Skip to main content

Lab2

Complied C Lab

In this lab, we were asked to compile a C program, using gcc command with different options.

At the beginning of this lab, we wrote a simple C program that prints a message:

Then using gcc command and the following compiler options to compile the program:
-g               # enable debugging information
-O0              # do not optimize (that's a capital letter and then the digit zero)
-fno-builtin     # do not use builtin function optimizations

Note that the size of file is 73088 bytes

We can use objdump --source a.out command to show source code, the source code is under <main> section. And readelf -p .rodata a.out contains the string to be printed.


Then we add the option "-static" to recompile the program, found out the size is changed to 696264 bytes, which is bigger than the original program. And section headers are also increased.

Next, I removed the builtin function optimization by remove option "-fno-builtin", and rebuilt the program. Note that the size is smaller than using the built-in function to 696256 bytes.

Then I disabled debugging information by removing option "-g"
Note that the size is smaller to 693840 bytes
And there are also more section headers and disassembly outputs.

With adding a number to the argument of printf() function, we note the argument is assigned to a register and added to a stack, and moved.

Finally, I added an option "-O3" instead of "-O0", which is stand to optimization level to 3, I found that the size is not changed, but the lines are less than original.

Comments

Post a Comment

Popular posts from this blog

Lab 3

In this lab, we are going to use Assembly language to finish 3 parts. 1. As we are getting familiar with Assembly language, we will create a loop in Assembly to prints out 10 times of "Hello World!". This part is quite easy to do it, here is the source code for x86_64 assembler: ------------------------------------------------------ .text .globl    _start start = 0                       /* starting value for the loop index; note that this is a symbol (constant), not a variable */ max = 10                        /* loop exits when the index hits this number (loop condition is i<max) */ _start:     mov     $start,%r15         /* loop index */     mov     %r15,%r10 loop:         /* ... body of the loop ... do something useful here ... */   ...
Post a Comment
Read more

SPO600 - Project - Stage One

In our final project, the project will split into 3 stages. This is the first stage of my SPO600 course project. In this stage, we are given a task to find an open source software package that includes a CPU-intensive function or method that compiles to machine code. After I chose the open source software package, I will have to benchmark the performance of the software function on an AArach64 system. When the benchmark job is completed, I will have to think about my strategy that attempts to optimize the hash function for better performance on an AArch64 system and identify it, because those strategies will be used in the second stage of the project. With so many software, I would say picking software is the hardest job in the project, which is the major reason it took me so long to get this post going. But after a lot of research, I picked a software called SSDUP , it is a traffic-aware SSD burst buffer for HPC systems. You can find the source code over here: https://github.com/CGC...
Post a Comment
Read more

Lab 5

In this lab, we are going to use different approaches to scale volume of sound, and the algorithm’s effect on system performance. Here is some basic knowledge of digital sound: Digital sound is usually represented by a signed 16-bit integer signal sample, taken at a rate of around 44.1 or 48 thousand samples per second for one stream of samples for the left and right stereo channels. In order to change the volume of sound, we will have to scale the volume factor for each sample, the range of 0.00 to 1.00 (silence to full volume). Here is the source code I got from professor: (vol1.h) ------------------------------------------------- #include <stdlib.h> #include <stdio.h> #include <stdint.h> #include "vol.h" // Function to scale a sound sample using a volume_factor // in the range of 0.00 to 1.00. static inline int16_t scale_sample(int16_t sample, float volume_factor) { return (int16_t) (volume_factor * (float) sample); } int main() { // Al...
Post a Comment
Read more