Does anybody really use a Profiler?

[BillWoodruff]

Your point is much clearer, and more powerfully expressed ... to me ... with this excellently written personal example. thanks, Bill

“I have diligently numbered the days of pure and genuine happiness which have fallen to my lot: They amount to 14.” Abd-Ar Rahman III, Caliph of Cordoba, circa 950CE.

[Kornfeld Eliyahu Peter]

SledgeHammer01 wrote:

look at a block of code for a few minutes and instantly identify why it's slow

I hate to destroy your self confidence, but some code is work just perfectly with input A and perform terribly with input B (see compression algorithms), so looking at the code and even understanding it means nothing without the real-time environment...

SledgeHammer01 wrote:

maybe it's just a talent

The word you looking for is neglection me think...

SledgeHammer01 wrote:

from my limited experience with profilers

Better learn profilesr (how to use and interpret its output) and after that we will hear you again...

I'm not questioning your powers of observation; I'm merely remarking upon the paradox of asking a masked man who he is. (V)

[SledgeHammer01]

Kornfeld Eliyahu Peter wrote:

I hate to destroy your self confidence, but some code is work just perfectly with input A and perform terribly with input B (see compression algorithms), so looking at the code and even understanding it means nothing without the real-time environment...

I think you are very confused. I never said I can compile or disassemble code in my head. Nor did I ever say I can optimize code for every single condition that will ever come up. OF COURSE you need the input that causes the issue LOL. You couldn't use your profiler without the proper input either :confused: :confused: :confused:. Given the problem input, yes, I can solve the issue. Duh. That was the whole point of the discussion. EDIT: Actually, I take that back. If the code is in a highly specialized area like math or science where you need a PHD in the specialized area to understand the algorithm, that's a different story. In that case, a profiler wouldn't help you either. So your point is moot. Let's say you are an expert on compression and have a few PHDs in math. I'll give you all the time in the world and any and all profilers you could ever want. I'm willing to bet you $$$ that you would be unable to resolve a performance issue in a DIFFERENT highly specialized area like say nuclear physics.

[Kornfeld Eliyahu Peter]

SledgeHammer01 wrote:

You couldn't use your profiler without the proper input either

That's profiler IS. Check your code in real-time environment. And if you believe that you can solve the issue by seeing the input, you never saw real input and never understood the issue!

I'm not questioning your powers of observation; I'm merely remarking upon the paradox of asking a masked man who he is. (V)

[Nagy Vilmos]

Many, many times. Both static and dynamic profiling is an important tool in enterprise development. Yes, your basic steps are useful in a single application, but when you move into a large distributed, multi user system simple code viewing doesn't cut the mustard any more. The time it takes to look through hundreds of methods and calculate which ones will be a problem under which conditions is waisted if you have a decent set of diagnostic tools at your hand. Real example. I had a junior put together a piece of work. Simple service for validating the entry from a form. Now applying your logic above the code would check out fine. Performance was good on the test system and there were no obvious conflicts, data was being cached, look ups avoided, etc, etc, etc. The memory footprint was a pig, absolutely horrendous. And for each user the problem increased. We needed to pool resources, reduce cached data and in some places slowed down response times.

[Lost User]

I also find this curious. "You didn't use a profile, did you" is a pretty common piece of bullshit that people sling. It's almost always perfectly obviously what the problem is, or that something will be a problem, without even running the code let along profiling it. Basically what that comes down to is, if you do something stupid, it's going to suck. And preemptively not doing stupid shit is not "premature optimization". Of course it's not always obvious. For example,

xor ecx, ecx
_benchloop:
lzcnt eax, edx
add ecx, 1
jnz _benchloop

Why does this measure the latency of lzcnt, instead of its throughput? It doesn't look like it should do that, so in the original code that contained the "problem lzcnt", that problem gave me quite the chase. Initially I didn't even notice something was wrong. No actual profiler was involved though.

[Mark_Wallace]

They always just say "male, aged 18-35, who used to kick cats", so it's a waste of time even consulting them.

I wanna be a eunuchs developer! Pass me a bread knife!

