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• Excel Solver vs Solver Foundation

  - by JoshReuben

  I recently read a book http://www.amazon.com/Scientific-Engineering-Cookbook-Cookbooks-OReilly/dp/0596008791/ref=sr_1_1?ie=UTF8&s=books&qid=1296593374&sr=8-1 - the Excel Scientific and Engineering Cookbook.     The 2 main tools that this book leveraged were the Data Analysis Pack and Excel Solver. I had previously been aquanted with Microsoft Solver Foundation - this is a full fledged API for solving optimization problems, and went beyond being a mere Excel plugin - it exposed a C# programmatic interface for in process and a web service interface for out of process integration. were they the same? apparently not!   2 different solver frameworks for Excel: http://www.solver.com/index.html http://www.solverfoundation.com/ I contacted both vendors to get their perspectives.   Heres what the Excel Solver guys had to say:   "The Solver Foundation requires you to learn and use a very specific modeling language (OML). The Excel solver allows you to formulate your optimization problems without learning any new language simply by entering the formulas into cells on the Excel spreadsheet, something that nearly everyone is already familiar with doing.   The Excel Solver also allows you to seamlessly upgrade to products that combine Monte Carlo Simulation capabilities (our Risk Solver Premium and Risk Solver Platform products) which allow you to include uncertainty into your models when appropriate.   Our advanced Excel Solver Products also have a number of built in reporting tools for advanced analysis of the your model and it's results"           And Heres what the Microsoft Solver Foundation guys had to say:   "  With the release of Solver Foundation 3.0, Solver Foundation has the same kinds of solvers (plus a few more) than what is found in Excel Solver. I think there are two main differences:   1.      Problems are described differently. In Excel Solver the goals and constraints are specified inside the spreadsheet, in formulas. In Solver Foundation they are described either in .Net code that uses the Solver Foundation Services API, or using the OML modeling language in Excel. 2.      Solver Foundation’s primary strength is on solving large linear, mixed integer, and constraint models. That is, models that contain arbitrary nonlinear functions (such as trig functions, IF(), powers, etc) are handled a bit better by the Excel Solver at this point. "

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• Did I lost my RAID again?

  - by BarsMonster

  Hi! A little history: 2 years ago I was really excited to find out that mdadm is so powerful so it even can reshape arrays so you can start with a smaller array and the grow it as you need. I've bought 3x1Tb drives and made RAID-5. It was fine for a year. Then I bought 2x more, and tried to reshape to RAID-6 out of 5 drives, and due to some mess with superblock versions, lost all content. Had to rebuild it from scratch, but 2Tb of data were gone. Yesterday I bought 2 more drives, and this time I had everything: properly built array, UPS. I've disabled write intent map, added 2 new drives as a spare and run a command to grow array to 7-disk. It started working, but speed was ridiculously slow, ~100kb/sec. AFter processing first 37Mb at such an amasing speed, one of old HDDs fails. I properly shutdown PC and disconnected failed drive. After bootup it appeared it recreated intent map as it was still in mdadm config, so I removed it from config and rebooted again. Now all I see is that all mdadm processes deadlocks, and don't do anything. PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 1937 root 20 0 12992 608 444 D 0 0.1 0:00.00 mdadm 2283 root 20 0 12992 852 704 D 0 0.1 0:00.01 mdadm 2287 root 20 0 0 0 0 D 0 0.0 0:00.01 md0_reshape 2288 root 18 -2 12992 820 676 D 0 0.1 0:00.01 mdadm And all I see in mdstat is: $ cat /proc/mdstat Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] md0 : active raid6 sdb1[1] sdg1[4] sdf1[7] sde1[6] sdd1[0] sdc1[5] 2929683456 blocks super 1.2 level 6, 1024k chunk, algorithm 2 [7/6] [UU_UUUU] [>....................] reshape = 0.0% (37888/976561152) finish=567604147.2min speed=0K/sec I've already tried mdadm 2.6.7, 3.1.4 and 3.2 - nothing helps. Did I lost my data again? Any suggestions how can I make it work? OS is Ubuntu Server 10.04.2... PS. Needless to say that data is unaccessible - I cannot mount /dev/md0 as save the most valuable data. You can see my disappointment - the very specific thing I was excited about failed twice taking 5Tb of my data with it.

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• Do I have to worry about "error: superfluous RAID member"?

  - by 0xC0000022L

  When running update-grub on the newly installed Ubuntu 12.04 with an older software RAID (md), I get: error: superfluous RAID member (5 found). error: superfluous RAID member (5 found). Generating grub.cfg ... error: superfluous RAID member (5 found). error: superfluous RAID member (5 found). error: superfluous RAID member (5 found). error: superfluous RAID member (5 found). error: superfluous RAID member (5 found). error: superfluous RAID member (5 found). error: superfluous RAID member (5 found). error: superfluous RAID member (5 found). error: superfluous RAID member (5 found). error: superfluous RAID member (5 found). error: superfluous RAID member (5 found). Found linux image: /boot/vmlinuz-3.2.0-24-generic Found initrd image: /boot/initrd.img-3.2.0-24-generic error: superfluous RAID member (5 found). error: superfluous RAID member (5 found). error: superfluous RAID member (5 found). error: superfluous RAID member (5 found). Found linux image: /boot/vmlinuz-3.2.0-23-generic Found initrd image: /boot/initrd.img-3.2.0-23-generic error: superfluous RAID member (5 found). error: superfluous RAID member (5 found). error: superfluous RAID member (5 found). error: superfluous RAID member (5 found). error: superfluous RAID member (5 found). Found memtest86+ image: /boot/memtest86+.bin error: superfluous RAID member (5 found). error: superfluous RAID member (5 found). error: superfluous RAID member (5 found). error: superfluous RAID member (5 found). error: superfluous RAID member (5 found). Found Debian GNU/Linux (5.0.9) on /dev/sdb1 Found Debian GNU/Linux (5.0.9) on /dev/sdc1 done I would be less worried if the message would say warning: ..., but since it says error: ... I'm wondering what the problem is. # cat /proc/mdstat Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] md2 : active raid1 sdc1[1] sdb1[0] 48829440 blocks [2/2] [UU] md3 : active raid1 sdc2[1] sdb2[0] 263739008 blocks [2/2] [UU] md1 : active raid5 sdg1[3] sdf1[2] sde1[1] sdh1[0] sdi1[4] sdd1[5](S) 1250274304 blocks level 5, 64k chunk, algorithm 2 [5/5] [UUUUU] unused devices: <none> Do I have to worry or is this harmless? btw: disregard the mentioning of Debian 5.0.9, that was the previously installed system and is going to be overwritten. It's on /dev/md2 actually.

