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aus+uk / uk.comp.sys.mac / Re: Studio - something wrong here

SubjectAuthor
* Studio - something wrong hereRichard Tobin
+- Studio - something wrong herenospam
`- Studio - something wrong hereTheo

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Studio - something wrong here

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From: rich...@cogsci.ed.ac.uk (Richard Tobin)
Newsgroups: uk.comp.sys.mac
Subject: Studio - something wrong here
Date: Mon, 25 Apr 2022 16:30:55 +0000 (UTC)
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 by: Richard Tobin - Mon, 25 Apr 2022 16:30 UTC

My Mac Studio finally arrived, so I thought I'd run one of my programs
to see how fast it is. It's a straightforward single-threaded C
program that generates suguru puzzles.

On my old 2011 iMac, it took 93 minutes to generate all the 5x5
sugurus. The same binary, under rosetta on the New Mac Studio, took
44 minutes.

So far, so good. More than twice as fast even when emulated. But
then I compiled it natively, and it took 64 minutes! Much slower than
the emulated code, and only 30% quicker than a 2011 iMac.

What's going on?

(All the times are CPU times, and very similar to the elapsed time.)

-- Richard

Re: Studio - something wrong here

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Subject: Re: Studio - something wrong here
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 by: nospam - Mon, 25 Apr 2022 17:15 UTC

In article <t46ibv$2olc$1@macpro.inf.ed.ac.uk>, Richard Tobin
<richard@cogsci.ed.ac.uk> wrote:

> My Mac Studio finally arrived, so I thought I'd run one of my programs
> to see how fast it is. It's a straightforward single-threaded C
> program that generates suguru puzzles.
>
> On my old 2011 iMac, it took 93 minutes to generate all the 5x5
> sugurus. The same binary, under rosetta on the New Mac Studio, took
> 44 minutes.
>
> So far, so good. More than twice as fast even when emulated. But
> then I compiled it natively, and it took 64 minutes! Much slower than
> the emulated code, and only 30% quicker than a 2011 iMac.
>
> What's going on?

what does instruments say?

Re: Studio - something wrong here

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From: theom+n...@chiark.greenend.org.uk (Theo)
Newsgroups: uk.comp.sys.mac
Subject: Re: Studio - something wrong here
Date: 25 Apr 2022 20:42:15 +0100 (BST)
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 by: Theo - Mon, 25 Apr 2022 19:42 UTC

Richard Tobin <richard@cogsci.ed.ac.uk> wrote:
> My Mac Studio finally arrived, so I thought I'd run one of my programs
> to see how fast it is. It's a straightforward single-threaded C
> program that generates suguru puzzles.
>
> On my old 2011 iMac, it took 93 minutes to generate all the 5x5
> sugurus. The same binary, under rosetta on the New Mac Studio, took
> 44 minutes.
>
> So far, so good. More than twice as fast even when emulated. But
> then I compiled it natively, and it took 64 minutes! Much slower than
> the emulated code, and only 30% quicker than a 2011 iMac.
>
> What's going on?

Some bytecode interpreters can be fast because they fit in the instruction
cache, which means their instructions don't have to be fetched from memory.
It's possible Rosetta fits. Then the difference is between the density and
expressiveness of x86 and aarch64 instructions which sets the amount of
compute you can get done in a memory transaction (from DRAM or cache). If
you had a lot of one-byte x86 instructions, or big vector operations, it's
possible you'd get more done for given memory traffic compared with the
aarch64 instructions.

Xcode has the 'Instruments' feature which records data from the hardware
Performance Monitoring Counters (PMCs) which might be able to tell you
numbers like L1 cache misses. I don't know if Rosetta has any statistics,
but it should be able to tell you what the hardware is doing.

https://en.wikipedia.org/wiki/Instruments_(software)

Theo

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