Floating point exception when doing UCI go command

[tissatussa]

$ ./kingfish_1.2.0_compiled_HP 
uci
id name Kingfish 1.2.0
id author Colin D
uciok
ucinewgame
go infinite
info string remaining time: 0 time allocated: 0
info depth 1 score cp 0 nodes 2 nps 2000 hashfull 0 time 1 pv d2d4 
info depth 1 score cp 46 nodes 3 nps 3000 hashfull 0 time 1 pv d2d4 
info depth 1 score cp 22 nodes 637 nps 4649 hashfull 0 time 137 pv d2d4 
info depth 1 score cp 15 nodes 1393 nps 5484 hashfull 1 time 254 pv f2f4 
info depth 2 score cp 0 nodes 1395 nps 5492 hashfull 1 time 254 pv d2d4 
info depth 2 score cp 118 nodes 1436 nps 5565 hashfull 1 time 258 pv d2d4 
info depth 2 score cp 19 nodes 1572 nps 5695 hashfull 1 time 276 pv d2d4 
info depth 2 score cp 9 nodes 2344 nps 5904 hashfull 2 time 397 pv d2d4 
info depth 3 score cp 1 nodes 2397 nps 5947 hashfull 2 time 403 pv d2d4 
info depth 3 score cp 118 nodes 2440 nps 5995 hashfull 2 time 407 pv d2d4 
info depth 3 score cp 46 nodes 2471 nps 6041 hashfull 2 time 409 pv d2d4 
[...]

$ ./kingfish_1.2.0_compiled_HP 
uci
id name Kingfish 1.2.0
id author Colin D
uciok
ucinewgame
go wtime 603000 btime 603000 winc 3000 binc 3000
info string remaining time: 753000 time allocated: 11295
Floating point exception (core dumped)

it seems my second go command is not recognized .. this gives an error in CuteChess, which uses the wtime & btime format.

[ i'm on Xubuntu 22.04 ]

[colding10]

On my machine, it works [Apple Silicon M2]. I'll have to look into this.

Could you try using a debugger like lldb or gdb, and providing the output of that?

[tissatussa]

$ gdb ./kingfish_1.2.0_compiled_HP 
GNU gdb (Ubuntu 12.1-0ubuntu1~22.04) 12.1
Copyright (C) 2022 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Type "show copying" and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<https://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
    <http://www.gnu.org/software/gdb/documentation/>.

For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from ./kingfish_1.2.0_compiled_HP...
(No debugging symbols found in ./kingfish_1.2.0_compiled_HP)
(gdb) run
Starting program: /home/roelof/Compiled/Kingfish/kingfish_1.2.0_compiled_HP 
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
uci
id name Kingfish 1.2.0
id author Colin D
uciok
ucinewgame
go wtime 603000 btime 603000 winc 3000 binc 3000
info string remaining time: 753000 time allocated: 11295

Program received signal SIGFPE, Arithmetic exception.
0x000055555555f141 in uciMainLoop() ()
(gdb) 

[colding10]

Could you try compiling with debug flags?

I think its along the lines of
cmake .. -DCMAKE_BUILD_TYPE="Debug"

I don't have access to a computer running Linux (all apple here) so I'll try and find a way to get a Linux system running on my Mac (aarch64).
Thanks for letting me know about this issue! I'vent had a chance to work on cross-compatibility that much, so I appreciate this help.

[tissatussa]

Glad to help .. i always learn new things while solving such coding problems .. my feeling is that your code is fine, it just needs a twist .. i don't know how yet, but we'll solve it .. i didn't know about gdb, so this is my first time using it, nice .. i just compiled a new version -of your code by git clone- with debug flag :

cmake . -DCMAKE_BUILD_TYPE=Debug

executed in the root .. it builds a working binary of 3.2 Mb, while the non-debug version was only 202 Kb ?! .. nevermind .. using this binary the same way, i get this :

$ ./kingfish_v1.2.0_compiled_HP_with_debug 
uci
id name Kingfish 1.2.0
id author Colin D
uciok
ucinewgame
go wtime 603000 btime 603000 winc 3000 binc 3000
info string remaining time: 753000 time allocated: 11295
Floating point exception (core dumped)

$ gdb ./kingfish_v1.2.0_compiled_HP_with_debug 
GNU gdb (Ubuntu 12.1-0ubuntu1~22.04) 12.1
Copyright (C) 2022 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Type "show copying" and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<https://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
    <http://www.gnu.org/software/gdb/documentation/>.

