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Re: how to ensure loop unrolling with template programming


Thanks for your reply!

Your provided code doesn't seem to work:

unroll.cc: In constructor repeat<I>::repeat(F):
unroll.cc:4: error: declaration of repeat<(I - 1)> f shadows a parameter
unroll.cc: In function void foo():
unroll.cc:14: error: no matching function for call to repeat<4u>::repeat()
unroll.cc:2: note: candidates are: repeat<4u>::repeat(const repeat<4u>)

Frank


On Fri, 9 Jul 2010, me22 wrote:


On 9 July 2010 02:29, Frank Winter <frank.winter@desy.de> wrote:

How can I make sure the compiler unrolls the loop and inlines all function calls? Do I have to use the preprocessor in my case?


if you're *really* sure you know so much better than the heuristics, then: - __attribute__((__force_inline__)) or something like that will inline the calls - And change the loop to one at compile time using template specialization

template <unsigned I>
struct repeat {
   template <typename F>
   repeat(F f) { f(); repeat<I-1>(f); }
};
template <>
struct repeat<0> {
   template <typename F>
   repeat(F) {}
};

void bar();
void foo() {
   repeat<4>(bar);
}

HTH,
~ Scott




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