Re: No templates for performance?

BGB <>
Sat, 26 May 2012 00:00:48 -0500
On 5/17/2012 2:29 PM, Jorgen Grahn wrote:

On Thu, 2012-05-17, Juha Nieminen wrote:

Pavel<> wrote:

Instead, we either instantiate code with all possible
combinations of template parameters (code bloating in its best)

Ok, I have decided to not take seriously anybody who uses the term
"code bloat" to describe templates. It's just a myth that people keep
repeating like parrots, with little actual evidence.

Yes. I'm very tempted to start trying to refute claims from Pavel and
S.L. in this thread ... but then I do a reality check. Templates
(writing new ones, and especially using the standard library's
containers and algorithms) are one of the cornerstones of modern C++.

Put differently, if I want C, I know where to find it.

FWIW, even in C, there is a "sort-of" analogue:
multi-line macros.

for example (grabbing something from some of my own code):
#define BVT_JMPCC_BODY(ty, cc) \
    ty *u, *v; \
    if(cur->data) \
    { \
        BVT_PopXY_Ty(ty, u, v); \
        if((*u)cc(*v)) \
        { \
            BVT_FreeUV_Ty(ty, u, v); \
            return((BSVM_ThreadOp *)(cur->data)); \
        } \
        BVT_FreeUV_Ty(ty, u, v); \
        return(cur->next); \
    } \
    cur->data=(void *)BSVM_Thread_GetOpJumpTarget(ctx, cur, cur->i); \
    if(cur->data) { return(cur->fcn(ctx, cur)); } \
    else { *(int *)-1=-1; } \

note that this macro in turn invokes several other macros, ...
and contains a self-destruct mechanism...

in this case it was being used fairly effectively, and the logic would
likely have been repeated either via a macro or via copy/paste anyways
(macros ended up used frequently in the region of code in question).

great fun...

(I also note that this is a re-run of a discussion back in January.
See e.g. Message-ID:<jgmUq.16032$>.
Same people involved, and I bet the same outcome: no consensus.)


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