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  • Efficient way of calculating average difference of array elements from array average value

    - by Saysmaster
    Is there a way to calculate the average distance of array elements from array average value, by only "visiting" each array element once? (I search for an algorithm) Example: Array : [ 1 , 5 , 4 , 9 , 6 ] Average : ( 1 + 5 + 4 + 9 + 6 ) / 5 = 5 Distance Array : [|1-5|, |5-5|, |4-5|, |9-5|, |6-5|] = [4 , 0 , 1 , 4 , 1 ] Average Distance : ( 4 + 0 + 1 + 4 + 1 ) / 5 = 2 The simple algorithm needs 2 passes. 1st pass) Reads and accumulates values, then divides the result by array length to calculate average value of array elements. 2nd pass) Reads values, accumulates each one's distance from the previously calculated average value, and then divides the result by array length to find the average distance of the elements from the average value of the array. The two passes are identical. It is the classic algorithm of calculating the average of a set of values. The first one takes as input the elements of the array, the second one the distances of each element from the array's average value. Calculating the average can be modified to not accumulate the values, but caclulating the average "on the fly" as we sequentialy read the elements from the array. The formula is: Compute Running Average of Array's elements ------------------------------------------- RA[i] = E[i] {for i == 1} RA[i] = RA[i-1] - RA[i-1]/i + A[i]/i { for i > 1 } Where A[x] is the array's element at position x, RA[x] is the average of the array's elements between position 1 and x (running average). My question is: Is there a similar algorithm, to calculate "on the fly" (as we read the array's elements), the average distance of the elements from the array's mean value? The problem is that, as we read the array's elements, the final average value of the array is not known. Only the running average is known. So calculating differences from the running average will not yield the correct result. I suppose, if such algorithm exists, it probably should have the "ability" to compensate, in a way, on each new element read for the error calculated as far.

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  • Weighted Average and Ratings

    - by Danten
    Maths isn't my strong point and I'm at a loss here. Basically, all I need is a simple formula that will give a weighted rating on a scale of 1 to 5. If there are very few votes, they carry less influence and the rating pressess more towards the average (in this case I want it to be 3, not the average of all other ratings). I've tried a few different bayesian implementations but these haven't worked out. I believe the graphical representation I am looking for could be shown as: ___ / ___/ Cheers

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  • How do you install a USB CD Rom drive?

    - by Matt Allen
    Hello, I recently purchased a USB CD ROM drive, but I don't know how to get it to work with my computer which runs Ubuntu 10.04. http://www.amazon.com/gp/product/B00303H908/ref=oss_product When I issue the lsusb command, it shows up as: Bus 002 Device 016: ID 05e3:0701 Genesys Logic, Inc. USB 2.0 IDE Adapter The computer doesn't recognize it automatically. How can I get this drive to show up as an actual drive on my computer? If this particular drive can't handle Linux, can you recommended one which can and provide a link to it so I can purchase it? Thanks! Update: I was asked by Scaine to run a command and report back with the output: joe@joe-laptop:~$ tail -f /var/log/kern.log Dec 29 12:51:35 joe-laptop kernel: [103190.551437] sr 7:0:0:0: [sr1] Add. Sense: Illegal mode for this track Dec 29 12:51:35 joe-laptop kernel: [103190.551446] sr 7:0:0:0: [sr1] CDB: Read(10): 28 00 00 00 00 00 00 00 02 00 Dec 29 12:51:35 joe-laptop kernel: [103190.551463] end_request: I/O error, dev sr1, sector 0 Dec 29 12:51:35 joe-laptop kernel: [103190.877542] sr 7:0:0:0: [sr1] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE Dec 29 12:51:35 joe-laptop kernel: [103190.877551] sr 7:0:0:0: [sr1] Sense Key : Illegal Request [current] Dec 29 12:51:35 joe-laptop kernel: [103190.877559] Info fld=0x0, ILI Dec 29 12:51:35 joe-laptop kernel: [103190.877562] sr 7:0:0:0: [sr1] Add. Sense: Illegal mode for this track Dec 29 12:51:35 joe-laptop kernel: [103190.877572] sr 7:0:0:0: [sr1] CDB: Read(10): 28 00 00 00 00 00 00 00 02 00 Dec 29 12:51:35 joe-laptop kernel: [103190.877588] end_request: I/O error, dev sr1, sector 0 Dec 29 13:08:46 joe-laptop kernel: [104221.558911] usb 2-2.2: USB disconnect, address 16 Then when I plugged the drive back into the computer, I got: Dec 29 13:10:29 joe-laptop kernel: [104324.668320] usb 2-2.2: new high speed USB device using ehci_hcd and address 17 Dec 29 13:10:29 joe-laptop kernel: [104324.761702] usb 2-2.2: configuration #1 chosen from 1 choice Dec 29 13:10:29 joe-laptop kernel: [104324.762700] scsi8 : SCSI emulation for USB Mass Storage devices Dec 29 13:10:29 joe-laptop kernel: [104324.762935] usb-storage: device found at 17 Dec 29 13:10:29 joe-laptop kernel: [104324.762938] usb-storage: waiting for device to settle before scanning Dec 29 13:10:34 joe-laptop kernel: [104329.760521] usb-storage: device scan complete Dec 29 13:10:34 joe-laptop kernel: [104329.761344] scsi 8:0:0:0: CD-ROM TEAC CD-224E 1.7A PQ: 0 ANSI: 0 CCS Dec 29 13:10:34 joe-laptop kernel: [104329.767425] sr1: scsi3-mmc drive: 24x/24x cd/rw xa/form2 cdda tray Dec 29 13:10:34 joe-laptop kernel: [104329.767612] sr 8:0:0:0: Attached scsi CD-ROM sr1 Dec 29 13:10:34 joe-laptop kernel: [104329.767720] sr 8:0:0:0: Attached scsi generic sg2 type 5 Dec 29 13:10:34 joe-laptop kernel: [104330.141060] sr 8:0:0:0: [sr1] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE Dec 29 13:10:34 joe-laptop kernel: [104330.141069] sr 8:0:0:0: [sr1] Sense Key : Illegal Request [current] Dec 29 13:10:34 joe-laptop kernel: [104330.141077] Info fld=0x0, ILI Dec 29 13:10:34 joe-laptop kernel: [104330.141081] sr 8:0:0:0: [sr1] Add. Sense: Illegal mode for this track Dec 29 13:10:34 joe-laptop kernel: [104330.141090] sr 8:0:0:0: [sr1] CDB: Read(10): 28 00 00 00 00 00 00 00 02 00 Dec 29 13:10:34 joe-laptop kernel: [104330.141106] end_request: I/O error, dev sr1, sector 0 Dec 29 13:10:34 joe-laptop kernel: [104330.141113] __ratelimit: 18 callbacks suppressed There was more output than this (the number of lines started growing after the drive was plugged back in, and kept growing), but this is the first few lines.

