Author: Vincent Diepeveen
Date: 10:49:00 11/04/02
Go up one level in this thread
On November 04, 2002 at 13:29:04, Robert Hyatt wrote: >On November 04, 2002 at 09:39:14, Vincent Diepeveen wrote: > >>On November 04, 2002 at 06:40:14, Pham Minh Tri wrote: >> >> >>I hardly use asserts in DIEP. If i need one i usually use a >>printf, which gets removed using a // when it is tested well >>and a year later or so removed. >> >>I guess bob has the same habit. > >Actually I have a lot of debugging code in crafty. I surround the debug >blocks with something like this: > >#if defined (DEBUG) > ... >#endif Exactly, but i don't expect you to make mistakes like next in your evaluation: if( <pattern> && quickboard[sq-5] == blackbishop ) ... Now depending upon pattern that is a possible boundsbug. However that type of bugs are very common in MOVEI type programs. Especially the ones not boundschecked. I would not expect you to make that type of bugs however. Most people therefore use loads of asserts to check for example: assert(sq-5); or in 'compatible' Nalimowintel notation: ASSERT(sq-5); >I don't _always_ use DEBUG. I have DEBUGSMP so that I can just get the >parallel search debug information without all the evaluation and search debug >info. I also have a bunch of different DEBUG macros for evaluation so that I >can just get the output from the particular piece of code I am working on. > > > >> >>I boundscheck carefully though and if i detect a difference in >>node count somewhere then i am going to check it out and do not >>ignore it or claim the compiler is to blame :) >> > > >I thought you were claiming that the Intel compiler had many such >bugs? :) > > > > >>Note that it is a hard truth that compilers *do* make errors, >>but in 99.99% of the cases it is a bug in the program, so finding >>them happens very seldom. Basically i just found out some stupid >>things in gcc and in intel c++. >> >>Best regards, >>Vincent > > >I think _the_ most common type of bug is unitialized data. That is almost >_always_ the problem when a program changes its behavior when you insert >a function call (such as printf()). And these bugs +must+ be found of course, >or the program will always have a random component in the evaluation that >will change when optimization level is changed, new functions are called, or >a new compiler/computer architecture is used... > > > > > >> >>>On November 03, 2002 at 13:47:57, Vincent Diepeveen wrote: >>> >>>>On November 03, 2002 at 12:23:50, Russell Reagan wrote: >>>> >>>>Do you have an assert for every index in your program? >>>> >>>>If not then a boundschecker might be an idea to try as well :) >>>> >>>>>What I usually do to find bugs is use the assert() macro (in assert.h, or you >>>>>could write your own). Basically what you do is you assert things you know >>>>>should be true, such as an index into an array being in bounds. If it's false, >>>>>your program will halt and let you know where the error occured. For example: >>>>> >>>>>assert(i < MAX_VALUE); >>>>>myArray[i] = SomeFunction(x); >>>>> >>>>>That way, when you run the program, it will make sure that i is within bounds. >>>>>The cool thing about this is that it only does this in debug mode. In release >>>>>mode the assert()'s go away, so there is no speed penalty. In my programs I go >>>>>crazy with asserts, and put them all over the place, and it helps find some bugs >>>>>I wouldn't have found without the asserts. Yes, it will run slower in debug >>>>>mode, but the point of debug mode is to find bugs, not to run fast. >>>>> >>>>>Russell >>> >>>I agree that use of asserts in everywhere is one of the best experiences to >>>share (including check bounds). Sometimes my new changes can trigger some dozens >>>of asserts. Without asserts, my program can run two times slower in debug mode, >>>but now, it is 20-30 times (in term of nodes per second) as slow as it in >>>release mode. The big benefit is I can fast develop program, try many new ideas >>>without worrying much about new errors. >>> >>>One of amazing thing to me is that I don't find out asserts in Crafty. So I >>>guess Bob used a special program to clean up the developing versions before >>>releasing. >>>Bob, is it correct? Thanks :)
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