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• Desktop Fun: Runic Style Fonts

  - by Asian Angel

  Most of the time regular fonts are just what you need for documents, invitations, or adding text to images. But what if you are in the mood for something unusual or unique to add that perfect touch? If you like older runic style writing, then enjoy finding some new favorites for your collection with our Runic Style Fonts collection. Temple photo by ShinyShiny. Note: To manage the fonts on your Windows 7, Vista, & XP systems see our article here. The Runic Style Fonts Sable Download Worn Manuscript Download JSL Ancient Download Antropos Download Cave Gyrl Download The Roman Runes Alliance Download Ancient Geek Download Troll Download Runish Quill MK *includes two font types Download DS RUNEnglish 2 Download Runes Written *includes two font types Download Wolves And Ravens Download Art Greco Download Dalek Download Glagolitic AOE Download Linear B Download Cartouche Download Greywolf Glyphs *includes 62 individual characters Note: This group represents A – Z in all capital letters. Note: This group represents A – Z in all lower case letters. Note: This group represents the numbers 0 – 9. Download Africain *includes 62 individual characters Note: This group represents A – Z in all capital letters. Note: This group represents A – Z in all lower case letters. Note: This group represents the numbers 0 – 9. Download Cave Writings *includes 52 individual characters Note: This group represents A – Z in all capital letters. Note: This group represents A – Z in all lower case letters. Download For more great ways to customize your computer be certain to look through our Desktop Fun section. Latest Features How-To Geek ETC HTG Projects: How to Create Your Own Custom Papercraft Toy How to Combine Rescue Disks to Create the Ultimate Windows Repair Disk What is Camera Raw, and Why Would a Professional Prefer it to JPG? The How-To Geek Guide to Audio Editing: The Basics How To Boot 10 Different Live CDs From 1 USB Flash Drive The 20 Best How-To Geek Linux Articles of 2010 Five Sleek Audi R8 Car Themes for Chrome and Iron MS Notepad Replacement Metapad Returns with a New Beta Version Spybot Search and Destroy Now Available as a Portable App (PortableApps.com) ShapeShifter: What Are Dreams? [Video] This Computer Runs on Geek Power Wallpaper Bones, Clocks, and Counters; A Look at the First 35,000 Years of Computing

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• CIO's Corner: Achieving a Balance

  - by Michelle Kimihira

  Author: Rick Beers Senior Director, Product Management, Oracle Fusion Middleware All too often, a CIO is unfairly characterized as either technology-focused or business-focused; as more concerned with either infrastructure performance or business excellence. It seems to me that this completely misses the point. I have long thought that a CIO has probably the most complex C-level position in an enterprise, one that requires an artful balance among four entirely different constituencies, often with competing values and needs. How a CIO balances these is the single largest determinant of success. I was reminded of this while reading the excellent interview of Mark Hurd by CNBC’s Maria Bartiromo in a recent issue of USATODAY (Bartiromo: Oracle's Hurd is in tech sweet spot). The interview covers topics such as Big Data, Leadership and Oracle’s growth strategy. But the topic that really got my interest, and reminded me of the need for balance, was on IT spending trends, in which Mark Hurd observed, “…budgets are tight. What most of our customers have today is both an austerity plan to save money and at the same time a plan to reapply that money to innovation. There isn't a customer we have that doesn't have an austerity plan and an innovation plan.” In an era of economic uncertainty, and an accelerating pace of business change, this is probably the toughest balance a CIO must achieve. Yet for far too many IT organizations, operating costs consume over 75% of their budgets, leaving precious little for innovation and investment in business-critical technology programs. I have found that many CIO’s are trapped by their enterprise systems platforms, which were originally architected for Standardization, Compliance and tightly integrated linear Workflows. Yes, these traits are still required for specific reasons and cannot be compromised. But they are no longer enough. New demands are emerging: the explosion in the volume and diversity of Data, the Consumerization of IT, the rise of Social Media, and the need for continual Business Process Reengineering. These were simply not the design criteria for Enterprise 1.0 and attempting to leverage them with current systems platforms results in an escalation in complexity and a resulting increase in operating costs for many IT organizations. This is the cost vs investment trap and what most constrains CIO’s from achieving the balance they need. But there is a way out of this trap. Enterprise 2.0 represents an entirely new enterprise systems architecture, one that is ‘Business-Centric’ rather than ‘ERP Centric’, which defined the architecture of Enterprise 1.0. Oracle’s best in class suite of Fusion Middleware Products enables a layered approach to enterprise systems architectures that provides the balance that an enterprise needs. The most exciting part of all this? The bottom two layers are focused upon reducing costs and the upper two layers provide business value and innovation. Finally, the Balance a CIO needs.  Additional Information Product Information on Oracle.com: Oracle Fusion Middleware Follow us on Twitter and Facebook Subscribe to our regular Fusion Middleware Newsletter

