In article <[email protected]> Skip wrote:
> As a newbie, I got curious about the relative speed of these strategies:
>
> 1. L R15, COUNTER
> 2. A R15,=F(+1)
> 3. ST R15, COUNTER
>
> 1. L R15, COUNTER
> 2. LA R15,1(,R15)
> 3. ST R15, COUNTER
>
> I asked my manager, who encouraged me to delve into the manual Shmuel cites.
> I decided that LA was faster because there was no storage access. The
> program ran like a banshee. It ran so fast that it was used to benchmark new
> hardware. Really!
>
> It wasn't till later that I pondered a basic flaw. As written, the program
> could not handle a counter greater than 16M because it ran in 24 bit mode.
> This was before XA. At the time I wrote it, the data base was comfortably
> within that limit, but over time, long after I had moved on, I (still)
> wonder if the application survived and if any counter ever hit the limit.
> Moral: whether or not size matters, speed is certainly not a simple metric.
L R15,COUNTER
BCTR R15,0
ST R15,COUNTER
gives a 2^31 limit, 2^32 if some care is taken when printing the totals, at
speed comparable to LA.
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