Deadline 2025-11-03 23:59
All filenames refer to the g0.complang.tuwien.ac.at. You should perform your measurements on this machine.
Following the Setup below will give you a directory 2 in a working directory of your git project, containing Exercises2.txt and other files.
Answer the questions by editing Exercises2.txt with a text editor, inserting parts of the transcript where needed. For answers where the supporting evidence is longer, put the supporting evidence in a file (or several) in the same directory. Don’t forget to commit and push the directory and the relevant files before the deadline.
Please do not just answer the questions, but document how you arrived at the answers (this is also useful for preparing yourself for the interview part of the exam later in the semester). A good way to do that for some questions is to provide transcripts of your shell sessions. You can either cut-and-paste the text from the terminal session, or use script -f <filename> to write the transcript to the named file (and then copy parts of this transcript into your Exercises2.txt).
cd into a working directory of your git project for Efficient Programs on the course machine. Perform
unzip /nfs/a5/anton/pub/anton/lvas/efficient/25/2.zip
git add 2The directory 2 contains Exercises2.txt (fill in the answers there) and the files mentioned below and a Makefile.
make now measures 100,000,000 iterations of one the loops in each of the functions in e2work1.c.
For the modifications below, you must not change the source code of the data structures, the number of iterations, e2main1.c, or the fact that each instance of the data structures is visited once by each call to the functions in e2work1.c. Your changes may modify the payload during execution and may change the result of the computation. You should add code that is executed on each iteration. You may add setup code worth up to 20 cycles or 20 instructions in each of the functions of e2work1.c, but the lion’s share of the additional cycles or instructions should come from the additional code in the loop bodies.
Note that computations in the C code that are not used (and where the compiler can determine that) will not result in instructions in the executable code.
The goal of this exercise is that you get hands-on experience on how latency and bandwidth (in this case instruction execution bandwidth) influence performance.
Modify list1() to execute as many instructions:u as you can manage without exceeding 600,000,000 cycles:u. How many instructions:u does the result execute?
Modify array1() to perform the computations corresponding to your new list1(). How many cycles:u does your newarray1()` take?
Modify array2() to consume as many cycles:u as you can manage without exceeding 810,000,000 instructions:u. How many cycles:u does your new array2() take?
Modify list2() to perform the computations corresponding to your new array2(). How many cycles:u does your new list2() take?