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  • High load average, low CPU and IO (Centos 5.7)

    - by Ben
    A Drupal 7 site with CiviCRM, after running smoothly for a year on a 1&1 VPS suddenly became unresponsive. Now pages eventually load, but can take more than a minute. Looking at resource use in Virtuozzo, the load average carries a warning, and has remained above 1. While I understand this isn't particularly high, this is a change from when the site was working. Here is a typical snapshot of top: top - 03:10:32 up 3:21, 1 user, load average: 1.16, 1.22, 1.30 Tasks: 43 total, 1 running, 42 sleeping, 0 stopped, 0 zombie Cpu(s): 0.1%us, 0.1%sy, 0.1%ni, 99.7%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 2097152k total, 1015112k used, 1082040k free, 0k buffers Swap: 0k total, 0k used, 0k free, 0k cached CPU idle level never seems to go much below 70%. wa is virtually always at 0. There appears to be lots of free memory. And here is some vmstat output, again showign wa at 0, plenty of free memory, and an idle CPU: procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------ r b swpd free buff cache si so bi bo in cs us sy id wa st 2 0 0 1100872 0 0 0 0 2783 23672 0 538 1 0 99 0 0 1 0 0 1100872 0 0 0 0 0 16 0 101754 0 0 100 0 0 0 0 0 1100872 0 0 0 0 0 17 0 103133 0 0 100 0 0 0 0 0 1100872 0 0 0 0 0 1 0 102080 0 0 100 0 0 1 0 0 1100872 0 0 0 0 0 6 0 99881 0 0 100 0 0 0 0 0 1100872 0 0 0 0 0 1 0 105187 0 0 100 0 0 I've spoken to 1&1 but they don't have any ideas as to what could be causing the high load average. Instead they suggested an upgrade :) I've looked for processes that might be causing this, examined MySQL showprocesslist, and restarted the container with no result. Does anyone have more troubleshooting suggestions or insights?

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  • What is causing the unusual high load average?

