[vsipl++] [rfc] preview patch for RBO

[Stefan Seefeld]

Jules Bergmann wrote:
> This preview patch adds support for "return block optimization", for
> example to allow by-value FFTs to be lazily evaluated.

Jules,

this patch looks great !


> diff -rN -uN old-rbo-merge/src/vsip/core/fft.hpp new-rbo-merge/src/vsip/core/fft.hpp
> --- old-rbo-merge/src/vsip/core/fft.hpp	2007-02-01 10:03:50.000000000 -0500
> +++ new-rbo-merge/src/vsip/core/fft.hpp	2007-02-01 10:03:54.000000000 -0500
> @@ -25,6 +25,7 @@
>  #  include <vsip/opt/fft/workspace.hpp>
>  #endif
>  #include <vsip/core/metaprogramming.hpp>
> +#include <vsip/opt/expr/return_block.hpp>
>  #include <vsip/core/profile.hpp>
>  
>  #ifndef VSIP_IMPL_REF_IMPL
> @@ -193,16 +194,21 @@
>    {}
>  
>    template <typename ViewT>
> -  typename fft::result<O, typename ViewT::block_type>::view_type
> +  typename fft::Result_rbo<D, I, O, ViewT, workspace, axis, exponent>
> +                          ::view_type
>    operator()(ViewT in) VSIP_THROW((std::bad_alloc))
>    {
>      typename base::Scope scope(*this);
>      assert(extent(in) == extent(this->input_size()));
> -    typedef fft::result<O, typename ViewT::block_type> traits;
> -    typename traits::view_type out(traits::create(this->output_size(),
> -						  in.block().map()));
> -    workspace_.by_reference(this->backend_.get(), in, out);
> -    return out;
> +    typedef fft::Result_rbo<D, I, O, ViewT, workspace, axis, exponent>
> +      traits;
> +    typedef typename traits::functor_type functor_type;
> +    typedef typename traits::block_type   block_type;
> +    typedef typename traits::view_type    view_type;
> +
> +    functor_type rf(in, *(this->backend_.get()), workspace_);
> +    block_type block(rf);
> +    return view_type(block);
>    }
>  private:
>    std::auto_ptr<fft::backend<D, I, O, axis, exponent> > backend_;

I think it would be good to also expose the return type in a way that
allows expressions to be written out over multiple lines (as we discussed
in Palm Springs), such as

typedef Fft<...> fwd_fft_type;
typedef fwd_fft_type::result_type<my_view_type>::type fft_result_type;

...
fwd_fft_type fwd_fft(1024, 1.);
fft_result_type result(fwd_fft(my_view));
view_type C = result * kernel;
...


> diff -rN -uN old-rbo-merge/src/vsip/core/impl_tags.hpp new-rbo-merge/src/vsip/core/impl_tags.hpp
> --- old-rbo-merge/src/vsip/core/impl_tags.hpp	2007-02-01 10:03:50.000000000 -0500
> +++ new-rbo-merge/src/vsip/core/impl_tags.hpp	2007-02-01 10:03:54.000000000 -0500
> @@ -40,6 +40,7 @@
>  struct Copy_tag {};		// Optimized Copy
>  struct Op_expr_tag {};		// Special expr handling (vmmul, etc)
>  struct Simd_loop_fusion_tag {};	// SIMD Loop Fusion.
> +struct Special_tag;             // Special evaluators.
>  struct Loop_fusion_tag {};	// Generic Loop Fusion (base case).
>  struct Cbe_sdk_tag {};          // IBM CBE SDK.

Could we find a somewhat more descriptive tag name ? :-)


Thanks,
		Stefan

-- 
Stefan Seefeld
CodeSourcery
stefan at codesourcery.com
(650) 331-3385 x718