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    <p>A while back I explored this problem in my blog. Or, rather, I explored a related problem: how do you find the depth of a binary tree without using recursion? A recursive tree depth solution is trivial, but blows the stack if the tree is highly imbalanced.</p> <p>My recommendation is to study ways of solving this simpler problem, and then decide which of them, if any, could be adapted to your slightly more complex algorithm.</p> <p>Note that in these articles the examples are given entirely in JScript. However, it should not be difficult to adapt them to C#.</p> <p>Here we start by defining the problem.</p> <p><a href="http://blogs.msdn.com/ericlippert/archive/2005/07/27/recursion-part-one-recursive-data-structures-and-functions.aspx" rel="noreferrer">http://blogs.msdn.com/ericlippert/archive/2005/07/27/recursion-part-one-recursive-data-structures-and-functions.aspx</a></p> <p>The first attempt at a solution is the classic technique that you'll probably adopt: define an explicit stack; use it rather than relying upon the operating system and compiler implementing the stack for you. This is what most people do when faced with this problem.</p> <p><a href="http://blogs.msdn.com/ericlippert/archive/2005/08/01/recursion-part-two-unrolling-a-recursive-function-with-an-explicit-stack.aspx" rel="noreferrer">http://blogs.msdn.com/ericlippert/archive/2005/08/01/recursion-part-two-unrolling-a-recursive-function-with-an-explicit-stack.aspx</a></p> <p>The problem with that solution is that it's a bit of a mess. We can go even farther than simply making our own stack. We can make our own little domain-specific virtual machine that has its own heap-allocated stack, and then solve the problem by writing a program that targets that machine! This is actually easier than it sounds; the operations of the machine can be extremely high level.</p> <p><a href="http://blogs.msdn.com/ericlippert/archive/2005/08/04/recursion-part-three-building-a-dispatch-engine.aspx" rel="noreferrer">http://blogs.msdn.com/ericlippert/archive/2005/08/04/recursion-part-three-building-a-dispatch-engine.aspx</a></p> <p>And finally, if you are really a glutton for punishment (or a compiler developer) you can rewrite your program in Continuation Passing Style, thereby eliminating the need for a stack at all:</p> <p><a href="http://blogs.msdn.com/ericlippert/archive/2005/08/08/recursion-part-four-continuation-passing-style.aspx" rel="noreferrer">http://blogs.msdn.com/ericlippert/archive/2005/08/08/recursion-part-four-continuation-passing-style.aspx</a></p> <p><a href="http://blogs.msdn.com/ericlippert/archive/2005/08/11/recursion-part-five-more-on-cps.aspx" rel="noreferrer">http://blogs.msdn.com/ericlippert/archive/2005/08/11/recursion-part-five-more-on-cps.aspx</a></p> <p><a href="http://blogs.msdn.com/ericlippert/archive/2005/08/15/recursion-part-six-making-cps-work.aspx" rel="noreferrer">http://blogs.msdn.com/ericlippert/archive/2005/08/15/recursion-part-six-making-cps-work.aspx</a></p> <p>CPS is a particularly clever way of moving the implicit stack data structure off the system stack and onto the heap by encoding it in the relationships between a bunch of delegates.</p> <p>Here are all of my articles on recursion:</p> <p><a href="http://blogs.msdn.com/ericlippert/archive/tags/Recursion/default.aspx" rel="noreferrer">http://blogs.msdn.com/ericlippert/archive/tags/Recursion/default.aspx</a></p>
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    1. POHow do I avoid changing the Stack Size AND avoid getting a Stack Overflow in C#
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    1. COOr ... you could make sure your algorithm can be converted into tail recursive form by the CLR.
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    2. COC# does not ever generate the tailcall instruction. Certain versions of the jitter will notice that a particular method can be optimized using tail recursion even if the tailcall instruction is not used. However, most jitters that we've released do not have this optimization, and you should not rely upon it.
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    3. COAnd besides, your advice is not actually actionable. *How* exactly is the original poster supposed to "make sure the algorithm can be converted into a tail recursive form"? This is a complex process that requires deep understanding of implementation details of the runtime, understanding that I don't expect anyone other than the guys in building 42 to possess.
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