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• Robust line of sight test on the inside of a polygon with tolerance

  - by David Gouveia

  Foreword This is a followup to this question and the main problem I'm trying to solve. My current solution is an hack which involves inflating the polygon, and doing most calculations on the inflated polygon instead. My goal is to remove this step completely, and correctly solve the problem with calculations only. Problem Given a concave polygon and treating all of its edges as if they were walls in a level, determine whether two points A and B are in line of sight of each other, while accounting for some degree of floating point errors. I'm currently basing my solution on a series of line-segment interection tests. In other words: If any of the end points are outside the polygon, they are not in line of sight. If both end points are inside the polygon, and the line segment from A to B crosses any of the edges from the polygon, then they are not in line of sight. If both end points are inside the polygon, and the line segment from A to B does not cross any of the edges from the polygon, then they are in line of sight. But the problem is dealing correctly with all the edge cases. In particular, it must be able to deal with all the situations depicted below, where red lines are examples that should be rejected, and green lines are examples that should be accepted. I probably missed a few other situations, such as when the line segment from A to B is colinear with an edge, but one of the end points is outside the polygon. One point of particular interest is the difference between 1 and 9. In both cases, both end points are vertices of the polygon, and there are no edges being intersected, but 1 should be rejected while 9 should be accepted. How to distinguish these two? I could check some middle point within the segment to see if it falls inside or not, but it's easy to come up with situations in which it would fail. Point 7 was also pretty tricky and I had to to treat it as a special case, which checks if two points are adjacent vertices of the polygon directly. But there are also other chances of line segments being col linear with the edges of the polygon, and I'm still not entirely sure how I should handle those cases. Is there any well known solution to this problem?

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• ssao implementation

  - by Irbis

  I try to implement a ssao based on this tutorial: link I use a deferred rendering and world coordinates for shading calculations. When saving gbuffer a vertex shader output looks like this: worldPosition = vec3(ModelMatrix * vec4(inPosition, 1.0)); normal = normalize(normalModelMatrix * inNormal); gl_Position = ProjectionMatrix * ViewMatrix * ModelMatrix * vec4(inPosition, 1.0); Next for a ssao calculations I render a scene as a full screen quad and I save an occlusion parameter in a texture. (Vertex positions in the world space: link Normals in the world space: link) SSAO implementation: subroutine (RenderPassType) void ssao() { vec2 texCoord = CalcTexCoord(); vec3 worldPos = texture(texture0, texCoord).xyz; vec3 normal = normalize(texture(texture1, texCoord).xyz); vec2 noiseScale = vec2(screenSize.x / 4, screenSize.y / 4); vec3 rvec = texture(texture2, texCoord * noiseScale).xyz; vec3 tangent = normalize(rvec - normal * dot(rvec, normal)); vec3 bitangent = cross(normal, tangent); mat3 tbn = mat3(tangent, bitangent, normal); float occlusion = 0.0; float radius = 4.0; for (int i = 0; i < kernelSize; ++i) { vec3 pix = tbn * kernel[i]; pix = pix * radius + worldPos; vec4 offset = vec4(pix, 1.0); offset = ProjectionMatrix * ViewMatrix * offset; offset.xy /= offset.w; offset.xy = offset.xy * 0.5 + 0.5; float sample_depth = texture(texture0, offset.xy).z; float range_check = abs(worldPos.z - sample_depth) < radius ? 1.0 : 0.0; occlusion += (sample_depth <= pix.z ? 1.0 : 0.0); } outputColor = vec4(occlusion, occlusion, occlusion, 1); } That code gives following results: camera looking towards -z world space: link camera looking towards +z world space: link I wonder if it is possible to use world coordinates in the above code ? When I move camera I get different results because world space positions don't change. Can I treat worldPos.z as a linear depth ? What should I change to get a correct results ? I except the white areas in place of occlusion, so the ground should has the white areas only near to the object.

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• How can I fix my corrupted RAID1 ext4 partition on a Synology DS212 NAS?

  - by Neil

  I have two identical 3 TB disks that were in a RAID1 array, where one disk crashed. I replaced the failed disk, but not after the RAID partitions got messed up. I need to figure out how to restore the RAID array and get at my ext4 partition. Here are the properties of the surviving disk: # fdisk -l /dev/sda fdisk: device has more than 2^32 sectors, can't use all of them Disk /dev/sda: 2199.0 GB, 2199023255040 bytes 255 heads, 63 sectors/track, 267349 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System /dev/sda1 1 267350 2147483647+ ee EFI GPT # parted /dev/sda print Model: ATA ST3000DM001-9YN1 (scsi) Disk /dev/sda: 3001GB Sector size (logical/physical): 512B/512B Partition Table: gpt Disk Flags: Number Start End Size File system Name Flags 1 131kB 2550MB 2550MB ext4 raid 2 2550MB 4698MB 2147MB linux-swap(v1) raid 5 4840MB 3001GB 2996GB raid I replaced the failed drive, and cloned the surviving drive to it so I have something to work with. I cloned the drives with dd if=/dev/sdb of=/dev/sda conv=noerror bs=64M, and now /dev/sda and /dev/sdb are identical. Here is the RAID information: # cat /proc/mdstat Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4] md1 : active raid1 sdb2[1] 2097088 blocks [2/1] [_U] md0 : active raid1 sdb1[1] 2490176 blocks [2/1] [_U] unused devices: <none> It seems that md2 is missing. Here is what testdisk 6.14-WIP finds: Disk /dev/sda - 3000 GB / 2794 GiB - CHS 364801 255 63 Current partition structure: Partition Start End Size in sectors 1 P Linux Raid 256 4980735 4980480 [md0] 2 P Linux Raid 4980736 9175039 4194304 [md1] Invalid RAID superblock 5 P Linux Raid 9453280 5860519007 5851065728 5 P Linux Raid 9453280 5860519007 5851065728 # After a quick search Disk /dev/sda - 3000 GB / 2794 GiB - CHS 364801 255 63 Partition Start End Size in sectors D MS Data 256 4980607 4980352 [1.41.12-2197] D Linux Raid 256 4980735 4980480 [md0] D Linux Swap 4980736 9174895 4194160 D Linux Raid 4980736 9175039 4194304 [md1] >P MS Data 9481056 5858437983 5848956928 [1.41.12-2228] And listing the files on the last partition in the list shows all of my files intact. What should I do?