[Lost User]

Much worse is when two or more threads keep each other waiting, but the synchronization is needed. For example a thread that reads input from devices and inserts the data as messages into a queue for the UI. Obviously, the UI threads frequently are going to check the queue for new messages and this access must be synchronized. If the threads lock each other out too frequently, you will have to come up with something more clever than a simple queue to eliminate the need for synchronization.

The language is JavaScript. that of Mordor, which I will not utter here
I hold an A-7 computer expert classification, Commodore. I'm well acquainted with Dr. Daystrom's theories and discoveries. The basic design of all our ship's computers are JavaScript.

[wout de zeeuw]

Good luck finding the most important bottle necks in applications of several millions lines of code without a profiler! :laugh: Hell, even in smaller applications I wouldn't even bother finding bottlenecks without a profiler. Why would you deny yourself a helpful tool?

Wout

[Nelek]

wout de zeeuw wrote:

Why would you deny yourself a helpful tool?

Because he thinks the tool sucks

M.D.V. ;) If something has a solution... Why do we have to worry about?. If it has no solution... For what reason do we have to worry about? Help me to understand what I'm saying, and I'll explain it better to you Rating helpful answers is nice, but saying thanks can be even nicer.

[Gary R Wheeler]

They do[^]. (sorry; it was just too easy)

Software Zen: delete this;

[Pete OHanlon]

I find the idea of not being able to use every tool available to you is incredibly naive. Granted that you should be able to solve simple performance problems just by looking at them, but some problems are just too big and interwoven to solve like this. Also, it's not always just your code that you're profiling - don't forget that you can often identify problem areas in code that you're using that there might be alternatives to. So yes, I use profilers regularly. I use them because I'm aware enough to know I don't know everything and that there's always something new that I can learn.

[macu]

>>> Personally, I think anybody who has been programming a while should be able to look at a block of code for a few minutes and instantly identify why it's slow. Are you serious!? Maybe for a single method or simple application, but for a complex application there's no way you can "just see it". Here's a simple real world example, recently I used a profiler to see where the bottleneck was in a web service which sits on top of 3 or 4 other layers (and I won't elaborate cause I'm keeping this simple). It turns out the bottleneck was in a piece of Microsoft code used within the ORM we use, so that was refactored to use a different method to do the same thing. No way you would have just seen that by looking, not least cause the code wasn't there to see. I'd happily admit I also wouldn't be able to just see an issue in my own code some of the time. In the above example we're talking 1000s of lines spread over multiple assemblies, why would I bother trawling through all that when I can just use a profiler? I was lucky enough to be able to test this for a single thread, good luck if you come across an issue that only occurs when you've got multiple threads involved.... :) The profiler is your friend. PS. does this mean you never use SHOWPLAN/EXPLAIN either?

[dazfuller]

Absolutely I use a profiler. You're right that looking at code can often provide the answer, but when you're code base is several thousand lines of code split across multiple components using a profiler can at the very least help identify where the problem is. It's also useful to spot things which might not be a problem with your code. Maybe a library you're using is doing something stupid, perhaps it's a little known feature of the .NET framework which is causing you problems. We recently had an issue with an older piece of software which was running into that, looking at the code would not have helped in the slightest but a profiler quickly sorted out where the problem was. A profiler should be a part of any developers toolbox, fair enough that it shouldn't be the only solution to every problem, but it should be a tool that you are comfortable using and comfortable to know when to use.

Eagles may soar, but weasels don't get sucked into jet engines

[ScottM1]

Inline SQL works fine so long as your queries are parameterised.

[Christophe Van Olmen]

Any reason why parametrized SQL code would be slower than a stored procedure? I mean, unless your statement is so big that the network overhead of sending it would be significant, a parametrized statement would have its execution plan cached by the server, same as the stored procedure. Of course it's a lot more interesting to get all the results you need in one statement instead of looping over every row and issuing a SQL statement for every row. Same goes for LDAP.