For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from ./kingfish_v1.2.0_compiled_HP_with_debug...
(gdb) run
Starting program: /home/roelof/Apps/ChessEngines/Kingfish/kingfish_v1.2.0_compiled_HP_with_debug 
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
uci
id name Kingfish 1.2.0
id author Colin D
uciok
ucinewgame
go wtime 603000 btime 603000 winc 3000 binc 3000
info string remaining time: 753000 time allocated: 11295
info depth 1 score cp 0 nodes 2 nps 2000 hashfull 0 time 1 pv d2d4 
info depth 1 score cp 46 nodes 3 nps 3000 hashfull 0 time 1 pv d2d4 
info depth 1 score cp 22 nodes 637 nps 3047 hashfull 0 time 209 pv d2d4 
info depth 1 score cp 15 nodes 1393 nps 3580 hashfull 1 time 389 pv f2f4 
info depth 2 score cp 0 nodes 1395 nps 3576 hashfull 1 time 390 pv d2d4 
info depth 2 score cp 118 nodes 1436 nps 3635 hashfull 1 time 395 pv d2d4 
info depth 2 score cp 19 nodes 1572 nps 3760 hashfull 1 time 418 pv d2d4 
info depth 2 score cp 9 nodes 2344 nps 4034 hashfull 2 time 581 pv d2d4 
info depth 3 score cp 1 nodes 2397 nps 4055 hashfull 2 time 591 pv d2d4 
info depth 3 score cp 118 nodes 2440 nps 4087 hashfull 2 time 597 pv d2d4 
info depth 3 score cp 46 nodes 2471 nps 4118 hashfull 2 time 600 pv d2d4 
info depth 3 score cp 23 nodes 3815 nps 4355 hashfull 3 time 876 pv d2d4 
info depth 3 score cp 20 nodes 3838 nps 4376 hashfull 3 time 877 pv d2d4 
info depth 4 score cp 1 nodes 3894 nps 4414 hashfull 3 time 882 pv d2d4 
info depth 4 score cp 88 nodes 3937 nps 4448 hashfull 4 time 885 pv d2d4 
info depth 4 score cp 44 nodes 8047 nps 4338 hashfull 8 time 1855 pv d2d4 
info depth 4 score cp 22 nodes 15441 nps 4664 hashfull 16 time 3310 pv d2d4 
info depth 4 score cp 11 nodes 19817 nps 4637 hashfull 20 time 4273 pv d2d4 
info depth 5 score cp 0 nodes 22763 nps 4675 hashfull 23 time 4869 pv d2d4 
info depth 5 score cp 88 nodes 22806 nps 4678 hashfull 23 time 4875 pv d2d4 
info depth 5 score cp 43 nodes 24401 nps 4700 hashfull 25 time 5191 pv d2d4 
info depth 5 score cp 22 nodes 28630 nps 4756 hashfull 29 time 6019 pv d2d4 
info depth 5 score cp 32 nodes 30065 nps 4842 hashfull 30 time 6208 pv d2d4 
info depth 6 score cp 0 nodes 31637 nps 4874 hashfull 31 time 6490 pv d2d4 
info depth 6 score cp 837 nodes 32507 nps 4928 hashfull 32 time 6596 pv d2d4 
info depth 6 score cp 178 nodes 32593 nps 4939 hashfull 32 time 6598 pv d2d4 
info depth 6 score cp 88 nodes 37084 nps 5008 hashfull 36 time 7404 pv d2d4 
info depth 6 score cp 43 nodes 42827 nps 5090 hashfull 42 time 8413 pv d2d4 
info depth 6 score cp 21 nodes 68691 nps 4932 hashfull 69 time 13925 pv d2d4 
bestmove d2d4
[..]

and it doesn't run in CuteChess .. it's strange to me running under gdb is OK !? I have no explanation ..

[tissatussa]

in detail, this is what i just did in terminal to make the debug binary :

$ cmake . -DCMAKE_BUILD_TYPE=Debug
-- The C compiler identification is GNU 11.3.0
-- The CXX compiler identification is GNU 11.3.0
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /usr/bin/cc - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
Kingfish version is set to 1.2.0
-- Configuring done (0.6s)
-- Generating done (0.0s)
-- Build files have been written to: /home/roelof/Compiled/Kingfish

$ make
[ 11%] Building CXX object CMakeFiles/kingfish.dir/src/kingfish/main.cpp.o
In file included from /home/roelof/Compiled/Kingfish/src/kingfish/main.cpp:1:
/home/roelof/Compiled/Kingfish/src/kingfish/bitboard.h:26:17: warning: ‘BBS::king_attacks’ defined but not used [-Wunused-variable]
   26 | static Bitboard king_attacks[64];
      |                 ^~~~~~~~~~~~
/home/roelof/Compiled/Kingfish/src/kingfish/bitboard.h:25:17: warning: ‘BBS::knight_attacks’ defined but not used [-Wunused-variable]
   25 | static Bitboard knight_attacks[64];
      |                 ^~~~~~~~~~~~~~
/home/roelof/Compiled/Kingfish/src/kingfish/bitboard.h:24:17: warning: ‘BBS::pawn_attacks’ defined but not used [-Wunused-variable]
   24 | static Bitboard pawn_attacks[2][64]; // pawn attacks array [side][square]
      |                 ^~~~~~~~~~~~
[ 22%] Building CXX object CMakeFiles/kingfish.dir/src/kingfish/uci.cpp.o
In file included from /home/roelof/Compiled/Kingfish/src/kingfish/./ai/../position.h:10,
                 from /home/roelof/Compiled/Kingfish/src/kingfish/./ai/searcher.h:12,
                 from /home/roelof/Compiled/Kingfish/src/kingfish/uci.cpp:9:
/home/roelof/Compiled/Kingfish/src/kingfish/./ai/../piece.h:67:14: warning: ‘STARTING_POSITION’ defined but not used [-Wunused-variable]
   67 | static Piece STARTING_POSITION[64] = {
      |              ^~~~~~~~~~~~~~~~~
In file included from /home/roelof/Compiled/Kingfish/src/kingfish/./ai/../position.h:8,
                 from /home/roelof/Compiled/Kingfish/src/kingfish/./ai/searcher.h:12,
                 from /home/roelof/Compiled/Kingfish/src/kingfish/uci.cpp:9:
/home/roelof/Compiled/Kingfish/src/kingfish/./ai/../bitboard.h:26:17: warning: ‘BBS::king_attacks’ defined but not used [-Wunused-variable]
   26 | static Bitboard king_attacks[64];
      |                 ^~~~~~~~~~~~
/home/roelof/Compiled/Kingfish/src/kingfish/./ai/../bitboard.h:25:17: warning: ‘BBS::knight_attacks’ defined but not used [-Wunused-variable]
   25 | static Bitboard knight_attacks[64];
      |                 ^~~~~~~~~~~~~~
/home/roelof/Compiled/Kingfish/src/kingfish/./ai/../bitboard.h:24:17: warning: ‘BBS::pawn_attacks’ defined but not used [-Wunused-variable]
   24 | static Bitboard pawn_attacks[2][64]; // pawn attacks array [side][square]
      |                 ^~~~~~~~~~~~
[ 33%] Building CXX object CMakeFiles/kingfish.dir/src/kingfish/piece.cpp.o
In file included from /home/roelof/Compiled/Kingfish/src/kingfish/piece.cpp:1:
/home/roelof/Compiled/Kingfish/src/kingfish/piece.h:67:14: warning: ‘STARTING_POSITION’ defined but not used [-Wunused-variable]
   67 | static Piece STARTING_POSITION[64] = {
      |              ^~~~~~~~~~~~~~~~~
[ 44%] Building CXX object CMakeFiles/kingfish.dir/src/kingfish/ai/searcher.cpp.o
In file included from /home/roelof/Compiled/Kingfish/src/kingfish/ai/../position.h:10,
                 from /home/roelof/Compiled/Kingfish/src/kingfish/ai/searcher.h:12,
                 from /home/roelof/Compiled/Kingfish/src/kingfish/ai/searcher.cpp:1:
/home/roelof/Compiled/Kingfish/src/kingfish/ai/../piece.h:67:14: warning: ‘STARTING_POSITION’ defined but not used [-Wunused-variable]
   67 | static Piece STARTING_POSITION[64] = {
      |              ^~~~~~~~~~~~~~~~~
In file included from /home/roelof/Compiled/Kingfish/src/kingfish/ai/../position.h:8,
                 from /home/roelof/Compiled/Kingfish/src/kingfish/ai/searcher.h:12,
                 from /home/roelof/Compiled/Kingfish/src/kingfish/ai/searcher.cpp:1:
/home/roelof/Compiled/Kingfish/src/kingfish/ai/../bitboard.h:26:17: warning: ‘BBS::king_attacks’ defined but not used [-Wunused-variable]
   26 | static Bitboard king_attacks[64];
      |                 ^~~~~~~~~~~~
/home/roelof/Compiled/Kingfish/src/kingfish/ai/../bitboard.h:25:17: warning: ‘BBS::knight_attacks’ defined but not used [-Wunused-variable]
   25 | static Bitboard knight_attacks[64];
      |                 ^~~~~~~~~~~~~~
/home/roelof/Compiled/Kingfish/src/kingfish/ai/../bitboard.h:24:17: warning: ‘BBS::pawn_attacks’ defined but not used [-Wunused-variable]
   24 | static Bitboard pawn_attacks[2][64]; // pawn attacks array [side][square]
      |                 ^~~~~~~~~~~~
[ 55%] Building CXX object CMakeFiles/kingfish.dir/src/kingfish/ai/timemanager.cpp.o
In file included from /home/roelof/Compiled/Kingfish/src/kingfish/ai/../position.h:10,
                 from /home/roelof/Compiled/Kingfish/src/kingfish/ai/timemanager.h:7,
                 from /home/roelof/Compiled/Kingfish/src/kingfish/ai/timemanager.cpp:1:
/home/roelof/Compiled/Kingfish/src/kingfish/ai/../piece.h:67:14: warning: ‘STARTING_POSITION’ defined but not used [-Wunused-variable]
   67 | static Piece STARTING_POSITION[64] = {
      |              ^~~~~~~~~~~~~~~~~
In file included from /home/roelof/Compiled/Kingfish/src/kingfish/ai/../position.h:8,
                 from /home/roelof/Compiled/Kingfish/src/kingfish/ai/timemanager.h:7,
                 from /home/roelof/Compiled/Kingfish/src/kingfish/ai/timemanager.cpp:1:
/home/roelof/Compiled/Kingfish/src/kingfish/ai/../bitboard.h:26:17: warning: ‘BBS::king_attacks’ defined but not used [-Wunused-variable]
   26 | static Bitboard king_attacks[64];
      |                 ^~~~~~~~~~~~
/home/roelof/Compiled/Kingfish/src/kingfish/ai/../bitboard.h:25:17: warning: ‘BBS::knight_attacks’ defined but not used [-Wunused-variable]
   25 | static Bitboard knight_attacks[64];
      |                 ^~~~~~~~~~~~~~
/home/roelof/Compiled/Kingfish/src/kingfish/ai/../bitboard.h:24:17: warning: ‘BBS::pawn_attacks’ defined but not used [-Wunused-variable]