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• Ubuntu raid 1 write errors

  - by Micah

  I have an Ubuntu server set up with two SATA drives in a RAID 1 configuration with MDADM. The machine is used to record raw video, which involves a lot of writing to the disk. Sometimes during video recording the computer will crash, will the following errors in kern.log: Mar 15 10:39:41 video kernel: [414501.629864] ata2.00: exception Emask 0x10 SAct 0x0 SErr 0x400100 action 0x6 Mar 15 10:39:41 video kernel: [414501.629870] ata2.00: BMDMA stat 0x26 Mar 15 10:39:41 video kernel: [414501.629875] ata2.00: SError: { UnrecovData Handshk } Mar 15 10:39:41 video kernel: [414501.629880] ata2.00: failed command: WRITE DMA EXT Mar 15 10:39:41 video kernel: [414501.629889] ata2.00: cmd 35/00:00:28:6d:f6/00:04:06:00:00/e0 tag 0 dma 524288 out Mar 15 10:39:41 video kernel: [414501.629891] res 51/84:b1:77:6e:f6/84:02:06:00:00/e0 Emask 0x30 (host bus error) Mar 15 10:39:41 video kernel: [414501.629896] ata2.00: status: { DRDY ERR } Mar 15 10:39:41 video kernel: [414501.629899] ata2.00: error: { ICRC ABRT } Mar 15 10:39:41 video kernel: [414501.629910] ata2.00: hard resetting link Mar 15 10:39:41 video kernel: [414501.973009] ata2.01: hard resetting link Mar 15 10:39:41 video kernel: [414502.482642] ata2.00: SATA link up 3.0 Gbps (SStatus 123 SControl 300) Mar 15 10:39:41 video kernel: [414502.482658] ata2.01: SATA link down (SStatus 0 SControl 300) Mar 15 10:39:41 video kernel: [414502.546160] ata2.00: configured for UDMA/133 Mar 15 10:39:41 video kernel: [414502.546203] ata2: EH complete Is this the result of faulty drives? Is software RAID just not performant enough for data rates ~15 MB/s, even with a quad-core i7? Thanks for your help. Edit: cat /proc/mdstat returns this: Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] md0 : active raid1 sdb1[1] sda1[0] 976760768 blocks [2/2] [UU] unused devices: <none>

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• Request Tracker 4: Ticket Escalation

  - by Randy

  I am running Request Tracker 4 on a Debian Squeeze Server. I have to implement a priority escalation. Actually escalation is not the right term for this since the the ticket priority should be set linear via rt-crontool (or any other tool that can be run via a cronjob) dependent on the time that has been passed between the „Started“ and „Due“ to a number between 0 (starting priority) and the „Final Priority“ (eg. 100) while the value of the „Final Priority“ should be reached exactly the moment the „Due“-Date is passed. This already implies that the search condition should be all tickets of a certain queue that have „Started“ AND „Due“ AND „Final Priority“. The cronjob should be called very frequently for excample any 5 or 10 minutes so that the call should be indempotent and not depentent on the frequency of the rt-crontool invocations. One Example: A Ticket is Started at 2012-12-23 0am and Due is 2012-12-23 11.59pm while the Final Priority is 100. When the call is made at noon the priority should be set to 50. Could anybody help me with this? Thank you for reading this to the bottom!

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• Going from a math career to a cs career: how to do it?

  - by Joseph

  Hey, I'm looking for some advice on how to successfully make the transition from mathematics to CS. My academic background is in mathematics (BS and MSc), and I've taken loads of math courses as well. You name it, and I took it: Measure Theory, Algebra, PDES, Manifolds, Complex Analysis, etc. I progressed quite far along this track, and at one point, I thought I would be a professional mathematician...But around the time I was finishing my MSc, I really got sick of it. Studying very abstract mathematics was fun, but it really lost it's appeal to me. Outside of a couple hundred people, I'm not sure if anybody would understand my research. I did not want to be 60 years old and say that my only contribution to the world consisted of published papers. Anyways, I've been an off and on hobbyist programmer since 2002. I've programmed in C and Java (just small projects), and I really started to be drawn to the area as time passed. There's a real appeal to CS work because, well, it actually means something to other people out there! I enjoy all parts of it: designing webpages (a real artistic appeal). On the other end, I do enjoy toying with compilers and more nitty-gritty stuff as well. Suffice to say, I have broad interests out there. Anyways, I know it's a bit late, but I was wondering if there were other folks out there who made the change, and if so, how I could do so. I know I have some fairly big gaps to fill in terms of data structures, lack of internship experience, etc. But I really would like to make this work. So my question is simply: How can I make the switch from math to CS? To pay the bills, I'll be doing financial analysis for a company, but I'd like to eventually transition into a developer type position. I've been reading "Algorithm Design" by Tardos and doing all the problems. It's not hard to make progress since the problems are far more concrete than the stuff I've been doing the past six years. I feel I can make fairly rapid progress in picking up all the materials from data structures, etc. but none of it can substitute the past several years I've lost. Anyways, I'm eager to learn but would love some advice/concrete direction. Thanks, Joseph

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• Will these optimizations to my Ruby implementation of diff improve performance in a Rails app?

