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    <p>You get an <code>OutOfMemoryException</code> because inside the loop you allocate a string and store it in an <code>ArrayList</code>. The strings have to stay in memory until the <code>ArrayList</code> is garbage collected and your loop creates more strings than you will be able to store.</p> <p>If you simply want to check the string for a condition you should put the check inside the loop:</p> <pre><code>for ( ... some crazy loop ...) { var word = ... create word ... if (!WordPassesTest(word)) { Console.WriteLine(word + " failed test."); return false; } } return true; </code></pre> <p>Then you only need storage for a single word. Of course, if the loop is crazy enough, it will not terminate before the end of the universe as we know it.</p> <p>If you need to execute many nested but similar loops you can use recursion to simplify the code. Here is an example that is not incredible efficient, but at least it is simple:</p> <pre><code>Char[] chars = "ABCD".ToCharArray(); IEnumerable&lt;String&gt; GenerateStrings(Int32 length) { if (length == 0) { yield return String.Empty; yield break; } var strings = chars.SelectMany(c =&gt; GenerateStrings(length - 1), (c, s) =&gt; c + s); foreach (var str in strings) yield return str; } </code></pre> <p>Calling <code>GenerateStrings(3)</code> will generate all strings of length 3 using lazy evaluation (so no additional storage is required for the strings).</p> <p>Building on top of an <code>IEnumerable</code> generating your strings you can create primites to buffer and process buffers of strings. An easy solution is to using Reactive Extensions for .NET. Here you already have a <code>Buffer</code> primitive:</p> <pre><code> GenerateStrings(3) .ToObservable() .Buffer(10) .Subscribe(list =&gt; ... ship the list to another computer and process it ...); </code></pre> <p>The lambda in <code>Subscribe</code> will be called with a <code>List&lt;String&gt;</code> with at most 10 strings (the parameter provided in the call to <code>Buffer</code>).</p> <p>Unless you have an infinte number of computers you will still have to pull the computers from a pool and only recycle them back to the pool when they have finished the computation.</p> <p>It should be obvious from the comments on this question that you will not be able to process 26^30 strings even if you have multiple computers at your disposal.</p>
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    1. POC# Char permutation with repetition on large set of chars
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    1. COThis was my plan to do,but If Im going to execute it on multiple pc I have to set some limit to each PC and to each thread of Application.Example: 1.PC - 1 Thread compares 0-2000000 Save number 2000000 to var 2.PC - 2 Thread compares 2000000-4000000 Save number to same var So when new thread starts it can know that first 4000000 Lines are being checked and that it should start from 4000000 record. After Threads are full Save progress to file on network or SQL Db so another pc can take next records and so on.
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    2. COGreat example thank you! One more question should I use Take to put strings in array then compare or shouldi change your method slightly and ad if condition so it only return correct match. Do you have any solution to my first comment for threading?
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    3. CO@user1010609: Use recursion if you don't want to write nested loops. Use `IEnumerable` to use lazy evaluation. Use primitives like `Buffer` to chop your workload into manageable parts.
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