    - by James
    I noticed on Tuesday night of last week, the load average went up sharply and it seemed abnormal since the traffic is small. Usually, the numbers usually average around .40 or lower and my server stuff (mysql, php and apache) are optimized. I noticed that the IOWait is unusually high even though the processes is barely using any CPU. top - 01:44:39 up 1 day, 21:13, 1 user, load average: 1.41, 1.09, 0.86 Tasks: 60 total, 1 running, 59 sleeping, 0 stopped, 0 zombie Cpu0 : 0.0%us, 0.0%sy, 0.0%ni,100.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu1 : 0.0%us, 0.0%sy, 0.0%ni,100.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu2 : 0.0%us, 0.3%sy, 0.0%ni, 99.7%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu3 : 0.0%us, 0.0%sy, 0.0%ni,100.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu4 : 0.0%us, 0.0%sy, 0.0%ni,100.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu5 : 0.0%us, 0.0%sy, 0.0%ni,100.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu6 : 0.0%us, 0.0%sy, 0.0%ni,100.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu7 : 0.0%us, 0.0%sy, 0.0%ni, 91.5%id, 8.5%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 1048576k total, 331944k used, 716632k free, 0k buffers Swap: 0k total, 0k used, 0k free, 0k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 1 root 15 0 2468 1376 1140 S 0 0.1 0:00.92 init 1656 root 15 0 13652 5212 664 S 0 0.5 0:00.00 apache2 9323 root 18 0 13652 5212 664 S 0 0.5 0:00.00 apache2 10079 root 18 0 3972 1248 972 S 0 0.1 0:00.00 su 10080 root 15 0 4612 1956 1448 S 0 0.2 0:00.01 bash 11298 root 15 0 13652 5212 664 S 0 0.5 0:00.00 apache2 11778 chikorit 15 0 2344 1092 884 S 0 0.1 0:00.05 top 15384 root 18 0 17544 13m 1568 S 0 1.3 0:02.28 miniserv.pl 15585 root 15 0 8280 2736 2168 S 0 0.3 0:00.02 sshd 15608 chikorit 15 0 8280 1436 860 S 0 0.1 0:00.02 sshd Here is the VMStat procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu---- r b swpd free buff cache si so bi bo in cs us sy id wa 1 0 0 768644 0 0 0 0 14 23 0 10 1 0 99 0 IOStat - Nothing unusal Total DISK READ: 67.13 K/s | Total DISK WRITE: 0.00 B/s TID PRIO USER DISK READ DISK WRITE SWAPIN IO COMMAND 19496 be/4 chikorit 11.85 K/s 0.00 B/s 0.00 % 0.00 % apache2 -k start 19501 be/4 mysql 3.95 K/s 0.00 B/s 0.00 % 0.00 % mysqld 19568 be/4 chikorit 11.85 K/s 0.00 B/s 0.00 % 0.00 % apache2 -k start 19569 be/4 chikorit 11.85 K/s 0.00 B/s 0.00 % 0.00 % apache2 -k start 19570 be/4 chikorit 11.85 K/s 0.00 B/s 0.00 % 0.00 % apache2 -k start 19571 be/4 chikorit 7.90 K/s 0.00 B/s 0.00 % 0.00 % apache2 -k start 19573 be/4 chikorit 7.90 K/s 0.00 B/s 0.00 % 0.00 % apache2 -k start 1 be/4 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % init 11778 be/4 chikorit 0.00 B/s 0.00 B/s 0.00 % 0.00 % top 19470 be/4 mysql 0.00 B/s 0.00 B/s 0.00 % 0.00 % mysqld Load Average Chart - http://i.stack.imgur.com/kYsD0.png I want to be sure if this is not a MySQL problem before making sure. Also, this is a Ubuntu 10.04 LTS Server on OpenVZ. Edit: This will probably give a good picture on the IO Wait top - 22:12:22 up 17:41, 1 user, load average: 1.10, 1.09, 0.93 Tasks: 33 total, 1 running, 32 sleeping, 0 stopped, 0 zombie Cpu(s): 0.6%us, 0.2%sy, 0.0%ni, 89.0%id, 10.1%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 1048576k total, 260708k used, 787868k free, 0k buffers Swap: 0k total, 0k used, 0k free, 0k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 1 root 15 0 2468 1376 1140 S 0 0.1 0:00.88 init 5849 root 15 0 12336 4028 668 S 0 0.4 0:00.00 apache2 8063 root 15 0 12336 4028 668 S 0 0.4 0:00.00 apache2 9732 root 16 0 8280 2728 2168 S 0 0.3 0:00.02 sshd 9746 chikorit 18 0 8412 1444 864 S 0 0.1 0:01.10 sshd 9747 chikorit 18 0 4576 1960 1488 S 0 0.2 0:00.24 bash 13706 chikorit 15 0 2344 1088 884 R 0 0.1 0:00.03 top 15745 chikorit 15 0 12968 5108 1280 S 0 0.5 0:00.00 apache2 15751 chikorit 15 0 72184 25m 18m S 0 2.5 0:00.37 php5-fpm 15790 chikorit 18 0 12472 4640 1192 S 0 0.4 0:00.00 apache2 15797 chikorit 15 0 72888 23m 16m S 0 2.3 0:00.06 php5-fpm 16038 root 15 0 67772 2848 592 D 0 0.3 0:00.00 php5-fpm 16309 syslog 18 0 24084 1316 992 S 0 0.1 0:00.07 rsyslogd 16316 root 15 0 5472 908 500 S 0 0.1 0:00.00 sshd 16326 root 15 0 2304 908 712 S 0 0.1 0:00.02 cron 17464 root 15 0 10252 7560 856 D 0 0.7 0:01.88 psad 17466 root 18 0 1684 276 208 S 0 0.0 0:00.31 psadwatchd 17559 root 18 0 11444 2020 732 S 0 0.2 0:00.47 sendmail-mta 17688 root 15 0 10252 5388 1136 S 0 0.5 0:03.81 python 17752 teamspea 19 0 44648 7308 4676 S 0 0.7 1:09.70 ts3server_linux 18098 root 15 0 12336 6380 3032 S 0 0.6 0:00.47 apache2 18099 chikorit 18 0 10368 2536 464 S 0 0.2 0:00.00 apache2 18120 ntp 15 0 4336 1316 984 S 0 0.1 0:00.87 ntpd 18379 root 15 0 12336 4028 668 S 0 0.4 0:00.00 apache2 18387 mysql 15 0 62796 36m 5864 S 0 3.6 1:43.26 mysqld 19584 root 15 0 12336 4028 668 S 0 0.4 0:00.02 apache2 22498 root 16 0 12336 4028 668 S 0 0.4 0:00.00 apache2 24260 root 15 0 67772 3612 1356 S 0 0.3 0:00.22 php5-fpm 27712 root 15 0 12336 4028 668 S 0 0.4 0:00.00 apache2 27730 root 15 0 12336 4028 668 S 0 0.4 0:00.00 apache2 30343 root 15 0 12336 4028 668 S 0 0.4 0:00.00 apache2 30366 root 15 0 12336 4028 668 S 0 0.4 0:00.00 apache2 This is the free ram as of today. total used free shared buffers cached Mem: 1024 302 721 0 0 0 -/+ buffers/cache: 302 721 Swap: 0 0 0 Update: Looking into the logs, particularly the PHP5-FPM, which is causing the CPU spike. I found that its segment faulting for some apparent reason. [03-Jun-2012 06:11:20] NOTICE: [pool www] child 14132 started [03-Jun-2012 06:11:25] WARNING: [pool www] child 13664 exited on signal 11 (SIGSEGV) after 53.686322 seconds from start [03-Jun-2012 06:11:25] NOTICE: [pool www] child 14328 started [03-Jun-2012 06:11:25] WARNING: [pool www] child 14132 exited on signal 11 (SIGSEGV) after 4.708681 seconds from start [03-Jun-2012 06:11:25] NOTICE: [pool www] child 14329 started [03-Jun-2012 06:11:58] WARNING: [pool www] child 14328 exited on signal 11 (SIGSEGV) after 32.981228 seconds from start [03-Jun-2012 06:11:58] NOTICE: [pool www] child 15745 started [03-Jun-2012 06:12:25] WARNING: [pool www] child 15745 exited on signal 11 (SIGSEGV) after 27.442864 seconds from start [03-Jun-2012 06:12:25] NOTICE: [pool www] child 17446 started [03-Jun-2012 06:12:25] WARNING: [pool www] child 14329 exited on signal 11 (SIGSEGV) after 60.411278 seconds from start [03-Jun-2012 06:12:25] NOTICE: [pool www] child 17447 started [03-Jun-2012 06:13:02] WARNING: [pool www] child 17446 exited on signal 11 (SIGSEGV) after 36.746793 seconds from start [03-Jun-2012 06:13:02] NOTICE: [pool www] child 18133 started [03-Jun-2012 06:13:48] WARNING: [pool www] child 17447 exited on signal 11 (SIGSEGV) after 82.710107 seconds from start I'm thinking that this might be causing the problem. If that is the cause, probably switching it off that to fastcgi/fcgid might resolve it... but still, I want to see if something else might be causing it to do this.

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  • How to understand the memory usage and load average in linux server

    - by Tim
    Hi, I am using a linux server which has 128GB of memory and 24 cores. I use top to see how much it is used. Its output is pasted at the end of the post. Here are two questions: (1) I see that each of the running processes occupies a very small percentage of memory (%MEM no more than 0.2%, and most just 0.0%), but how the total memory is almost used as in the fourth line of output ("Mem: 130766620k total, 130161072k used, 605548k free, 919300k buffers")? The sum of used percentage of memory over all processes seems unlikely to achieve almost 100%, doesn't it? (2) how to understand the load average on the first line ("load average: 14.04, 14.02, 14.00")? Thanks and regards! Edit: Thanks! I also really like to hear some rough numbers based on used percentage of memory to determine if a server is heavily loaded, since I once became the one who cramed the server without understanding the current load. Is swap regarded as almost the same as memory? For example, when memory and swap are almost of same size, if the memory is almost running out but the swap is still largely free, may I just view it as if the used percentage of memory + swap is still not high and run other new processes? How would you consider together CPU or memory (or memory + swap) usage? Do you become worried if either of them reaches too high or both? Output of top: $ top top - 12:45:33 up 19 days, 23:11, 18 users, load average: 14.04, 14.02, 14.00 Tasks: 484 total, 12 running, 472 sleeping, 0 stopped, 0 zombie Cpu(s): 36.7%us, 19.7%sy, 0.0%ni, 43.6%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 130766620k total, 130161072k used, 605548k free, 919300k buffers Swap: 63111312k total, 500556k used, 62610756k free, 124437752k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 6529 sanchez 18 -2 1075m 219m 13m S 100 0.2 13760:23 MATLAB 13210 timothy 18 -2 48336 37m 1216 R 100 0.0 3:56.75 absurdity 13888 timothy 18 -2 48336 37m 1204 R 100 0.0 2:04.89 absurdity 14542 timothy 18 -2 48336 37m 1196 R 100 0.0 1:08.34 absurdity 14544 timothy 18 -2 2888 2076 400 R 100 0.0 1:06.14 gatherData 6183 sanchez 18 -2 1133m 195m 13m S 100 0.2 13676:04 MATLAB 6795 sanchez 18 -2 1079m 210m 13m S 100 0.2 13734:26 MATLAB 10178 timothy 18 -2 48336 37m 1204 R 100 0.0 11:33.93 absurdity 12438 timothy 18 -2 48336 37m 1216 R 100 0.0 5:38.17 absurdity 13661 timothy 18 -2 48336 37m 1216 R 100 0.0 2:44.13 absurdity 14098 timothy 18 -2 48336 37m 1204 R 100 0.0 1:58.31 absurdity 14335 timothy 18 -2 48336 37m 1196 R 100 0.0 1:08.93 absurdity 14765 timothy 18 -2 48336 37m 1196 R 99 0.0 0:32.57 absurdity 13445 timothy 18 -2 48336 37m 1216 R 99 0.0 3:01.37 absurdity 28990 root 20 0 0 0 0 S 2 0.0 65:50.21 pdflush 12141 tim 18 -2 19380 1660 1024 R 1 0.0 0:04.04 top 1240 root 15 -5 0 0 0 S 0 0.0 16:07.11 kjournald 9019 root 20 0 296m 4460 2616 S 0 0.0 82:19.51 kdm_greet 1 root 20 0 4028 728 592 S 0 0.0 0:03.11 init 2 root 15 -5 0 0 0 S 0 0.0 0:00.00 kthreadd 3 root RT -5 0 0 0 S 0 0.0 0:01.01 migration/0 4 root 15 -5 0 0 0 S 0 0.0 0:08.13 ksoftirqd/0 5 root RT -5 0 0 0 S 0 0.0 0:00.00 watchdog/0 6 root RT -5 0 0 0 S 0 0.0 17:27.31 migration/1 7 root 15 -5 0 0 0 S 0 0.0 0:01.21 ksoftirqd/1 8 root RT -5 0 0 0 S 0 0.0 0:00.00 watchdog/1 9 root RT -5 0 0 0 S 0 0.0 10:02.56 migration/2 10 root 15 -5 0 0 0 S 0 0.0 0:00.34 ksoftirqd/2 11 root RT -5 0 0 0 S 0 0.0 0:00.00 watchdog/2 12 root RT -5 0 0 0 S 0 0.0 4:29.53 migration/3 13 root 15 -5 0 0 0 S 0 0.0 0:00.34 ksoftirqd/3

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  • C# average function without overflow exception

