관심있는것들

we initialize node name "basic_shapes" and make publisher with topic name "visualization_marker" we set our frame id == "/my_frame" set namespace(ns) to "basic_shapes" and id to 0 == if a marker message is received with the same ns and id, the new marker will replace the old one. first starting shape is CUBE inside switch we keep change the shape variable to something else roslaunch using_makers..

Pentium 4's speed addiction P4 had 20stages in basic pipeline. which made it have high relative frequency. but there are limits to how deeply you can pipeline an architecture before you begin to reach a point of diminishing returns. 1. deeper pipeline means increase in instruction execution time 2. processor's clock speed must increase in proportion to tis pipeline depth regradless of the drawba..

signal == software interrupt deliverd by OS because 1. a process did something (wrong) accessed illegal memory read == SIGSEGV(11) , segment violation divide by zero == SIGFPE(8) try to execute illegal instructions == SIGILL(4) process try to write on a pipe that had been shutdown for writing or isn't connected anymore == SIGPIPE(13) 2. a process wants to tell something to another process to not..

$ wc 0file2 == $ cat >f2 op 2>err == f1 is passed as command line argument since file descriptor 1,2 is alreay redirected error message will go to err file for more explain == Bash One-Liners Explained, Part III: All about redirections (catonmat.net) Bash One-Liners Explain..

각종센서들이 여러 토픽을 /auto_drive 노드에게 보내주고 그것을 처리하여 /xycar_motor 노드에게 토픽을 쏴주어 컨트롤 하는 방식이다 YOLO 를 구성하고있는 darkent을 통해서 사람을 detect하고 lidar를 통해 거리를 측정한 정보를 /human_track 노드에 넣어주고 처리하여 xycar_motor 토픽을 발행한다. usb_cam노드에서 compress된 이미지를 안드로이드 카메라 ROS노드에게 보내준다. 안드로이드에서 방향과 속도를 입력받아서 최종적으로 xycar_mtor에게 토픽의 형태로 전달을 해준다. Base == 고정 부분 , 아래에 검은 상자 Link == 관절에 연결되는 긴 원통 부분 Joint == 링크를 연결하는 부위로 관절 부위 회전하는 방향및 한계가 존재함..

the difference happens how we smartly select edge in the case we Topologically sort the DAG and then select edges in order. since this is dag this works if graph doesn't have cycle and works for negative. in case of dijkstra we pick the edge that has the minimum priority (in this case d[u], the current shortest distance from source). dijkstra works with cycles but all the weight have to be non n..

601's pipeline has a classic 4 stage RISC integer pipeline: fetch, decode/dispatch, exectue , write back Instruction queue == is used mainly for dectecting an dealing with branches. if branch unit has enough information to resolve the branch immediately it is simply deleted from the instruction queue and replaced with the instruction located at the branch target. (branch folding) When a branch i..

1. 노드간 동기화 문제 해결 , 첫번쨰 메시지가 수신이 안되는경우 sender_serial.py 에서 pub.get_num_connection 을 통해서 1이 될떄까지 헛돌게 하면된다. 1:N의 통신도 마찬가지이다 3이될떄까지 헛돌게 하면된다. 2. 데이터 크기에 따른 전송속도는 어떻게 되는가? 큰 파일을 보낼수록 속도는 늦어진다. 3. 도착하는 데이터를 미처 처리하지 못하면 어떻게 되는가? subscriber 의 큐사이즈를 늘리면 아무리 publishing 이 빨라도 흘림없이 다 처리 할 수 있다. 4. 주기적 발송에서 타임슬롯을 오버하면 어떻게 되는가? 이런식으로 벗어나게 된다 5. ROS 노드의 순차 실행 while True 문에서 자신의 이름에 해당하는 메세지가 올떄까지 돌고있다가 인터럽트 방식..

exporting user defined variable to sub shell preprocessor == include headerfile, expand macro , remove comments , generate modfied source program. gcc -E only preprocess compiler == generate assembly program. 1. check for syntax error 2. converts source to assembly of underlying processor(x86) Assembler == generate relocatable object program. assemble to machine depend code. Linker == combine al..

pentium shares 4 stages in common : Fetch , Decode-1 , Decode-2 , Write when instruction reaches the execute phase it enters a more specialized pipeline. depth of pipeline can be different Petium's basic integer pipeline has 5 stages 1. Prefetch/Fetch == fetched from instruction cache and aligned in prefetch buffers for decoding. 2. Decode-1 == based on set of hardware-based rules instructions a..