Optimizing Software in C++ [pdf]

#1

Post by signa11 » Wed, Dec 16, 2015, 5:22 AM UTC

Optimizing Software in C++ [pdf]
agner.org

Re: Optimizing Software in C++ [pdf]

#2

Post by alvern » Wed, Dec 16, 2015, 11:37 PM UTC

Thank you for sharing this.

Re: Optimizing Software in C++ [pdf]

#3

Post by vvanders » Wed, Dec 16, 2015, 11:58 PM UTC

Lots of good stuff there. Caches(including i-cache and d-cache), volatile(and how it gets mis-construed), pointer-aliasing, float to int overhead, alloca. I don't think I've seen so much good performance stuff in a single place.

Re: Optimizing Software in C++ [pdf]

#4

Post by pcwalton » Thu, Dec 17, 2015, 12:39 AM UTC

This is great overall. One nitpick:

> How compilers optimize

This didn't mention scalar replacement of aggregates [1]! This is easily one of the most important optimizations for programmers in C++ and similar languages to know about.

[1]: https://books.google.com/books?id=Pq7pHwG1_OkC&pg=PA331&lpg=... is a reasonable explanation.

Re: Optimizing Software in C++ [pdf]

#5

Post by 0xFFC » Thu, Dec 17, 2015, 12:39 AM UTC

Does this have second part ? (I saw "1" at first page in headline). I am asking because I am in love with this . Thank you so much

Re: Optimizing Software in C++ [pdf]

#6

Post by 0xFFC » Thu, Dec 17, 2015, 12:49 AM UTC

0xFFC wrote: post #5

Does this have second part ? (I saw "1" at first page in headline). I am asking because I am in love with this . Thank you so much

http://www.agner.org/optimize/

for anyone who wants complete series.

Re: Optimizing Software in C++ [pdf]

#7

Post by fitzwatermellow » Thu, Dec 17, 2015, 1:50 AM UTC

Chapter 14 is twenty-four carat gold. Would love to see optimize.com as a dedicated site with Rosetta Code-style ports of optimization recipes across languages, platforms ;)

Quick link to grab all five manuals:

http://www.agner.org/optimize/optimization_manuals.zip

Re: Optimizing Software in C++ [pdf]

#8

Post by blt » Thu, Dec 17, 2015, 2:18 AM UTC

Anyone who is interested in maximizing the output of computer hardware should read this. 100% of times I've been able to significantly speed up a piece of C++ code, I did it by using a technique from this document. Cannot recommend highly enough.

Re: Optimizing Software in C++ [pdf]

#9

Post by nly » Thu, Dec 17, 2015, 4:35 AM UTC

fitzwatermellow wrote: post #7

Chapter 14 is twenty-four carat gold. Would love to see optimize.com as a dedicated site with Rosetta Code-style ports of optimization recipes across languages, platforms ;) Quick link to grab all five manuals: http://www.agner.org/optimize/optimization_manuals.zip

> Chapter 14 is twenty-four carat gold

Maybe, but the bounds-checking optimisation [14.2] just looks dangerous. If you end up with an erroneous 'int' index of -1 then the original code will error out, whereas the new code will interpret it as 2^32 - 1. This is a perfectly valid index in an array of 2^32 values. This optimisation just isn't equivalent if INT_MAX Am I missing something?

Re: Optimizing Software in C++ [pdf]

#10

Post by [deleted] » Thu, Dec 17, 2015, 5:23 AM UTC

nly wrote: post #9

fitzwatermellow wrote: post #7

Chapter 14 is twenty-four carat gold. Would love to see optimize.com as a dedicated site with Rosetta Code-style ports of optimization recipes across languages, platforms ;) Quick link to grab all five manuals: http://www.agner.org/optimize/optimization_manuals.zip

> Chapter 14 is twenty-four carat gold Maybe, but the bounds-checking optimisation [14.2] just looks dangerous. If you end up with an erroneous 'int' index of -1 then the original code will error out, whereas the new code will interpret it as 2^32 - 1. This is a perfectly valid index in an array of 2^32 values. This optimisation just isn't equivalent if INT_MAX Am I missing something?

[deleted]