[Rd] Parallel R expression evaluations

Simon Urbanek simon.urbanek at r-project.org
Mon Oct 21 02:24:22 CEST 2013


On Oct 19, 2013, at 1:37 AM, JaiReddy wrote:

> Thanks Simon.
> May I know how R works if two expressions come at the same time for
> evaluation. When I debug my case I found that issue was found with indexed
> values of protected items. 
> As R is single threaded engine, I just want to know how does R behave when
> 2nd expression comes for parsing and evaluation even before 1st expression
> evaluation does complete?

As I said, no API calls may be performed in parallel, that includes parsing and evaluation. Typically, R is run in a sequential loop: read, parse, eval, print so anything that is not processed is blocked until the loop is back to reading. However, given that R can be called from arbitrary front-ends, it's really up to the front-end to decide what to do - as long as it serializes the calls appropriately.


> Thanks
> Jai
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