Yeah, it's an interesting adjustment. For those of us who began coding on
things like 8-bit 64Mhz 16Mb boxes, optimizing code was absolutely essential.
Now, my desktop is a 4-core 2.8Ghz (you can get an 8 core I7 laptop for under
$700), 8Gb of RAM 64 bit machine, and it's nearly obsolete. When I code (or
review code), I'm not so much looking to wrest out every last system call
(although I still do it out of habit), I'm just looking to make sure there are
no egregious errors that will affect performance (or stability, or...), like
executing a select instead of doing an internal one. Given a minimum of
self-created bottlenecks, disk IO is still the limiting factor, (usually) not
CPU cycles, especially if your OS isn't bloatware. In a few short years, we'll
have solid state disks and a new set of problems. BTW, anyone see IBM's new
offering, Pure System? In many ways, a 180 degree turn: everything is back in
one rack: cpu's, storage, networking...
> Date: Fri, 20 Apr 2012 08:27:48 -0500
> From: [email protected]
> To: [email protected]
> Subject: Re: [U2] Case Statement with only two cases
>
> A respectful correction, Brian.
>
> On 4/20/2012 4:50 AM, Brian Leach wrote:
> > it's all the same to the compiler.
> > -----Original Message-----
> > BEGIN CASE
> > CASE A = "TEST"; GOSUB DO.SOMETHING
> > CASE 1; GOSUB DO.SOMETHING.ELSE
> > END CASE
> > versus this
> > IF A = "TEST" THEN GOSUB DO.SOMETHING ELSE GOSUB DO.SOMETHING.ELSE
> -----
>
> Since we seem to be finding every nit in the bottom of this empty
> barrel, here's one more.
> There are 2 compiler difference as shown by VLIST (UV10.2):
>
> 00001: BEGIN CASE
>
> 00002: CASE A = "TEST"; GOSUB DO.SOMETHING
> 00002 00000 : 06E eq A "TEST" => $R0
> 00002 00008 : 2DE testfw $R0 00020:
> 00002 00010 : 0A4 gosub 00060:
>
>
> 00003: CASE 1; GOSUB DO.SOMETHING.ELSE
> 00003 00018 : 0C2 jump 00038:
> 00003 00020 : 2DE testfw 1 00038: <-------------- Extra
> worthless test
> 00003 00028 : 0A4 gosub 00062:
>
> 00004: END CASE
> 00004 00030 : 0C2 jump 00038: <-------------- Extra worthless
> jump (to next line)
>
> (Source lineup is goofy. This jump is really part
>
> of source line 3. RAID is confusing, too.
> A
> discussion for a different thread.)
>
> 00005: IF A = "TEST" THEN GOSUB DO.SOMETHING ELSE GOSUB DO.SOMETHING.ELSE
> 00005 00038 : 06E eq A "TEST" => $R0
> 00005 00040 : 2DE testfw $R0 00058:
> 00005 00048 : 0A4 gosub 00060:
> 00005 00050 : 0C2 jump 00060:
> 00005 00058 : 0A4 gosub 00062:
>
> 00006: STOP
> 00006 00060 : 190 stop
>
>
> With the speed of today's machines it would be hard to find a place
> where that performance makes a difference.
>
> Rocket could theoretically clean up both (or either independently) if
> the compiler was smart enough:
>
> 1. to know that a logical test outcome was predestined at compile time
> (It already does that sort of thing in other situations.). Then it
> could compile only 1 of the 2 paths the testfw takes. (e.g. 0020x).
> Same for IF, WHILE, or UNTIL constructs.
>
> 2. To recognize the final CASE before the END CASE never needs to jump
> (e.g., 0030x).
>
> I wonder if we've already wasted more electrical & biological energy by
> me writing this email, dispersing it around the globe, and you reading
> it, than all the machine cycles wasted executing the 2 worthless tests
> in all the object scattered around the universe that Rocket could
> theoretically optimize.
>
> cds
>
>
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