GrB_MATERIALIZE, you mean? That's what I want to test. I want to query in O(1) time without any change to the matrix A ifGrB_wait (A, GrB_MATERIALIZE)would do anything to the matrix A.GrB_wait (A, GrB_COMPLETE)only means "A is ready to pass to another thread". It doesn't mean that A contains no pending work. Thread 1 can pass a matrix to thread 2, and safely leave work in the matrix A for thread 2 to do. That's whatGrB_wait (A, GrB_COMPLETE), means, if thread 1 does it.Currently, my
GrB_wait (A, GrB_COMPLETE)only does one thing:#pragma omp flush. Nothing else.I don't need a
GrB_test_wait (A, GrB_COMPLETE), but I suppose that's useful. Better would be the syntax:GrB_Info GrB_test_wait (GrB_Matrix A, GrB_WaitMode mode, bool &result) ;
and result would be true if GrB_wait (A, mode) would do nothing, or false if GrB_wait (A,mode) has work to do.If there were a
GrB_test_wait (A, GrB_COMPLETE, &result), then I guess I would have to keep track of whether or not#pragma omp flushhas been on on the thread that wrote to the matrix? Seems awkward. I don't keep that state inside matrix.
RedisGraph requires a method to query a matrix, vector, or scalar to see if it has any pending operations. That is, it returns true
Roi (@swilly22) has one solution: DrTimothyAldenDavis/GraphBLAS#172 . This proposed method has signature (for the GrB_Matrix case):
GrB_Info GxB_Matrix_pending (GrB_Matrix A, bool *has_pending_operations) ;An alternative would be to include this query in GrB_get, as the _Generic signature:
GrB_Info GrB_get (GrB_Matrix A, GrB_Something whatever, bool *has_pending_operations) ;where "whatever" would be an enum value like "GrB_PENDING" or "GrB_WILL_WAIT" or whatever.
Any thoughts? Can you consider this for the v2.1 C API?