    - by Ron Klein
    .NET Framework 3.5. I'm trying to calculate the average of some pretty large numbers. For instance: using System; using System.Linq; class Program { static void Main(string[] args) { var items = new long[] { long.MaxValue - 100, long.MaxValue - 200, long.MaxValue - 300 }; try { var avg = items.Average(); Console.WriteLine(avg); } catch (OverflowException ex) { Console.WriteLine("can't calculate that!"); } Console.ReadLine(); } } Obviously, the mathematical result is 9223372036854775607 (long.MaxValue - 200), but I get an exception there. This is because the implementation (on my machine) to the Average extension method, as inspected by .NET Reflector is: public static double Average(this IEnumerable<long> source) { if (source == null) { throw Error.ArgumentNull("source"); } long num = 0L; long num2 = 0L; foreach (long num3 in source) { num += num3; num2 += 1L; } if (num2 <= 0L) { throw Error.NoElements(); } return (((double) num) / ((double) num2)); } I know I can use a BigInt library (yes, I know that it is included in .NET Framework 4.0, but I'm tied to 3.5). But I still wonder if there's a pretty straight forward implementation of calculating the average of integers without an external library. Do you happen to know about such implementation? Thanks!! UPDATE: The previous example, of three large integers, was just an example to illustrate the overflow issue. The question is about calculating an average of any set of numbers which might sum to a large number that exceeds the type's max value. Sorry about this confusion. I also changed the question's title to avoid additional confusion. Thanks all!!

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  • Average function without overflow exception

    - by Ron Klein
    .NET Framework 3.5. I'm trying to calculate the average of some pretty large numbers. For instance: using System; using System.Linq; class Program { static void Main(string[] args) { var items = new long[] { long.MinValue + 100, long.MinValue + 200, long.MinValue + 300 }; try { var avg = items.Average(); Console.WriteLine(avg); } catch (OverflowException ex) { Console.WriteLine("can't calculate that!"); } Console.ReadLine(); } } Obviously, the mathematical result is 9223372036854775607 (long.MaxValue - 200), but I get an exception there. This is because the implementation (on my machine) to the Average extension method, as inspected by .NET Reflector is: public static double Average(this IEnumerable<long> source) { if (source == null) { throw Error.ArgumentNull("source"); } long num = 0L; long num2 = 0L; foreach (long num3 in source) { num += num3; num2 += 1L; } if (num2 <= 0L) { throw Error.NoElements(); } return (((double) num) / ((double) num2)); } I know I can use a BigInt library (yes, I know that it is included in .NET Framework 4.0, but I'm tied to 3.5). But I still wonder if there's a pretty straight forward implementation of calculating the average of integers without an external library. Do you happen to know about such implementation? Thanks!! UPDATE: The previous example, of three large integers, was just an example to illustrate the overflow issue. The question is about calculating an average of any set of numbers which might sum to a large number that exceeds the type's max value. Sorry about this confusion. I also changed the question's title to avoid additional confusion. Thanks all!!

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  • raid 1 and high load average

    - by melocoton
    i have a server with high load average, I think the problem is the raid 1. cat /proc/mdstat Personalities : [raid1] md0 : active raid1 sdb1[1] sda1[0] 256896 blocks [2/2] [UU] md3 : active raid1 sdb3[1] sda3[0] 2562240 blocks [2/2] [UU] md4 : active raid1 sdb5[1] sda5[0] 958566272 blocks [2/2] [UU] md1 : active raid1 sdb2[1] sda2[0] 15366080 blocks [2/2] [UU] model name : Intel(R) Core(TM)2 Duo CPU E8400 @ 3.00GHz Linux 2.6.18-164.6.1.el5.centos.plus (local) 04/19/2010 avg-cpu: %user %nice %system %iowait %steal %idle 17.37 0.01 6.02 26.17 0.00 50.43 Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn sda 61.09 562.65 893.73 1557214 2473546 sda1 0.01 0.27 0.02 751 42 sda2 6.11 195.50 169.78 541075 469888 sda3 0.01 0.23 0.00 641 0 sda4 0.00 0.01 0.00 18 0 sda5 54.96 366.54 723.94 1014449 2003616 sdb 54.40 433.22 893.73 1199015 2473546 sdb1 0.01 0.16 0.02 436 42 sdb2 5.31 169.00 169.78 467729 469888 sdb3 0.01 0.31 0.00 865 0 sdb4 0.00 0.00 0.00 10 0 sdb5 49.05 263.65 723.94 729695 2003616 md1 29.96 364.39 166.68 1008498 461312 md4 124.15 630.07 713.28 1743822 1974112 md3 0.05 0.43 0.00 1192 0 md0 0.04 0.32 0.00 872 10 dm-0 7.96 83.29 23.02 230530 63720 dm-1 3.67 51.81 2.73 143394 7560 dm-2 7.63 67.76 27.35 187546 75696 dm-3 8.20 134.60 14.02 372514 38792 dm-4 5.90 10.66 39.35 29498 108912 dm-5 17.39 24.52 121.79 67850 337080 dm-6 27.19 229.60 139.89 635442 387168 dm-7 0.14 1.07 0.28 2970 776 dm-8 25.84 4.23 202.89 11698 561536 dm-9 14.77 8.38 112.35 23202 310960 dm-10 5.29 12.78 29.55 35376 81784 dm-11 0.16 1.25 0.05 3450 128 the server runs lvm in the md4

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  • 0% CPU in top for all processes, but load average > 1

