From: eregontp@... Date: 2017-02-28T20:47:08+00:00 Subject: [ruby-core:79826] [Ruby trunk Feature#12901] Anonymous functions without scope lookup overhead Issue #12901 has been updated by Benoit Daloze. Shyouhei Urabe wrote: > I think it's impossible to optimize lambdas without breaking backwards compatibility. It is possible with deoptimization though. An optimizer might assume that a block does not call binding and in case it does, deoptimize. Removing the scope lookup overhead for accessing captured variables is possible if one considers a whole method containing the lambda for analysis. However, it seems much harder to optimize the scope lookup for a lambda capturing a non-optimized scope. I do not think scope lookup is the only overhead of lambdas though, there is a lot of implicitly captured state which needs to be restored for every call (but the same optimizations apply when optimizing a method containing the lambda). ---------------------------------------- Feature #12901: Anonymous functions without scope lookup overhead https://bugs.ruby-lang.org/issues/12901#change-63261 * Author: Richard Schneeman * Status: Open * Priority: Normal * Assignee: * Target version: ---------------------------------------- Right now if you are writing performance sensitive code you can get a performance bump by not using anonymous functions (procs, lambdas, blocks) due to the scope lookup overhead. https://twitter.com/apotonick/status/791167782532493312?lang=en I would like to be able to create an anonymous function and specify I don't need it to perform the lookup when called. I am thinking that this code: ~~~ Proc.new(scope: false) {|var| puts var } ~~~ Would be the equivalent of ~~~ def anon(var) puts var end ~~~ If you call it while trying to access something from outside of the scope it would error ~~~ var = "hello" Proc.new(scope: false) { puts var }.call # => NameError: undefined local variable or method `var' for main:Object ~~~ An example of a case where this could be used is found in https://github.com/rails/sprockets/pull/417. In this case we are getting rid of anonymous functions in favor of a method created with refinements. This solution works but it was not an obvious optimization. It would be convenient to have a syntax for defining anonymous functions that do not need access to caller scope. -- https://bugs.ruby-lang.org/ Unsubscribe: