2*i and i*2

[Marco Alfaro]

Why 2*i is faster than i*2 ?

[Marco Pontello]

Indeed, a 2*x is translated to a SHL (shift left), while for a x*2 a normal IMUL is used. It's a "parser" thing, IMHO.

Bye!

[Michael Mattias]

I am trying to imagine what made you investigate this phenomenon.

I am stumped, you win.

[Mel Bishop]

What difference does it make as to why? He did and was puzzled by the results.

What I would like to know is how he made the speed comparisons. Just out of idle curiosity, I tried it using TIMER and both came up with zero time. I used the number 5 for the value of I.

[Marco Pontello]

For code that turn into just a couple of Asm instructions, you need to time adequately: either repeating it lots of times, or checking the RTDSC, etc.
The SHL version turn out about 15% faster, for me (with an Intel Core Duo).

Bye!

[John Gleason]

If you have PB9/5 you can use TIX too. I got speeds about 2x faster for 2*i.

#COMPILE EXE
#DIM ALL

FUNCTION PBMAIN () AS LONG

    LOCAL i, ii, ii2 AS LONG
    LOCAL t1, t2 AS QUAD, sp AS STRING
    i = 1000000
    TIX t1
    FOR ii = 1 TO 30000000  'warm up loops
       ii2 = 2 * i
       ii2 = i * 2
    NEXT
    TIX END t1

    TIX t1
    FOR ii = 1 TO 10000000
       ii2 = 2 * i
    NEXT
    TIX END t1

    TIX t2
    FOR ii = 1 TO 10000000
       ii2 = 2 * i
    NEXT
    TIX END t2
    sp =  "Both 2 * i:" & $CRLF & STR$(t1) & $CRLF & STR$(t2) & $CRLF & "ratio:" & $CRLF & STR$(t2 / t1)

    TIX t1
    FOR ii = 1 TO 10000000
       ii2 = i * 2
    NEXT
    TIX END t1

    TIX t2
    FOR ii = 1 TO 10000000
       ii2 = 2 * i
    NEXT
    TIX END t2
    ? sp & $CRLF & $CRLF & "i * 2 followed by 2 * i:" & $CRLF & STR$(t1) & $CRLF & STR$(t2) & $CRLF & "ratio:" & $CRLF & STR$(t2 / t1)

END FUNCTION

[John Petty]

I am trying to imagine what made you investigate this phenomenon.

I am stumped, you win.

So are you switching to .net?
I thought the reason most of us used PB was speed, and then knowing how to get the best speed out of it.

[Michael Mattias]

>I thought the reason most of us used PB was speed,

I would have guessed the main reason was "ease of use," at least when first getting started.

I'm sure somewhere in PB's marketing department someone has the totals off the bingo cards you get with every new product where you check off the boxes (please check all which apply, thank you!) in the section, "what made you try this product?"


MCM

[Rodney Hicks]

'speed'
'ease of use'
'executable size'
'#BLOAT'
'No Vapourware'

These are a few of our favourite things!

[Cliff Nichols]

'speed'
'ease of use'
'executable size'
'#BLOAT'
'No Vapourware'

Shall we also add

1. Each concept, not only can a solution be found but the user is willing to share how they found it???
2. The deeper you learn, the more you find friends that attempted ideas before you , and after you that can either offer help or need help achieving what they may have long since posted
3. PB allows us to "Bridge both worlds" with not only code long forgot vs "Hey HERE is the WIZBANG" and show the reason why each work

Personally I think the team at PB has done a PHENOMENAL job at keeping the masses happy, and working on the "Wish-list" and releasing what would best suit the medium, which is why I was drawn to PB and not others given the "New Technology" because the new is REALLY built on the old...but you do not realize it till you get older

[Gösta H. Lovgren-2]

I am trying to imagine what made you investigate this phenomenon.

I am stumped, you win.

Gee, haven't you ever been curious? (not to be confused with puzzled)

=============================================
To be, or not to be: that is the question:
Whether 'tis nobler in the mind to suffer
The slings and arrows of outrageous fortune,
Or to take arms against a sea of troubles ...
William Shakespeare (1546-1616)
=============================================

[Michael Mattias]

Gee, haven't you ever been curious? (not to be confused with puzzled)

Yes, but not about any potential difference in the way 2*I is compiled versus the way I*2 is compiled.

Of course I must confess to having a longtime deep-seated and unshakeable faith in the absolute veracity of the associative law of multiplication.

MCM

[Mark Farrar]

oh god

I am trying to imagine what made you investigate this phenomenon.

I am stumped, you win.

I've resisted this for a long time, but I finally broke down ... too many grains of sand in the pile.

I know you are kind of the big Kahuna around here Michael and respect you for your technical knowledge concerning PB, but you really never give it a rest do you? Consider that not all good ideas, questions (or answers) come from you. I wonder why you feel the need to respond to so many others only to criticize or demean.

ok ... before we get into flame wars about who is qualified to say what to who ... I have 3 Engineering degrees too ... you don't see me giving out crap like candy on this site.

Now ... I brace and wait for the much expected witty repartee.

[Mel Bishop]

'speed'
'ease of use'
'executable size'
'#BLOAT'
'No Vapourware'

These are a few of our favourite things!

The single "most favorite" thing can be summed up in three word.

"Does it work"?

If it doesn't work, all other considerations are moot. Get it working first then tweek it later.

[Michael Mattias]

What surprised me was how totally out of left field this was.

It's like waking up and saying, "today I am going to look for Tupperware on my roof" .. that is, it would never occur to me to look for a performance difference between I*2 and 2*I.

I was - and remain - curious as to what inspired this effort.

[Gösta H. Lovgren-2]

I was - and remain - curious as to what inspired this effort.

There are a wide range of possibilities. All the way from +0 to -0. And I don't have any engineering degrees. {grinning needle}

=================================
"Research is what I'm doing when
I don't know what I'm doing."
Wernher Von Braun (1912-1977)
=================================

[Barry Marks]

I have to agree with Mr. Mattias here; that is an unlikely thing to have looked into. My take on his comment was that he was pleasantly surprised at this find, as was I.

It seems as though everyone is so accustomed to MM's chagrin that when it wasn't there, for a change, you imagined that it was.

Barry

[John Petty]

It's like waking up and saying, "today I am going to look for Tupperware on my roof" .

I get disapointed most days, as I always look on my roof to see if some new gift has arrived, don't you?

[Michael Mattias]

If PB had just done "multiply" when it sees "*" all this would be moot, you know.

That is, perhaps it should have been a user responsibilty to optimize multiplication and division by integral powers of two using the SHIFT statement provided.

[Barry Marks]

If PB had just done "multiply" when it sees "*" all this would be moot, you know.

That is, perhaps it should have been a user responsibilty to optimize multiplication and division by integral powers of two using the SHIFT statement provided.

Sure it's the user's responsibility if the compiler doesn't do it, but it would be nice if the compiler did.

Barry