    - by chrisdew
    On two different servers (with Ubuntu 12.04LTS AMD64) I have seen the following behaviour: op - 10:50:05 up 305 days, 21:17, 1 user, load average: 1.94, 2.52, 2.97 Tasks: 141 total, 2 running, 139 sleeping, 0 stopped, 0 zombie Cpu(s): 41.5%us, 6.5%sy, 0.0%ni, 51.8%id, 0.0%wa, 0.2%hi, 0.1%si, 0.0%st Mem: 8178432k total, 5753740k used, 2424692k free, 159480k buffers Swap: 15625208k total, 0k used, 15625208k free, 4905292k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 1 root 20 0 23928 2072 1216 S 0 0.0 0:56.42 init 2 root 20 0 0 0 0 S 0 0.0 0:00.01 kthreadd 3 root RT 0 0 0 0 S 0 0.0 0:01.23 migration/0 4 root 20 0 0 0 0 S 0 0.0 2:39.82 ksoftirqd/0 5 root RT 0 0 0 0 S 0 0.0 0:00.00 watchdog/0 6 root RT 0 0 0 0 S 0 0.0 0:02.99 migration/1 7 root 20 0 0 0 0 S 0 0.0 2:32.15 ksoftirqd/1 8 root RT 0 0 0 0 S 0 0.0 0:00.00 watchdog/1 9 root RT 0 0 0 0 S 0 0.0 0:11.67 migration/2 10 root 20 0 0 0 0 S 0 0.0 29:00.34 ksoftirqd/2 The server is working fine, but top shows all processes as using 0% CPU. A reboot fixed this on an earlier machine, but I haven't yet tried it on this one. I have tried top several times, and so am sure that I haven't accidentally pressed '<' or '' to sort by a different column. Sorting the process list by all of the available columns, stills shows 0% CPU for all displayed processes. What is going on? If this a kernel bug? Update: If I use top -p <PID> for a know, busy process, top still displays 0% CPU for that process.

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  • C# average function for large numbers without overflow exception

    - by Ron Klein
    .NET Framework 3.5. I'm trying to calculate the average of some pretty large numbers. For instance: using System; using System.Linq; class Program { static void Main(string[] args) { var items = new long[] { long.MaxValue - 100, long.MaxValue - 200, long.MaxValue - 300 }; try { var avg = items.Average(); Console.WriteLine(avg); } catch (OverflowException ex) { Console.WriteLine("can't calculate that!"); } Console.ReadLine(); } } Obviously, the mathematical result is 9223372036854775607 (long.MaxValue - 200), but I get an exception there. This is because the implementation (on my machine) to the Average extension method, as inspected by .NET Reflector is: public static double Average(this IEnumerable<long> source) { if (source == null) { throw Error.ArgumentNull("source"); } long num = 0L; long num2 = 0L; foreach (long num3 in source) { num += num3; num2 += 1L; } if (num2 <= 0L) { throw Error.NoElements(); } return (((double) num) / ((double) num2)); } I know I can use a BigInt library (yes, I know that it is included in .NET Framework 4.0, but I'm tied to 3.5). But I still wonder if there's a pretty straight forward implementation of calculating the average of integers without an external library. Do you happen to know about such implementation? Thanks!!

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  • Get `n` random values between 2 numbers having average `x`

    - by Somnath Muluk
    I want to get n random numbers(e.g n=16)(whole numbers) between 1 to 5(including both) so that average is x. x can be any value between (1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5). I am using PHP. e.g. Suppose I have average x= 3. Then required 16 whole numbers between 1 to 5(including both). like (1,5,3,3,3,3,2,4,2,4,1,5,1,5,3,3) Update: if x=3.5 means average of 16 numbers should be between 3.5 to 4. and if x=4 means average of 16 numbers should be between 4 to 4.5 and if x=5 means all numbers are 5

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  • How is IObservable<double>.Average supposed to work?

    - by Dan Tao
    Update Looks like Jon Skeet was right (big surprise!) and the issue was with my assumption about the Average extension providing a continuous average (it doesn't). For the behavior I'm after, I wrote a simple ContinuousAverage extension method, the implementation of which I am including here for the benefit of others who may want something similar: public static class ObservableExtensions { private class ContinuousAverager { private double _mean; private long _count; public ContinuousAverager() { _mean = 0.0; _count = 0L; } // undecided whether this method needs to be made thread-safe or not // seems that ought to be the responsibility of the IObservable (?) public double Add(double value) { double delta = value - _mean; _mean += (delta / (double)(++_count)); return _mean; } } public static IObservable<double> ContinousAverage(this IObservable<double> source) { var averager = new ContinuousAverager(); return source.Select(x => averager.Add(x)); } } I'm thinking of going ahead and doing something like the above for the other obvious candidates as well -- so, ContinuousCount, ContinuousSum, ContinuousMin, ContinuousMax ... perhaps ContinuousVariance and ContinuousStandardDeviation as well? Any thoughts on that? Original Question I use Rx Extensions a little bit here and there, and feel I've got the basic ideas down. Now here's something odd: I was under the impression that if I wrote this: var ticks = Observable.FromEvent<QuoteEventArgs>(MarketDataProvider, "MarketTick"); var bids = ticks .Where(e => e.EventArgs.Quote.HasBid) .Select(e => e.EventArgs.Quote.Bid); var bidsSubscription = bids.Subscribe( b => Console.WriteLine("Bid: {0}", b) ); var avgOfBids = bids.Average(); var avgOfBidsSubscription = avgOfBids.Subscribe( b => Console.WriteLine("Avg Bid: {0}", b) ); I would get two IObservable<double> objects (bids and avgOfBids); one would basically be a stream of all the market bids from my MarketDataProvider, the other would be a stream of the average of these bids. So something like this: Bid Avg Bid 1 1 2 1.5 1 1.33 2 1.5 It seems that my avgOfBids object isn't doing anything. What am I missing? I think I've probably misunderstood what Average is actually supposed to do. (This also seems to be the case for all of the aggregate-like extension methods on IObservable<T> -- e.g., Max, Count, etc.)

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  • Real average filesize in a set of files...