[nategoose]

I rarely use profilers, but there are a few cases when even good programmers may have trouble seeing where code is slow. Sometimes there may be a library call which you think will be fast, but turns out to be slow. This could be due to system call(s) that take longer than the programmer realizes or due to the library function's algorithm working very differently than the programmer realized. We all make assumptions about things that sometimes aren't true. One very big issue is using something like using strlen(some_string) as a constant in a C program. Many programmers use that as though it is a constant in the compiler's mind, when it may not be (GCC has an __attribute__ that lets the compiler see that it is, but it's not standard). That's the kind of thing that could end up in a loop, possibly as part of the loop check, without many programmers realizing that it's a problem. While you might see that code, there are similar circumstances which are less obvious. These are often the results of invisible code introduced by compilers for languages higher than C. Overloaded operators, copy constructors, and destructors can all have much more impact on code than programmers realize. Knowing what kinds of things your language may hide is a good way to avoid these, but some things still slip through. Other things that are easy to miss is how contentious locks, semaphores, mutexes, and other blocking operations are. These are difficult to figure out sometimes. There are also times when you need to demonstrate to someone else where the bottle necks in code are. If your cocky junior programmer weren't your subordinate but rather your boss then the output of a profiler would be something that you could use to combat the cockiness. This is particularly useful when you get "Your code is slow! Fix it!" and you can come back with "This external code/hardware/whatever, which isn't under my control, is what is slow." Another time when using a profiler would be very useful would be if there were disagreement or uncertainty over which of multiple parts of a program were responsible for the different amounts of the slowness. Maybe you need to prioritize the order in which these are addressed. For you or I it may be obvious that a section of code is slower than it has to be, but when comparing two suboptimal sections of code it is very often that eyeballs alone are not enough. There are also times when a profiler can be used to find bugs that would take a lot of stepping in a debugger to locate.

[Member 10462598]

Yes, but before I do, your original email opens up a bigger issue, I think. To demonstrate, let me ask: Does anybody really use a debugger? You see, I think that any real software engineer should be able to write bug-free code and if looking at someone else's code, should be able to identify the bugs in a fairly straight forward process. Pretty silly, right? Of course this is tonge-in-cheek, but the point is that a profiler is a tool that has a place in the engineer's toolbox. By asking the question in a way that belittles the use of the tool, it seems the results of the answers will be biased, or at least the interpretation of the results will be. (Full disclosure: Maybe there are a few who are so good they can optimize their code without a profiler, but I have learned the hard way that I am not one of those - I also used to believe profilers are for the weak.) Engineers use tools. Engineers use data from experiments to test their products and, maybe, improve them. Ignoring a tool doesn't make sense to me. I agree that profilers can be hard to use and produce a lot of noise, but using a lathe is hard, too, until you understand how to get good results from it. A profiler is not the primary tool, to be sure, but there are cases where it can be Indispensable (and has been to me). Here are where I think it makes a lot of sense: 1) Education: How does one get experienced in performance analysis and tuning with C#. And how to we know we are right? Sure, moving the invarient out of the loop make it run faster, but are there other things we could/should have done, as well? Profilers are a great way to learn where the bottlenecks are, especially when working with a new language or in a new environment. One line of code taking 85% of my runtime? How do I know it's that one? (Linq is an easy target, but what about your enum example? How do you know the first time?) I've had experiences similar to yours where I see something obviously bad and let the designer know only to be told "no way it's my problem"; When I show them profiling output proving they are the problem, they start to listen. Data are powerful things! 2) Real-time systems: I think much of the discussion on this thread has been about business-logic type applications. Large databases, searching, etc. But what if you are building a real-time processing system with streaming data in one thread, real-time analysis/processing in another and real-time display in a third (and it's actually much more complicated that that in real life as those t

[David Mott]

Always profile. ALWAYS.

string ret = string.Empty;
for (int i=0; (i < someLargeInt); i++) {
ret += AMethodThatReturnsAString (i);
}
return ret;

Compilers are smarter than you. This can be compiled into highly optimized code with loop unrolling and expression templates among other optimizations. The rule of thumb is: 1) write simple, clear, expressive code. 2) profile 3) fix hotspots

[patbob]

I've done both, and yes, using your noggin to choose a better algorithm wins over using a profiler every time. The profiler can only tell you how to make your bubble sort run faster, it can't tell you to choose to implement a quicksort instead.

We can program with only 1's, but if all you've got are zeros, you've got nothing.