  - by grg-n-sox

  <tl;dr> In source version control diff patch generation, would it be worth it to use the optimizations listed at the very bottom of this writing (see <optimizations>) in my Ruby implementation of diff for making diff patches? </tl;dr> <introduction> I am programming something I have never done before and there might already be tools out there to do the exact thing I am programming but at this point I am having too much fun to care so I am still going to do it from scratch, even if there is a tool for this. So anyways, I am working on a Ruby on Rails app and need a certain feature. Basically I want each entry in a table of mine, let's say for example a table of video games, to have a stored chunk of text that represents a review or something of the sort for that table entry. However, I want this text to be both editable by any registered user and also keep track of different submissions in a version control system. The simplest solution I could think of is just implement a solution that keeps track of the text body and the diff patch history of different versions of the text body as objects in Ruby and then serialize it, preferably in human readable form (so I'll most likely use YAML for this) for editing if needed due to corruption by a software bug or a mistake is made by an admin doing some version editing. So at first I just tried to dive in head first into this feature to find that the problem of generating a diff patch is more difficult that I thought to do efficiently. So I did some research and came across some ideas. Some I have implemented already and some I have not. However, it all pretty much revolves around the longest common subsequence problem, as you would already know if you have already done anything with diff or diff-like features, and optimization the function that solves it. Currently I have it so it truncates the compared versions of the text body from the beginning and end until non-matching lines are found. Then it solves the problem using a comparison matrix, but instead of incrementing the value stored in a cell when it finds a matching line like in most longest common subsequence algorithms I have seen examples of, I increment when I have a non-matching line so as to calculate edit distance instead of longest common subsequence. Although as far as I can tell between the two approaches, they are essentially two sides of the same coin so either could be used to derive an answer. It then back-traces through the comparison matrix and notes when there was an incrementation and in which adjacent cell (West, Northwest, or North) to determine that line's diff entry and assumes all other lines to be unchanged. Normally I would leave it at that, but since this is going into a Rails environment and not just some stand-alone Ruby script, I started getting worried about needing to optimize at least enough so if a spammer that somehow knew how I implemented the version control system and knew my worst case scenario entry still wouldn't be able to hit the server that bad. After some searching and reading of research papers and articles through the internet, I've come across several that seem decent but all seem to have pros and cons and I am having a hard time deciding how well in this situation that the pros and cons balance out. So are the ones listed here worth it? I have listed them with known pros and cons. </introduction> <optimizations> Chop the compared sequences into multiple chucks of subsequences by splitting where lines are unchanged, and then truncating each section of unchanged lines at the beginning and end of each section. Then solve the edit distance of each subsequence. Pro: Changes the time increase as the changed area gets bigger from a quadratic increase to something more similar to a linear increase. Con: Figuring out where to split already seems like you have to solve edit distance except now you don't care how it is changed. Would be fine if this was solvable by a process closer to solving hamming distance but a single insertion would throw this off. Use a cryptographic hash function to both convert all sequence elements into integers and ensure uniqueness. Then solve the edit distance comparing the hash integers instead of the sequence elements themselves. Pro: The operation of comparing two integers is faster than the operation of comparing two strings, so a slight performance gain is received after every comparison, which can be a lot overall. Con: Using a cryptographic hash function takes time to convert all the sequence elements and may end up costing more time to do the conversion that you gain back from the integer comparisons. You could use the built in hash function for a string but that will not guarantee uniqueness. Use lazy evaluation to only calculate the three center-most diagonals of the comparison matrix and then only calculate additional diagonals as needed. And then also use this approach to possibly remove the need on some comparisons to compare all three adjacent cells as desribed here. Pro: Can turn an algorithm that always takes O(n * m) time and make it so only worst case scenario is that time, best case becomes practically linear, and average case is somewhere between the two. Con: It is an algorithm I've only seen implemented in functional programming languages and I am having a difficult time comprehending how to convert this into Ruby based on how it is described at the site linked to above. Make a C module and do the hard work at the native level in C and just make a Ruby wrapper for it so Ruby can make all the calls to it that it needs. Pro: I have to imagine that evaluating something like this in could be a LOT faster. Con: I have no idea how Rails handles apps with ruby code that has C extensions and it hurts the portability of the app. This is an optimization for after the solving of edit distance, but idea is to store additional combined diffs with the ones produced by each version to make a delta-tree data structure with the most recently made diff as the root node of the tree so getting to any version takes worst case time of O(log n) instead of O(n). Pro: Would make going back to an old version a lot faster. Con: It would mean every new commit, the delta-tree would get a new root node that will cost time to reorganize the delta-tree for an operation that will be carried out a lot more often than going back a version, not to mention the unlikelihood it will be an old version. </optimizations> So are these things worth the effort?

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• Degraded RAID-5 array with lvm2 lost superblock and partition table