    - by JD
    Hi, I have an apparently "simple" problem but I can't find the solution for some reason... I have n millions files of different sizes and I want to find the average filesize. To simplify it, I grouped them in multiples of 16KB. < 16 KB = 18689546 files < 32 KB = 1365713 files < 48 KB = 1168186 files ... Of course, the simple (total_size / number of files) does not work. It gives an average of 291KB... What would be the algorithm to calculate the real average...? Thx, JD

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  • Weighted Average with LINQ

    - by jsmith
    My goal is to get a weighted average from one table, based on another tables primary key. Example Data: Table1 Key WEIGHTED_AVERAGE 0200 0 Table2 ForeignKey LENGTH PCR 0200 105 52 0200 105 60 0200 105 54 0200 105 -1 0200 47 55 I need to get a weighted average based on the length of a segment and I need to ignore values of -1. I know how to do this in SQL, but my goal is to do this in LINQ. It looks something like this in SQL: SELECT Sum(t2.PCR*t2.LENGTH)/Sum(t2.LENGTH) AS WEIGHTED_AVERAGE FROM Table1 t1, Table2 t2 WHERE t2.PCR <> -1 AND t2.ForeinKey = t1.Key; I am still pretty new to LINQ, and having a hard time figuring out how I would translate this. The result weighted average should come out to roughly 55.3. Thank you.

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  • Calculating moving average/stdev in SAS?

    - by John
    Hye guys, I included a screenshot to help clarify my problem: http://i40.tinypic.com/mcrnmv.jpg. I'm trying to calculate some kind of moving average and moving standard deviation. The thing is I want to calculate the coefficients of variation (stdev/avg) for the actual value. Normally this is done by calculating the stdev and avg for the past 5 years. However sometimes there will be observations in my database for which I do not have the information of the past 5 years (maybe only 3, 2 etc). That's why i want a code that will calculate the avg and stdev even if there is no information for the whole 5 years. Also, as you see in the observations, sometimes I have information over more than 5 years, when this is the case I need some kind of moving average which allows me to calculate the avg and stdev for the past 5 year. So if a company has information for 7 years I need some kind of code that will calculate the avg and stdev for, lets say, 1997 (by 1991-1996), 1998 (by 1992-1997) and 1999 (1993-1998). As i'm not very familiar with sas commands it should look (very very roughly) like: set var if year = i then stdev=stdev(year(i-6) untill year(i-1)) and average = avg(year(i-6) untill year(i-1)) Or something like this, I really have no clue, I'm gonna try and figure it out but it's worth posting it if I won't find it myself. Thanks!

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  • Simple average calculation

    - by sasquatch90
    I'm trying to write program calculating average of given numbers stored in an array. Amount of numbers should be not more than 100, and user should input them until a !int variable is given : #include <iostream> #include <conio.h> using namespace std; double average(int tab[], int i){ int sum=0; for(int j=0; j<i; ++j){ sum+=tab[j]; } return (double)sum/i; } int main() { int tab[100]; int n=0; int number=0; do { if(n < 100){ cout << "Give " << n+1 << " number : "; cin >> number; tab[n]=number; number=0; ++n; } else{ break; } } while( !isdigit(number) ); cout << average(tab, n) << endl; getch(); return 0; } Why after giving char, it prints me 'Give n number:' for all empty cells of my array ? It should end and use only given numbers.

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  • Finding the lowest average Hamming distance when the order of the strings matter

    - by user1049697
    I have a sequence of binary strings that I want to find a match for among a set of longer sequences of binary strings. A match means that the compared sequence gives the lowest average Hamming distance when all elements in the shorter sequence have been matched against a sequence in one of the longer sets. Let me try to explain with an example. I have a set of video frames that have been hashed using a perceptual hashing algorithm so that the video frames that look the same has roughly the same hash. I want to match a short video clip against a set of longer videos, to see if the clip is contained in one of these. This means that I need to find out where the sequence of the hashed frames in the short video has the lowest average Hamming distance when compared with the long videos. The short video is the sub strings Sub1, Sub2 and Sub3, and I want to match them against the hashes of the long videos in Src. The clue here is that the strings need to match in the specific order that they are given in, e.g. that Sub1 always has to match the element before Sub2, and Sub2 always has to match the element before Sub3. In this example it would map thusly: Sub1-Src3, Sub2-Src4 and Sub3-Src5. So the question is this: is there an algorithm for finding the lowest average Hamming distance when the order of the elements compared matter? The naïve approach to compare the substring sequence to every source string won't cut it of course, so I need something that preferably can match a (much) shorter sub string to a set of million of elements. I have looked at MVP-trees, BK-trees and similar, but everything seems to only take into account one binary string and not a sequence of them. Sub1: 100111011111011101 Sub2: 110111000010010100 Sub3: 111111010110101101 Src1: 001011010001010110 Src2: 010111101000111001 Src3: 101111001110011101 Src4: 010111100011010101 Src5: 001111010110111101 Src6: 101011111111010101 I have added a calculation of the examples below. (The Hamming distances aren't correct, but it doesn't matter) **Run 1.** dist(Sub1, Src1) = 8 dist(Sub2, Src2) = 10 dist(Sub3, Src3) = 12 average = 10 **Run 2.** dist(Sub1, Src2) = 10 dist(Sub2, Src3) = 12 dist(Sub3, Src4) = 10 average = 11 **Run 3.** dist(Sub1, Src3) = 7 dist(Sub2, Src4) = 6 dist(Sub3, Src5) = 10 average = 8 **Run 4.** dist(Sub1, Src3) = 10 dist(Sub2, Src4) = 4 dist(Sub3, Src5) = 2 average = 5 So the winner here is sequence 4 with an average distance of 5.

