mingbo's tech tips

the solution I got runs more than 1 second, which is terrible. Please help if you have better algorithm """ Project Euler Problem #14 ========================== The following iterative sequence is defined for the set of positive integers: n->n/2 (n is even) n->3n + 1 (n is odd) Using the rule above and starting with 13, we generate the following sequence:                   13->40->20->10->5->16->8->4->2->1 It can be seen that this sequence (starting at 13 and finishing at 1) contains 10 terms. Although it has not been proved yet (Collatz Problem), it is thought that all starting numbers finish at 1. Which starting number, under one million, produces the longest chain? NOTE: Once the chain starts the terms are allowed to go above one million. """ limit=1000000 uplimit  = limit * 3 answer = 1 maxval = 0 data = [0] * uplimit data[1] = 1 for in...

""" Project Euler Problem #12 ========================== The sequence of triangle numbers is generated by adding the natural numbers. So the 7^th triangle number would be 1 + 2 + 3 + 4 + 5 + 6 + 7 = 28. The first ten terms would be:                  1, 3, 6, 10, 15, 21, 28, 36, 45, 55, ... Let us list the factors of the first seven triangle numbers:    1: 1    3: 1,3    6: 1,2,3,6   10: 1,2,5,10   15: 1,3,5,15   21: 1,3,7,21   28: 1,2,4,7,14,28 We can see that 28 is the first triangle number to have over five divisors. What is the value of the first triangle number to have over five hundred divisors? """ limit = 100000 data=[0] * limit for i in xrange(1,int(limit/2+1)):     data[i::i] = [ x+1 for x in data[i::i]] def find():     s = 1     while True:         if s % 2 == 0:           ...

basically, when any process need to do I/O and underlying library calls io_schedule() will put CPU into iowait status and then if the CPU is idle (no other active process running), iowait time increases. below is related code snip from 3.x kernel: // in kernel/sched/cputime.c                                                                                                                                                                   /*  * Account for idle time.  * @cputime: the cpu time spent in idle wait  */ void account_idle_time(cputime_t cputime) {   ...

I searched online for answers, but none of them are good enough for me --- most of them says it's equal to running queue, but some observations on an I/O busy NFS server disagree with that. So I checked source code. TLDR;  load average can be considered as a sum of total running processes (the run queue size) and interruptible process over specific time period. This applies to at least version 2.6.x and 3.x (I only checked source code of those two versions) BTW, the uptime command is only read and output the data in /proc/loadavg for load average. (A little bit) Long but official explanation : copied from Linux kernel source code: of v3.14-rc6 /* * Global load-average calculations * * We take a distributed and async approach to calculating the global load-avg * in order to minimize overhead. * * The global load average is an exponentially decaying average of nr_running + * nr_uninterruptible. * * Once every LOAD_FREQ: * * nr_active = 0; * f...

I recently applied a NFS tag from my bank and attached it to my Android phone (Nexus 4). Then I found every time I power on (not boot up) the phone, there will be weird sound. I tried to disabled all the possible setting under sound section in settings, but the sound still there. Then I realized it may caused by the NFS tag, so I went to settings -> Wireless & networks -> more , and unchecked the "NFC" option, and the weird/annoying sound gone.

you may get URL like: for iPhone/iPad: com.rsa.securid.iphone://ctf?ctfData=nnnnnnnn for Andriod: http://127.0.0.1/securid/ctf?ctfData=nnnnnnnn you can convert between them, simply keep the ctf?ctfData=nnnnnnnn part and replace prefix, then import.

Putty is one of the best and must-have freeware for people working on Linux/Unix but use Windows as client like me.  We need to manage many servers and sometimes we are hoping we can run/execute same command on multiple host at same time, or just input same thing to multiple host. I searched online for a tool can do this. And it looks like PuTTYCS (PuTTY Command Sender) is the only one existing. But I’m a little bit disappointing after tried the software, it’s good but not good enough. It can only send command to each window one by one, and you have to wait until last window got input. So I think I should do something, and puttyCluster was born ( https://github.com/mingbowan/puttyCluster ) interface is simple: When you input Windows title pattern in the text box, you will be prompt for how many windows matching the pattern, like this: and you click the edit box under “cluster input”, what ever key you pressed will pass to all those windows simultaneously, even “Ctrl-C”, “Esc” ...