Skip to content
By using Twitter’s services you agree to our Cookies Use. We and our partners operate globally and use cookies, including for analytics, personalisation, and ads.
  • Home Home Home, current page.
  • About

Saved searches

  • Remove
  • In this conversation
    Verified accountProtected Tweets @
Suggested users
  • Verified accountProtected Tweets @
  • Verified accountProtected Tweets @
  • Language: English
    • Bahasa Indonesia
    • Bahasa Melayu
    • Català
    • Čeština
    • Dansk
    • Deutsch
    • English UK
    • Español
    • Filipino
    • Français
    • Hrvatski
    • Italiano
    • Magyar
    • Nederlands
    • Norsk
    • Polski
    • Português
    • Română
    • Slovenčina
    • Suomi
    • Svenska
    • Tiếng Việt
    • Türkçe
    • Ελληνικά
    • Български език
    • Русский
    • Српски
    • Українська мова
    • עִבְרִית
    • العربية
    • فارسی
    • मराठी
    • हिन्दी
    • বাংলা
    • ગુજરાતી
    • தமிழ்
    • ಕನ್ನಡ
    • ภาษาไทย
    • 한국어
    • 日本語
    • 简体中文
    • 繁體中文
  • Have an account? Log in
    Have an account?
    · Forgot password?

    New to Twitter?
    Sign up
cmuratori's profile
Casey Muratori
Casey Muratori
Casey Muratori
@cmuratori

Tweets

Casey Muratori

@cmuratori

I'm worried that the baby thinks people can't change.

Seattle
caseymuratori.com
Joined March 2009

Tweets

  • © 2021 Twitter
  • About
  • Help Center
  • Terms
  • Privacy policy
  • Cookies
  • Ads info
Dismiss
Previous
Next

Go to a person's profile

Saved searches

  • Remove
  • In this conversation
    Verified accountProtected Tweets @
Suggested users
  • Verified accountProtected Tweets @
  • Verified accountProtected Tweets @

Promote this Tweet

Block

  • Tweet with a location

    You can add location information to your Tweets, such as your city or precise location, from the web and via third-party applications. You always have the option to delete your Tweet location history. Learn more

    Your lists

    Create a new list


    Under 100 characters, optional

    Privacy

    Copy link to Tweet

    Embed this Tweet

    Embed this Video

    Add this Tweet to your website by copying the code below. Learn more

    Add this video to your website by copying the code below. Learn more

    Hmm, there was a problem reaching the server.

    By embedding Twitter content in your website or app, you are agreeing to the Twitter Developer Agreement and Developer Policy.

    Preview

    Why you're seeing this ad

    Log in to Twitter

    · Forgot password?
    Don't have an account? Sign up »

    Sign up for Twitter

    Not on Twitter? Sign up, tune into the things you care about, and get updates as they happen.

    Sign up
    Have an account? Log in »

    Two-way (sending and receiving) short codes:

    Country Code For customers of
    United States 40404 (any)
    Canada 21212 (any)
    United Kingdom 86444 Vodafone, Orange, 3, O2
    Brazil 40404 Nextel, TIM
    Haiti 40404 Digicel, Voila
    Ireland 51210 Vodafone, O2
    India 53000 Bharti Airtel, Videocon, Reliance
    Indonesia 89887 AXIS, 3, Telkomsel, Indosat, XL Axiata
    Italy 4880804 Wind
    3424486444 Vodafone
    » See SMS short codes for other countries

    Confirmation

     

    Welcome home!

    This timeline is where you’ll spend most of your time, getting instant updates about what matters to you.

    Tweets not working for you?

    Hover over the profile pic and click the Following button to unfollow any account.

    Say a lot with a little

    When you see a Tweet you love, tap the heart — it lets the person who wrote it know you shared the love.

    Spread the word

    The fastest way to share someone else’s Tweet with your followers is with a Retweet. Tap the icon to send it instantly.

    Join the conversation

    Add your thoughts about any Tweet with a Reply. Find a topic you’re passionate about, and jump right in.

    Learn the latest

    Get instant insight into what people are talking about now.

    Get more of what you love

    Follow more accounts to get instant updates about topics you care about.

    Find what's happening

    See the latest conversations about any topic instantly.

