/prog/ - Why profile code?

Name: Anonymous 2009-10-03 9:04

What's the point of profilers? If I have written the code, I know which points are slow, and which do not matter.

Name: Anonymous 2009-10-03 9:19

Actually, you don't know where the points are slow. Profilers exist so you can profile where and how long your programs operate.

Name: Anonymous 2009-10-03 9:37

>>2
Actually, you don't know where the points are slow.
Is that what people really think?

Name: Anonymous 2009-10-03 9:45

>>3
Unless you've got an intimate knowledge of what your compiler is doing, you're not going to have a excellent idea of how slow/quickly your program works without a profiler. The best you can do is an educated guess.

Name: Anonymous 2009-10-03 10:00

This is how easy it is to troll prog now?

Name: Anonymous 2009-10-03 10:04

>>4

i = 0;

for (i = 0; i < 100; ++i) {

    j = i + 10;

}

print j;

Using this as an example (well, with some higher numbers, and assuming print takes 0 time), I can see that the loop part is the slowest part of the code. I furthermore know that loops are bad, so I devise a way to calculate j without looping. Perhaps I can even replace the loop by a constant value.

Name: Anonymous 2009-10-03 10:41

>>6
Now try estimating the performance of a complete computer program. Let's take Supertux as an example.

Name: Anonymous 2009-10-03 10:54

>>7
I did not write that program, and that program uses a lot of external libraries which makes it impossible to tell how much a library call costs. In such a case a profiler might be useful, but that is a very rare exception.

Name: Anonymous 2009-10-03 12:12

>>6
~ $ cat crap.c #include <stdio.h> int main() { int j = 0; for(int i = 0; i < 100; ++i) j = i + 10; printf("%d\n", j); } ~ $ gcc -std=c99 -O3 -Wall -Wextra -pedantic crap.c -S -masm=intel ~ $ cat crap.s .file "crap.c" .intel_syntax noprefix .section .rodata.str1.1,"aMS",@progbits,1 .LC0: .string "%d\n" .text .p2align 4,,15 .globl main .type main, @function main: push ebp mov ebp, esp and esp, -16 sub esp, 16 mov DWORD PTR [esp+4], 109 mov DWORD PTR [esp], OFFSET FLAT:.LC0 call printf xor eax, eax leave ret .size main, .-main .ident "GCC: (GNU) 4.4.1" .section .note.GNU-stack,"",@progbits

Replace 109 with 5950 if you meant j += ...
IHBT

Name: Anonymous 2009-10-03 12:28

>>5
Welcome to 2009, where have you been for all these years?

Name: Anonymous 2009-10-03 14:07

Yeah, this one was terrible.

Name: Anonymous 2009-10-03 17:25

>>8
Working on others' code is an exception.
Using libraries is rare.
This is what toy language programmers really believe.

Name: Anonymous 2009-10-03 18:04

>>12
Well, if you are using libraries you can't very well optimize them, now can you?

Real men reinvent the wheel at least once a day.

Name: Anonymous 2009-10-03 18:28

profile my anus

Why profile code?

1 Name: Anonymous 2009-10-03 9:04

2 Name: Anonymous 2009-10-03 9:19

3 Name: Anonymous 2009-10-03 9:37

4 Name: Anonymous 2009-10-03 9:45

5 Name: Anonymous 2009-10-03 10:00

6 Name: Anonymous 2009-10-03 10:04

7 Name: Anonymous 2009-10-03 10:41

8 Name: Anonymous 2009-10-03 10:54

9 Name: Anonymous 2009-10-03 12:12

10 Name: Anonymous 2009-10-03 12:28

11 Name: Anonymous 2009-10-03 14:07

12 Name: Anonymous 2009-10-03 17:25

13 Name: Anonymous 2009-10-03 18:04

14 Name: Anonymous 2009-10-03 18:28

18 Name: Anonymous 2011-02-03 6:09