[Rcpp-devel] OpenMP and Parallel BLAS

[Balamuta, James Joseph]

Greetings and Salutations,

The answer is yes, multiple processes can concurrently modify different parts of the object. So, the object is not “locked.”

In this case, it’s important to note the scope of the object being “shared” and not “private.”

Also, the object is not being used in any computations that could introduce a race condition.

To confirm, here is a simple test using cores = 1:5 and a matrix of 100 x 100 dimensions:

Unit: milliseconds
expr                 min            lq               mean      median        uq            max         neval
reg              149.16828 150.57064 151.50028 151.14911 151.77306 167.89586   100
omp_1core 148.61683 150.38602 150.97419 150.92021 151.42784 153.87262   100
omp_2core  76.87057  77.67058  78.72599  78.07599  78.75143  88.49076   100
omp_3core  52.86078  53.41599  55.48897  53.81420  56.09687  66.68860   100
omp_4core  40.09745  42.64505  46.52619  44.09979  49.99153  63.37927   100
omp_5core  39.23680  44.04410  46.22926  45.22581  48.45514  51.05932   100

> all.equal(updateImplicitX(test,test,test,test,5),updateImplicitX_p(test,test,test,test,5,3))
[1] TRUE

So, there is ~2x – 3.4x speed up vs. the non-parallel version.

Parallel version using my suggestions and benchmarking…

https://gist.github.com/coatless/5c4f95c69f7a1b61b2a5


Sincerely,

JJB
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