    Never miss a Moment

    Catch up instantly on the best stories happening as they unfold.

    1. Casey Muratori‏ @cmuratori Mar 10

      @jqgregory Is there a more detailed explanation somewhere of the "pipeline stall" discussed in this passage from your book? I was asked about it, and I can't think of anything to which it could be referring. (https://imgur.com/76F458o )

      1 reply 0 retweets 9 likes
    2. Jason Gregory‏ @jqgregory Mar 10
      Replying to @cmuratori

      The idea came from this talk by Alexandrescu, I think https://www.slideshare.net/andreialexandrescu1/three-optimization-tips-for-c … (slide 16) but my example in the book is incorrect/confusing. I cite i++ in a LOOP as the example, but as I actually point out in the second paragraph the issue doesn't really apply to loop indices!😊

      1 reply 0 retweets 1 like
    3. Casey Muratori‏ @cmuratori Mar 10
      Replying to @jqgregory

      [1/2] Does Alexandrescu have an explanation somewhere? That slide set doesn't really talk about it. I am having a very hard time convincing myself that there is a practical scenario where a[++i] compiles to a pipeline stall but a[i++] does not...

      1 reply 0 retweets 0 likes
    4. Casey Muratori‏ @cmuratori Mar 10
      Replying to @cmuratori @jqgregory

      [2/2] I can believe some compilers would better handle a[0] a[1] a+=2 than a[i++] a[i++], but a[++i] vs. a[i++] I can't really think of how the compiler would reliably produce more stalls with one than the other.

      1 reply 0 retweets 0 likes
    5. Jason Gregory‏ @jqgregory Mar 10
      Replying to @cmuratori

      Preincrement introduces a data hazard, because you need to wait for ++a to be calculated before it can be used. Whereas the value of a++ can be used immediately, while the increment op makes its way thru the pipeline sans data hazard.

      1 reply 0 retweets 3 likes
    6. Jason Gregory‏ @jqgregory Mar 11
      Replying to @jqgregory @cmuratori

      Sorry, ++i vs i++ (not ++a/a++). It matters because the very next thing you do is to use i to index into a[]. No useful work can be done in between. So with preinc you have to wait for the result of the inc to pop out the other end of the pipeline before indexing into a[].

      1 reply 0 retweets 0 likes
    7. Casey Muratori‏ @cmuratori Mar 11
      Replying to @jqgregory

      Sorry to keep beating this particular horse, but, I still don't get it. What platform are we talking about? This is not true on x64, right, for several reasons, not the least of which being that memory addresses have built-in offsets which execute in the same cycle as the load.

      1 reply 0 retweets 3 likes
    8. Casey Muratori‏ @cmuratori Mar 11
      Replying to @cmuratori @jqgregory

      Separately, the add instruction is single-cycle and on at least three ports (for Intel anyways), so if the compiler does decide to preincrement the value, it's hidden by the load of the base address anyway.

      1 reply 0 retweets 1 like
      Casey Muratori‏ @cmuratori Mar 11
      Replying to @cmuratori @jqgregory

      So if somebody has an example of some actual C code someone might write in the real world, where a pre-increment actually compiles to a cycle stall that would disappear if you switch to post-increment, I would like to see it so I can see what they're talking about.

      10:41 AM - 11 Mar 2021
      • 1 Like
      • Ivan Braidi
      1 reply 0 retweets 1 like
        1. New conversation
        2. Casey Muratori‏ @cmuratori Mar 11
          Replying to @cmuratori @jqgregory

          My best guess is that this was not advice from modern processors - maybe it is based on older processors that had less IPC?

          1 reply 0 retweets 2 likes
        3. Ionuț "Yo-Noots" Cava‏ @KIonutzR Mar 11
          Replying to @cmuratori @jqgregory

          Here's the talk @incomputable gave associated with that presentation. Minute 18 is where he talks about it. So, yeah, he also stated data dependencies. This was back in 2012 btw.

          1 reply 0 retweets 1 like
        4. Show replies

      Loading seems to be taking a while.

      Twitter may be over capacity or experiencing a momentary hiccup. Try again or visit Twitter Status for more information.

        Promoted Tweet

        false

        • © 2021 Twitter
        • About
        • Help Center
        • Terms
        • Privacy policy
        • Cookies
        • Ads info