John's blog: March 2019

Thursday, 21 March 2019

Microcode for a SWAP Reg0, Reg1 (3 Clock Cycles)

For those wanted to extend their instruction set - without adding too much complexity to microcode instructions - a SWAP instruction, where two registers are swapped over - can be implemented in 3 clock cycles just by using a series of 3 exclusive-or operations between the two registers.

I'm assuming that 'setting a register' is done on the opposing edge of the exclusive-or operation. We can achieve a swap with the following microcode instructions.

SWAP A, B

A <- A XOR B CLK 1  
B <- A XOR B CLK 2
A <- A XOR B CLK 3

For example, if we start off with the two registers A and B 
A = 3, B = 32  CLK 0
A = 35, B = 32 CLK 1
A = 35, B = 3  CLK 2
A = 32, B = 3  CLK 3

I hope - someone finds this helpful!﻿

Sunday, 17 March 2019

Git Cheat Sheet

git init # initialise directory for git repos
git status # tells user what possible files need to be 'added' or what files have changed.
git add . # add all files
git add filename1 filename2 # add numerous files to git 'staging area'
git log # show log of commits with their hash codes

git diff filename # to find out difference between working directory and last commit in staging directory
git checkout filename # to revert back a particular commit (last commit ) COMPARE THIS TO BRANCH CREATION

git checkout -b branchname #

git remote add origin https://github.com/johnny/myproject.git
#git remote add <REMOTE> GIT_URL
git remote -v # check settings

git push -u origin master
git push -u <REMOTE> <BRANCH>

git clone https://github.com/johnny/myproject.git

Sunday, 10 March 2019

BootStrap Grid layout - Base 12 System

Thursday, 7 March 2019

CSS 'position' property

DOCTYPE html>
<html lang="en" dir="ltr">

<head>
<meta charset="utf-8">
<title>Colour Block Alignment with absolute position</title>
<script>
var t = 0 ;
var refresh = 24 ;
var freq = 0.33 ;
var radius = 80 ;
var centre_x = 180 ;
var centre_y = 180 ;

function onLoad() {

window.setInterval(function(){

var el = document.getElementById('animate-block');
el.style.backgroundColor = "green";

var y = centre_y + radius * Math.sin(6.3 * freq * t) ;
var x = centre_x + radius * Math.cos(6.3 * freq * t) ;

el.style.top = y + 'px' ;
el.style.left = x + 'px' ;

t += (refresh/1000)
console.log('t = ' + t) ;

}, refresh);
}

</script>
</head>

<body onload="onLoad()">

<div class='middle_container' style="background-color: purple; width:200px; height:300px;">
middle container
</div>

<div class='colourblocktest' id='animate-block' style="z-index: -1; background-color: green; width:300px; height:300px; position: absolute; left: 60px; top: 37px; ">

<div class='red' style="background-color: red; width:100px; height:100px; position: absolute; left: 200px; top: 200px">
</div>

<div class='blue' style="background-color: blue; width:100px; height:100px;position: absolute; left: 100px; top: 100px">
</div>

<div class='yellow' style="background-color: yellow; width:100px; height:100px;position: absolute; left: 0px; top: 0px">
</div>

</div>

</body>
</html>

Monday, 4 March 2019

Crude Permutations

import java.util.*;

public class Dynamic {

public int calls = 0;
public int depth = 0;

public HashMap<String,HashSet<String> > cache = new HashMap<>();
public boolean cacheCheck = true;

public HashSet<String> preIndexList(String preIndexChr, HashSet<String> list) {
// insert preindex char 'preIndexChr' to each element in list
//System.out.printf("Pre Indexing with %s lst = %s",preIndexChr,list) ;
HashSet<String> nList = new HashSet<>();
for(String ele : list) {
nList.add(preIndexChr + ele);
}
return nList;
}

// Depth
public HashSet<String> perm(String s,int dpth) {
if (dpth > depth) {
depth = dpth;
//System.out.printf("Depth %d\n",depth) ;
}
if (cacheCheck && cache.containsKey(s)) {
return cache.get(s);
}

calls++;

HashSet<String> slst = new HashSet<>();

if (s.length() == 1) {
slst.add(s);
cache.put(s,slst);
return slst;
}

for(int i = 0; i < s.length(); i++) {

String left = s.substring(0,1);
String right = s.substring(1);
slst.addAll(preIndexList(left,perm(right,dpth++)));
s = right + left;
}
cache.put(s,slst);
return slst;

}

public String buildString(int size) {
char [] ch = new char[size];
for(int i = 0; i < size; i++) {
ch[i] = (char)(65 + i);
}
return new String(ch);
}
public static void main(String [] args) {
for(int i = 1; i < 10; i++) {
Dynamic d = new Dynamic();
String s = d.buildString(i );
HashSet<String> r = d.perm(s,0);
// System.out.printf("Perm of '%s' size = %d (built with %d calls)\nLIST %s\n",s,r.size(),d.calls,r) ;
//System.out.printf("Size of HashMap %d\n",d.cache.size()) ;
//System.out.printf("Perm of '%s' size = %d (built with %d calls)\n",s,r.size(),d.calls) ;
// number of Calls can be expressed as recurance relation.
// Kn = n * Kn-1 + 1
System.out.printf("'%s' string size = %d list size = %d calls %d depth %d\n",s,s.length(),r.size(),d.calls,d.depth);
//System.out.printf("LIST %s",r) ;
}
}

}

Friday, 1 March 2019

Docker Cheat List

# Swarm App Lifecycle

## Using Secrets With Local Docker Compose

docker node ls

docker-compose up -d

docker-compose exec psql cat /run/secrets/psql_user

docker-compose 11

pcat docker-compose.yml

## Full App Lifecycle: Dev, Build and Deploy With a Single Compose Design

docker-compose up -d

docker inspect TAB COMPLETION

docker-compose down

docker-compose -f docker-compose.yml -f docker-compose.test.yml up -d

docker inspect TAB COMPLETION

docker-compose -f docker-compose.yml -f docker-compose.prod.yml config --help

docker-compose -f docker-compose.yml -f docker-compose.prod.yml config

docker-compose -f docker-compose.yml -f docker-compose.prod.yml config > output.yml

## Service Updates: Changing Things In Flight

docker service create -p 8088:80 --name web nginx:1.13.7

docker service ls

docker service scale web=5

docker service update --image nginx:1.13.6 web

docker service update --publish-rm 8088 --publish-add 9090:80

docker service update --force web

## Healthchecks in Dockerfiles

docker container run --name p1 -d postgres

docker container ls

docker container run --name p2 -d --health-cmd="pg_isready -U postgres || exit 1" postgres

docker container ls

docker container inspect p2

docker service create --name p1 postgres

docker service create --name p2 --health-cmd="pg_isready -U postgres || exit 1" postgres

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