I was learning hadoop, I found number of reducers very confusing : 1) Number of reducers is same as number of partitions. 2) Number of reducers is 0.95 or 1.75 multiplied by (no. of nodes) * (no....

Currently I am working on FCC Game of Life and I was able figure out how to generate the next app state (incrementally). That being said, my next step is to figure out how to generate new app stat...

I followed Dan Abramov's code at https://github.com/tayiorbeii/egghead.io_redux_course_notes/blob/master/08-Reducer_Composition_with_Arrays.md I am getting error message "Unexpected token at line ...

I believe I'm copying the Todo tutorial pretty much line for line, I am getting this error: Error: Reducer "addReport" returned undefined during initialization. If the state passed to the reduc...

As a Redux beginner, given (the idea of) a somewhat larger application I imagine a root reducer similar to: const rootReducer = combineReducers({ accounting, crm, sales }) Application state in t...

In many MapReduce programs, I see a reducer being used as a combiner as well. I know this is because of the specific nature of those programs. But I am wondering if they can be different.

In many resources on Reducers (like the canonical blog post by Rich Hickey), it's claimed that reducers are faster than the regular collection functions ((map ... (filter ...)) etc.) because there ...

I wan't to add a property sections: [] to my object formOpen in the reducer, I receive my object formOpen from my server with other properties and I want to add this one, how can I do that here ? T...

I'm making a form component with React, and want to store the form(s) and field(s) state with Redux. So I have a form reducer and a formField reducer. I first followed my gut feeling and tried ne...

I enjoy the concept of reducer composition in Redux, but have run into a scenario where I would like to split a reducer up, but the children reducers would then rely on state-slices from the others...

I'm trying to work out the ideal way to update several top level fields on my state tree while still maintaining split reducers. Here's a simple solution that I've come up with. var state = { fi...

In her talk The Future Of Clojure Bodil makes the following claim: Guy Steele gave a talk at ICFP called Organizing Functional Code for Parallel Execution (or, foldl and foldr Considered Slightl...

I'm wondering why the code below provides no speedup in the case of r/fold? Am I misunderstanding something about reducers? I'm running it on a pretty slow (although with 2 cores) Ubuntu 12.04 dev...

Is there a way to test a reduce class with MRUnit that uses MultipleOutputFormat to write to multiple output files?

In the MapReduce framework, one reducer is used for each key generated by the mapper. So you would think that specifying the number of Reducers in Hadoop MapReduce wouldn't make any sense because ...

Why is mapping/reducing with reducers library has worse performance than normal map/reduce? user=> (time (reduce + (map inc (range 100000000)))) "Elapsed time: 14412.627966 msecs" 5000000050000...

(require '[clojure.core.reducers :as r]) (def data (into [] (take 10000000 (repeatedly #(rand-int 1000))))) (defn frequencies [coll] (reduce (fn [counts x] (merge-with + counts {x 1})) {} coll...

I'm trying to convert the following example to the new Clojure 1.5 reducers library: (reduce max (map inc (range 10))) ;=> 10 When I change it- I get the following error: (r/fold max (r/map...

A Combiner runs after the Mapper and before the Reducer,it will receive as input all data emitted by the Mapper instances on a given node. then emits output to the Reducers. And also,If a reduce f...

I am trying to create a mapper only job via AWS (a streaming job). The reducer field is required, so I am giving a dummy executable, and adding -jobconf mapred.map.tasks=0 to the Extra Args box. In...