  - by Fred Phillips

  I have a RAID-5 array of 4x1TB hard disks with one lvm2 partition on Ubuntu Linux 10.04 LTS. One of the disks has failed. I have re-assembled the array without this failed disk but now mdadm --examine claims the array has no superblock and fdisk says it has no partition table. What can I do to recover the data? # mdadm -D /dev/md0 /dev/md0: Version : 1.2 Creation Time : Sat Mar 5 14:43:49 2011 Raid Level : raid5 Array Size : 2930276352 (2794.53 GiB 3000.60 GB) Used Dev Size : 976758784 (931.51 GiB 1000.20 GB) Raid Devices : 4 Total Devices : 4 Persistence : Superblock is persistent Update Time : Sat Mar 5 15:06:49 2011 State : clean, degraded Active Devices : 3 Working Devices : 3 Failed Devices : 1 Spare Devices : 0 Layout : left-symmetric Chunk Size : 512K Name : boba:1 (local to host boba) UUID : 52eb4bc9:c3d8aab5:e0699505:e0e1aa05 Events : 18 Number Major Minor RaidDevice State 0 8 1 0 active sync /dev/sda1 1 8 65 1 active sync /dev/sde1 2 8 49 2 active sync /dev/sdd1 3 0 0 3 removed 4 8 17 - faulty spare /dev/sdb1 # mdadm --examine /dev/md0 mdadm: No md superblock detected on /dev/md0. # fdisk -l /dev/md0 Disk /dev/md0: 3000.6 GB, 3000602984448 bytes 2 heads, 4 sectors/track, 732569088 cylinders Units = cylinders of 8 * 512 = 4096 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 524288 bytes / 1572864 bytes Disk identifier: 0x00000000 Disk /dev/md0 doesn't contain a valid partition table # cat /proc/mdstat Personalities : [raid6] [raid5] [raid4] [linear] [multipath] [raid0] [raid1] [raid10] md0 : active raid5 sdb1[4](F) sda1[0] sdd1[2] sde1[1] 2930276352 blocks super 1.2 level 5, 512k chunk, algorithm 2 [4/3] [UUU_] unused devices: <none>

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• How do we, as a community, help encourage programming in public schools? (Or state Schools for the U

  - by NoMoreZealots

  PRIMARY MOTIVATION My office gets involved with the "First Robotics" competitions and one thing that lingers year to year is the students typically have no preparation for doing even simple programming as part of the public schools system. While the science classes provide some basic grasp of mechanical and electrical concepts, by in large computer programming gets no coverage from the curriculum. (This my be different in other areas of the country/world.) What makes it worse is there is only a short period of time you have to prepare the student's and help them design the robot. Talking to some professors from local colleges, it's a problem because you can't assume even the most basic understanding for freshman CS majors. Languages like Python, Lua and BASIC are simple enough for at least high school level students, if not younger. SCOPE So how do you get public schools to support a programming, at least to the level of "Try it in BASIC" examples that used to be at the end of a chapter in my Algebra book? At least enough to prepare them for event's such as the FIRST Robotic competitions. Which the primary objectives are to teach problem solving and team work, and to possible foster an interest in Math, Science and Engineering in general. (Not force feed to them, as some people her seem to be implying.) Edit: Why teach kids: (Since 2000 CS enrollment in US colleges has decreased by 70% while college enrollment has increased, this is a PROBLEM.) Saying there is no value in teaching someone programming in Jr./High school because they might think "they know programming." Is like saying there's no value in teaching High school science and physics, because they might decide they "know physics." Leading to abuse like: "I passed a high school physics class, I'm going to develop a Unified Quantum Gravitational Theory." Better Prepared students are better students. Instead it would allows college programs to raise the bar on the entry level courses, allowing students to be weeded out based on their understanding of more advanced material. Plus people who did poorly in that in topic in High school aren't as likely to say "I think there's money in computer's so I'll computer science." Plus if people take it in high school and decide THEN that it's not for them, it's better than them wasting their money to PAY a college to figure that out. The result is that people who take the degree are more likely to succeed and be there for the RIGHT reasons. (i.e. It's what they REALLY want to do. And that's REALLY the key to being good at anything.) Programming is like anything else, the more practice and genuine interest you have the better you get. If you start them later, they get less practice. The earlier give them the opportunity to start, the more practice they will get. All other things equal, the more practice the better the programmer.

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• Finding custom printer-specific options on *nix

  - by enbuyukfener

  Hey all, I have a printer set up using CUPS (FujiXerox Document Center 1100), it is named DC1100. There are capabilities of the printer that are not shows as options of the printer as listed by: lpoptions -l -d DC1100 The output is below: PrintoutMode/Printout Mode: Draft *Normal High Photo InputSlot/Media Source: Upper Lower MultiPurpose LargeCapacity Manual *Standard PageSize/Page Size: *Letter A4 C5 C6 COM10 DL Executive Legal Monarch Statement PageRegion/PageRegion: Letter A4 C5 C6 COM10 DL Executive Legal Monarch Statement STP_Brightness/Brightness: 0.00 0.02 0.04 [snip] 2.00 STP_Contrast/Contrast: 0.00 0.05 0.10 0.15 [snip] 4.00 STP_ColorCorrection/Color Correction: Accurate Bright Density [snip] Uncorrected STP_DitherAlgorithm/Dither Algorithm: Adaptive EvenTone Fast [snip] VeryFast STP_EnableDensity/Density Enable: *Disabled Enabled STP_Density/Density Value: 0.1 0.2 0.3 0.4 [snip] 8.0 STP_EnableGamma/Composite Gamma Enable: *Disabled Enabled STP_Gamma/Composite Gamma Value: 0.10 0.15 0.20 0.25 [snip] 4.00 STP_LinearContrast/Linear Contrast Adjustment: *False True STP_Duplex/Double-Sided Printing: DuplexNoTumble DuplexTumble *None Resolution/Rendering Resolution: *FromPrintoutMode 150x150dpi 300x300dpi 600x600dpi OutputType/Output Type: *FromPrintoutMode BlackAndWhite Grayscale STP_ImageType/Image Type: *FromPrintoutMode Photo Graphics LineArt None Text TextGraphics STP_Resolution/Resolution: *FromPrintoutMode 150dpi 300dpi 600dpi I am particularly looking for options for: "secure print" (possibly by setting a mode and setting a username) stapling hole punching Perhaps I need a vendor specific driver/PPD file? If so, any pointers as I have no idea where to look for one. I haven't been able to find one on the official site or on sites such as http://www.openprinting.org

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• How to get an inactive RAID device working again?

