And that, as you may imagine, is very slow. It also depends on the size of the heap, as it needs to visit every active object during the marking phase, so that it could be sweeped later on. It was also missing a more efficient strategy of handling differently old and new objects in a form of generations - as we now from garabge collection in CLR or JVM.
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Another issue related to data and memory usage is data structure copying. If you are working with a larger collection, you should always think about avoiding copying and be modifying in place instead.
The same goes for string manipulations. There are a whole bunch of bang methods, which perform what they do on the method receiver - instead of returning a copy. Lets take a look at files now. If you are trying to process a large file and do a simple and straight forward File.
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You should always process files line by line - in that way, the previously proceesed lines can be deallocated from memory when no longer needed. Something like:. Lastly - watch your iterators.
You should be aware when you see usage of each or map in your code, because it means iterating over collections in one chunk. That is very convinient and can save a lot of performance problems!
If you use that in a nested loop you may have some serious performace issues. There is no need to iterate over every record in memory and do some computations on it when it could be done easily and fast via one database query, like for example PostgreSQL Group By or Max functions. Read the book Ruby Performance Optimization for more and stay tunned for other articles :.
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This allocates two Strings, "" and "mike". The first, empty String is then mutated to contain "mike".
However String mutation is quite rare, more common is something like this:. Every invocation of getmike will allocate a new copy of "mike", which is then immediately thrown away as garbage, but is required because Ruby just treats the String as a method argument which might be mutated inside Hash .
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So wasteful! Ruby introduced the freeze concept many years ago to minimize allocation.
Calling freeze on an object tells Ruby to treat it as immutable. Now Ruby knows that it can treat "mike" as a constant:. Ruby 2. This will not allocate an extra String for "mike".