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  • Devfish Joe Healy in Fort Lauderdale - Cloud Computing and Azure - 03/11/2010 MSDN Tiki Hut

    - by Rainer
    Devfish Joe Healy, Brian Hitney, and Herve Rogero presented excellent sessions on today's MSDN Tiki Hut Event about  Cloud Computing and Azure. This was an developer focused event, starting out with an overview about structure and platform, followed by working code samples running on the platform, and all needed information to get developers started on development for cloud applications. Participants had Q&A opportunities after each session and made good use of it. I am sure that a lot of developers will jump on the Azure train. Azure is on top of my dev project list after that great event! This platform offers endless opportunities for development and businesses. The cloud environment in general is safer, scales better, and is far more cost effective compared to run and maintain your own data center. Posted: Rainer Habermann

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  • Calculating multiple column average in SQLite3

    - by Benjamin Oakes
    I need to average some values in a row-wise fashion, rather than a column-wise fashion. (If I were doing a column-wise average, I could just use avg()). My specific application of this requires me ignore NULLs in averaging. It's pretty straightforward logic, but seems awfully difficult to do in SQL. Is there an elegant way of doing my calculation? I'm using SQLite3, for what it's worth. Details If you need more details, here's an illustration: I have a a table with a survey: | q1 | q2 | q3 | ... | q144 | |----|-------|-------|-----|------| | 1 | 3 | 7 | ... | 2 | | 4 | 2 | NULL | ... | 1 | | 5 | NULL | 2 | ... | 3 | (Those are just some example values and simple column names. The valid values are 1 through 7 and NULL.) I need to calculate some averages like so: q7 + q33 + q38 + q40 + ... + q119 / 11 as domain_score_1 q10 + q11 + q34 + q35 + ... + q140 / 13 as domain_score_2 ... q2 + q5 + q13 + q25 + ... + q122 / 12 as domain_score_14 ...but i need to pull out the nulls and average based on the non-nulls. So, for domain_score_1 (which has 11 items), I would need to do: Input: 3, 5, NULL, 7, 2, NULL, 3, 1, 5, NULL, 1 (3 + 5 + 7 + 2 + 3 + 1 + 5 + 1) / (11 - 3) 27 / 8 3.375 A simple algorithm I'm considering is: Input: 3, 5, NULL, 7, 2, NULL, 3, 1, 5, NULL, 1 Coalesce each value to 0 if NULL: 3, 5, 0, 7, 2, 0, 3, 1, 5, 0, 1 Sum: 27 Get the number of non-zeros by converting values 0 to 1 and sum: 3, 5, 0, 7, 2, 0, 3, 1, 5, 0, 1 1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1 8 Divide those two numbers 27 / 8 3.375 But that seems like a lot more programming than this should take. Is there an elegant way of doing this that I'm not aware of? Update: Unless I'm misunderstanding something, avg() won't work for this. Example of what I would want to do: select avg(q7, q33, q38, ..., q119) from survey; Output: SQL error near line 3: wrong number of arguments to function avg()

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  • sorting, average and finding the lowest number from a static array Java

    - by user3701322
    i'm trying to input students and input their results for course work and exams and what i'm having trouble with is finding the average total score, the lowest total score and printing all students in order of total scores highest - lowest import java.util.*; import java.text.*; public class Results { static String[] name = new String[100]; static int[] coursework = new int[100]; static int[] exam = new int[100]; static int count = 0; public static void main(String[] args) { Scanner input = new Scanner(System.in); boolean flag = true; while(flag) { System.out.println( "1. Add Student\n" + "2. List All Students\n" + "3. List Student Grades\n" + "4. Total Score Average\n" + "5. Highest Total Score\n" + "6. Lowest Total Score\n" + "7. List all Students and Total Scores\n" + "8. Quit\n"); System.out.print("Enter choice (1 - 8): "); int choice = input.nextInt(); switch(choice) { case 1: add(); break; case 2: listAll(); break; case 3: listGrades(); break; case 4: average(); break; case 5: highestTotal(); break; case 6: lowestTotal(); break; case 7: order(); break; case 8: flag = false; break; default: System.out.println("\nNot an option\n"); } DateFormat dateFormat = new SimpleDateFormat("dd/MM/yyyy HH:mm:ss"); Date date = new Date(); System.out.println(dateFormat.format(date)); } System.out.println("\n\nHave a nice day"); }//end of main static void add() { Scanner input = new Scanner(System.in); System.out.println("Insert Name: "); String names = input.nextLine(); System.out.println("Insert Coursework: "); int courseworks = input.nextInt(); System.out.println("Insert Exam: "); int exams = input.nextInt(); name[count] = names; coursework[count] = courseworks; exam[count] = exams; count++; } static void listAll() { for(int i=0;i<count;i++) { System.out.printf("%s %d %d\n", name[i], coursework[i], exam[i]); } } static void listGrades() { for(int i=0;i<count;i++){ if(coursework[i] + exam[i] > 79) { System.out.println(name[i] + " HD"); } else if(coursework[i] + exam[i] > 69) { System.out.println(name[i] + " DI"); } else if(coursework[i] + exam[i] > 59) { System.out.println(name[i] + " CR"); } else if(coursework[i] + exam[i] > 49) { System.out.println(name[i] + " PA"); } else { System.out.println(name[i] + " NN"); } } } static void average() { } static void highestTotal() { int largest=exam[0]; String student=name[0]; for(int i=0; i<exam.length; i++){ if(exam[i]>largest){ largest = exam[i] + coursework[i]; student = name[i]; } } System.out.printf(student + ": "+ largest + "\n" ); } static void lowestTotal() { int min = 0; for(int i=0; i<=exam[i]; i++){ for(int j =0; j<=exam[i]; j++){ if(exam[i]<=exam[j] && j==exam[j]){ min = exam[i] + coursework[i]; } else{ continue; } } } System.out.printf(name + ": "+ min + "\n" ); } static void order() { } }

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