   24 | static Bitboard pawn_attacks[2][64]; // pawn attacks array [side][square]
      |                 ^~~~~~~~~~~~
[ 66%] Building CXX object CMakeFiles/kingfish.dir/src/kingfish/bitboard.cpp.o
[ 77%] Building CXX object CMakeFiles/kingfish.dir/src/kingfish/position.cpp.o
In file included from /home/roelof/Compiled/Kingfish/src/kingfish/./position.h:10,
                 from /home/roelof/Compiled/Kingfish/src/kingfish/position.cpp:1:
/home/roelof/Compiled/Kingfish/src/kingfish/./piece.h:67:14: warning: ‘STARTING_POSITION’ defined but not used [-Wunused-variable]
   67 | static Piece STARTING_POSITION[64] = {
      |              ^~~~~~~~~~~~~~~~~
In file included from /home/roelof/Compiled/Kingfish/src/kingfish/./position.h:8,
                 from /home/roelof/Compiled/Kingfish/src/kingfish/position.cpp:1:
/home/roelof/Compiled/Kingfish/src/kingfish/./bitboard.h:26:17: warning: ‘BBS::king_attacks’ defined but not used [-Wunused-variable]
   26 | static Bitboard king_attacks[64];
      |                 ^~~~~~~~~~~~
/home/roelof/Compiled/Kingfish/src/kingfish/./bitboard.h:25:17: warning: ‘BBS::knight_attacks’ defined but not used [-Wunused-variable]
   25 | static Bitboard knight_attacks[64];
      |                 ^~~~~~~~~~~~~~
/home/roelof/Compiled/Kingfish/src/kingfish/./bitboard.h:24:17: warning: ‘BBS::pawn_attacks’ defined but not used [-Wunused-variable]
   24 | static Bitboard pawn_attacks[2][64]; // pawn attacks array [side][square]
      |                 ^~~~~~~~~~~~
[ 88%] Building CXX object CMakeFiles/kingfish.dir/src/kingfish/zobrist.cpp.o
In file included from /home/roelof/Compiled/Kingfish/src/kingfish/position.h:10,
                 from /home/roelof/Compiled/Kingfish/src/kingfish/zobrist.h:8,
                 from /home/roelof/Compiled/Kingfish/src/kingfish/zobrist.cpp:1:
/home/roelof/Compiled/Kingfish/src/kingfish/piece.h:67:14: warning: ‘STARTING_POSITION’ defined but not used [-Wunused-variable]
   67 | static Piece STARTING_POSITION[64] = {
      |              ^~~~~~~~~~~~~~~~~
In file included from /home/roelof/Compiled/Kingfish/src/kingfish/position.h:8,
                 from /home/roelof/Compiled/Kingfish/src/kingfish/zobrist.h:8,
                 from /home/roelof/Compiled/Kingfish/src/kingfish/zobrist.cpp:1:
/home/roelof/Compiled/Kingfish/src/kingfish/bitboard.h:26:17: warning: ‘BBS::king_attacks’ defined but not used [-Wunused-variable]
   26 | static Bitboard king_attacks[64];
      |                 ^~~~~~~~~~~~
/home/roelof/Compiled/Kingfish/src/kingfish/bitboard.h:25:17: warning: ‘BBS::knight_attacks’ defined but not used [-Wunused-variable]
   25 | static Bitboard knight_attacks[64];
      |                 ^~~~~~~~~~~~~~
/home/roelof/Compiled/Kingfish/src/kingfish/bitboard.h:24:17: warning: ‘BBS::pawn_attacks’ defined but not used [-Wunused-variable]
   24 | static Bitboard pawn_attacks[2][64]; // pawn attacks array [side][square]
      |                 ^~~~~~~~~~~~
[100%] Linking CXX executable kingfish_1.2.0
[100%] Built target kingfish