  - by Jonik

  After booting, my RAID1 device (/dev/md_d0 *) sometimes goes in some funny state and I cannot mount it. * Originally I created /dev/md0 but it has somehow changed itself into /dev/md_d0. # mount /opt mount: wrong fs type, bad option, bad superblock on /dev/md_d0, missing codepage or helper program, or other error (could this be the IDE device where you in fact use ide-scsi so that sr0 or sda or so is needed?) In some cases useful info is found in syslog - try dmesg | tail or so The RAID device appears to be inactive somehow: # cat /proc/mdstat Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] md_d0 : inactive sda4[0](S) 241095104 blocks # mdadm --detail /dev/md_d0 mdadm: md device /dev/md_d0 does not appear to be active. Question is, how to make active the device again (using mdmadm, I presume)? (Other times it's alright (active) after boot, and I can mount it manually without problems. But it still won't mount automatically even though I have it in /etc/fstab: /dev/md_d0 /opt ext4 defaults 0 0 So a bonus question: what should I do to make the RAID device automatically mount at /opt at boot time?) This is an Ubuntu 9.10 workstation. Background info about my RAID setup in this question.

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• How to play 24 fps video smoothly on a 60Hz display?

  - by netvope

  I use mpc-hc to play videos on Win7 x64. With the default settings (#1), video playback is great most of the time. But for panning shots, playback is not smooth. I stepped through the video frame by frame and found that the panning movement is smooth (e.g. each frame shifts horizontally by 10 pixels), so the problem is how the 23.976 fps video is interpolated to 60Hz. The judder looks like what would be caused by a "2:3 pulldown", where the frames are played unevenly like: frame 1, 1, 2, 2, 2, 3, 3, 4, 4, 4, etc (#2) Using "optimal renderer settings" (#3) instead of the default disables the Aero theme and causes tearing. Setting my LCD display to 50Hz may have improved the judder slightly (but I can't really tell). My display does not support 24Hz or 48Hz, and forcing them in the Nvidia control panel gives blurry screen. I've tried other video players (VLC and KMPlayer), the ReClock Directshow Filter, video files from different sources (#4), turning on/off DXVA, and a computer with a different GPU, but the judder in the playback is similar. None of them solved the problem. So, how can I play 23.976 or 24 fps video smoothly on a 60Hz display? I think a video player could make the video smoother by doing linear interpolation, such as: 1. 100% frame 1 2. 60% frame 1 + 40% frame 2 3. 20% frame 1 + 80% frame 2 4. 80% frame 2 + 20% frame 3 5. 40% frame 2 + 60% frame 3 6. 100% frame 3 7. 60% frame 3 + 40% frame 4 .. etc Can any existing video player do this? Footnotes: (#1) Video renderer: EVR Custom Pres. (#2) This example converts a 24 fps video into 30 fps (#3) View Renderer settings Reset Reset to optimal renderer settings (#4) The files I have are all H.264 mkv files, but I don't think the file format/encoding matters.

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• How to re-add a RAID-10 failed drive on Ubuntu?

  - by thiesdiggity

  I have a problem that I can't seem to solve. We have a Ubuntu server setup with RAID-10 and two of the drives dropped out of the array. When I try to re-add them using the following command: mdadm --manage --re-add /dev/md2 /dev/sdc1 I get the following error message: mdadm: Cannot open /dev/sdc1: Device or resource busy When I do a "cat /proc/mdstat" I get the following: Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [r$ md2 : active raid10 sdb1[0] sdd1[3] 1953519872 blocks 64K chunks 2 near-copies [4/2] [U__U] md1 : active raid1 sda2[0] sdc2[1] 468853696 blocks [2/2] [UU] md0 : active raid1 sda1[0] sdc1[1] 19530688 blocks [2/2] [UU] unused devices: <none> When I run "/sbin/mdadm --detail /dev/md2" I get the following: /dev/md2: Version : 00.90 Creation Time : Mon Sep 5 23:41:13 2011 Raid Level : raid10 Array Size : 1953519872 (1863.02 GiB 2000.40 GB) Used Dev Size : 976759936 (931.51 GiB 1000.20 GB) Raid Devices : 4 Total Devices : 2 Preferred Minor : 2 Persistence : Superblock is persistent Update Time : Thu Oct 25 09:25:08 2012 State : active, degraded Active Devices : 2 Working Devices : 2 Failed Devices : 0 Spare Devices : 0 Layout : near=2, far=1 Chunk Size : 64K UUID : c6d87d27:aeefcb2e:d4453e2e:0b7266cb Events : 0.6688691 Number Major Minor RaidDevice State 0 8 17 0 active sync /dev/sdb1 1 0 0 1 removed 2 0 0 2 removed 3 8 49 3 active sync /dev/sdd1 Output of df -h is: Filesystem Size Used Avail Use% Mounted on /dev/md1 441G 2.0G 416G 1% / none 32G 236K 32G 1% /dev tmpfs 32G 0 32G 0% /dev/shm none 32G 112K 32G 1% /var/run none 32G 0 32G 0% /var/lock none 32G 0 32G 0% /lib/init/rw tmpfs 64G 215M 63G 1% /mnt/vmware none 441G 2.0G 416G 1% /var/lib/ureadahead/debugfs /dev/mapper/RAID10VG-RAID10LV 1.8T 139G 1.6T 8% /mnt/RAID10 When I do a "fdisk -l" I can see all the drives needed for the RAID-10. The RAID-10 is part of the /dev/mapper, could that be the reason why the device is coming back as busy? Anyone have any suggestions on what I can try to get the drives back into the array? Any help would be greatly appreciated. Thanks!