btw. we know those warnings don't bother (but you could solve them ?)

[colding10]

yeah, this is pretty weird, i don't have much experience with this kind of stuff. I'll work on solving those warnings in the next release. maybe the problem is with different operating system/libraries?

btw I think it might not work in CuteChess because Kingfish sometimes freezes and doesn't respond to uci input while searching, this might be a problem.

thanks for still working on this with me, I appreciate the learning experience. This is my first large open-source project and I am using it to gain experiences like this.

[tissatussa]

I am using it to gain experiences like this

yeah ! Apple seems to have Linux inside .. so i'm told .. i guess my tests apply to your machine also .. you wrote 'flags', but i gave only one called -DCMAKE_BUILD_TYPE .. should more parameters be involved ? I mean to suit the machine for compiling properly ? I have just basic understanding of many compiling issues, learned by experience, with many languages and versions, while trying to compile (also weaker) chess engines .. i often succeed to adjust things by simple code edit, but not always .. eg. learning about .so files (and versions!) .. myself i mainly do Python and JS, no C(++) .. you seem to know how to use github, that's pretty difficult for me .. i'd like to learn that, i have some nice scripts to publish, concerning chess and video, maybe you can set something up for me ? just saying ..

why is the debug binary so big ? can it provide more output ? how ?

[tissatussa]

another thing .. you state :

..doesn't respond to uci input while searching..

but i wonder : what input do you mean ? I think the engine should not expect any input while calculating a next best move .. it just runs until it thinks time's up, CuteChess just waits for 'best move ..' am i right ?

[colding10]

it just runs until it thinks time's up, CuteChess just waits for 'best move ..' am i right ?

i think the UCI specification says that the engine should not hang while thinking. sometimes, the GUI (CuteChess) will need to stop a search while it is running or something like that, so this might cause problems with CuteChess. (it works on my machine however)

why is the debug binary so big ? can it provide more output ? how ?

the debug binary is bigger because it has more information like line numbers, functions, and others. this can be read by the debugger and can help with debugging. [StackOverflow question](https://stackoverflow.com/questions/41262610/why-debug-mode-file-size-is-large-than-release-mode#:~:text=The%20debug%20executables'%20large%20size,program%20or%20to%20debug%20it.)

you seem to know how to use github, that's pretty difficult for me

yeah, it was a learning curve. i recommend starting with some smaller projects and looking at large projects by other people and trying to understand workspace structure. **learning github is definitely worth it at the end, you can work on open-source projects and share your code! also, it is a must for large projects**

[tissatussa]

and can you reproduce my terminal output, using gdb ? Or are things different on Apple ? And what about those warnings during compilation ? Are they the same on Apple ? Maybe when you try to fix those warnings, both on Linux and Apple, you could notice other issues are solved too ?! When compiling older C(++) code i sometimes encounter that variables must have another type, the 64-bit kind or so, to fix issues .. just my thoughts ..

[tissatussa]

..sometimes, the GUI (CuteChess) will need to stop a search while it is running or something like that..

i try to imagine a situation like that .. stop a search may apply when a 3-fold repetition is judged by CuteChess ? Or the engine has run out of time ?

[colding10]

and can you reproduce my terminal output, using gdb ? Or are things different on Apple ? And what about those warnings during compilation ? Are they the same on Apple ? Maybe when you try to fix those warnings, both on Linux and Apple, you could notice other issues are solved too ?! When compiling older C(++) code i sometimes encounter that variables must have another type, the 64-bit kind or so, to fix issues .. just my thoughts ..

on Apple, I use lldb instead of gdb and I don't get any strange output, it works perfectly. for some reason, I also don't get warnings (I use clang instead of g++), but ill still try and resolve those warnings you are getting

[tissatussa]

well, i never used lldb but i can try .. also clang can be used my machine .. just to see differences of Linux and Apple output ? I just did the cmake concept .. how could i compile with clang ? example command ?