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• memory tuning with rails/unicorn running on ubuntu

  - by user970193

  I am running unicorn on Ubuntu 11, Rails 3.0, and Ruby 1.8.7. It is an 8 core ec2 box, and I am running 15 workers. CPU never seems to get pinned, and I seem to be handling requests pretty nicely. My question concerns memory usage, and what concerns I should have with what I am seeing. (if any) Here is the scenario: Under constant load (about 15 reqs/sec coming in from nginx), over the course of an hour, each server in the 3 server cluster loses about 100MB / hour. This is a linear slope for about 6 hours, then it appears to level out, but still maybe appear to lose about 10MB/hour. If I drop my page caches using the linux command echo 1 /proc/sys/vm/drop_caches, the available free memory shoots back up to what it was when I started the unicorns, and the memory loss pattern begins again over the hours. Before: total used free shared buffers cached Mem: 7130244 5005376 2124868 0 113628 422856 -/+ buffers/cache: 4468892 2661352 Swap: 33554428 0 33554428 After: total used free shared buffers cached Mem: 7130244 4467144 2663100 0 228 11172 -/+ buffers/cache: 4455744 2674500 Swap: 33554428 0 33554428 My Ruby code does use memoizations and I'm assuming Ruby/Rails/Unicorn is keeping its own caches... what I'm wondering is should I be worried about this behaviour? FWIW, my Unicorn config: worker_processes 15 listen "#{CAPISTRANO_ROOT}/shared/pids/unicorn_socket", :backlog = 1024 listen 8080, :tcp_nopush = true timeout 180 pid "#{CAPISTRANO_ROOT}/shared/pids/unicorn.pid" GC.respond_to?(:copy_on_write_friendly=) and GC.copy_on_write_friendly = true before_fork do |server, worker| STDERR.puts "XXXXXXXXXXXXXXXXXXX BEFORE FORK" print_gemfile_location defined?(ActiveRecord::Base) and ActiveRecord::Base.connection.disconnect! defined?(Resque) and Resque.redis.client.disconnect old_pid = "#{CAPISTRANO_ROOT}/shared/pids/unicorn.pid.oldbin" if File.exists?(old_pid) && server.pid != old_pid begin Process.kill("QUIT", File.read(old_pid).to_i) rescue Errno::ENOENT, Errno::ESRCH # already killed end end File.open("#{CAPISTRANO_ROOT}/shared/pids/unicorn.pid.ok", "w"){|f| f.print($$.to_s)} end after_fork do |server, worker| defined?(ActiveRecord::Base) and ActiveRecord::Base.establish_connection defined?(Resque) and Resque.redis.client.connect end Is there a need to experiment enforcing more stringent garbage collection using OobGC (http://unicorn.bogomips.org/Unicorn/OobGC.html)? Or is this just normal behaviour, and when/as the system needs more memory, it will empty the caches by itself, without me manually running that cache command? Basically, is this normal, expected behaviour? tia

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• How do I reinitialise a failed RAID 5 drive using terminal on Ubuntu Server

  - by Stephen

  I've currently put together a new system and part of that has been creating a software RAID 5 using 'mdadm' in Ubuntu Server. I successfully got to the point where I create the array using: sudo mdadm --create --verbose /dev/md0 --level=5 --raid-devices=4 /dev/sda1 /dev/sdb1 /dev/sdc1 /dev/sdd1 I left it to do its thing overnight then used the following command to check on it: watch cat /proc/mdstat To which the following was returned: Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] md0 : active raid5 sdd1[4](S) sdc1[2] sdb1[1] sda1[0](F) 5860535808 blocks super 1.2 level 5, 512k chunk, algorithm 2 [4/2] [_UU_] unused devices: <none> It appears that one has failed (and I'm not too savvy with why another is a spare). So, just to be sure that something else isn't amiss I wanted to try and re-engage the failed drive. Can someone explain how I can do that and what I should do with the spare (if anything). And also how do I know when synchronisation is complete? The tutorial I used to get this far is located here: http://sonniesedge.co.uk/2009/06/13/software-raid-5-on-ubuntu-904/ Many thanks! p.s. Here is some extra information that may help: sudo mdadm --detail /dev/md0 /dev/md0: Version : 1.2 Creation Time : Mon Jun 18 21:14:21 2012 Raid Level : raid5 Array Size : 5860535808 (5589.04 GiB 6001.19 GB) Used Dev Size : 1953511936 (1863.01 GiB 2000.40 GB) Raid Devices : 4 Total Devices : 4 Persistence : Superblock is persistent Update Time : Mon Jun 18 21:50:26 2012 State : clean, FAILED Active Devices : 2 Working Devices : 3 Failed Devices : 1 Spare Devices : 1 Layout : left-symmetric Chunk Size : 512K Name : myraidbox:0 (local to host myraidbox) UUID : a269ee94:a161600c:fb1665e7:bd2f27b3 Events : 13 Number Major Minor RaidDevice State 0 0 0 0 removed 1 8 17 1 active sync /dev/sdb1 2 8 33 2 active sync /dev/sdc1 3 0 0 3 removed 0 8 1 - faulty spare /dev/sda1 4 8 49 - spare /dev/sdd1

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• Failing to load rootfs: Ubuntu 10 + grub2 + rootfs ext4 w/ RAID1

  - by James

  I am having problems booting a new Ubuntu 10 (server) install. My primary HD (/dev/sda) is laid out as follows: Device Boot Start End Blocks Id System /dev/sda1 * 1 18 144553+ 83 Linux <-- /BOOT /dev/sda2 19 182401 1464991447+ 5 Extended /dev/sda5 19 2207 17583111 fd Linux raid autodetect /dev/sda6 2208 11934 78132096 fd Linux raid autodetect <-- / (ROOTFS) /dev/sda7 11935 182401 1369276146 fd Linux raid autodetect The rootfs is part of a RAID1 (software) array (currently degraded): # cat /proc/mdstat Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] md2 : active raid1 sda6[1] 78132032 blocks [2/1] [_U] The UUIDs for the partitions are as follows: # blkid /dev/sda1 /dev/sda1: UUID="b25dd301-41b9-4f4d-9b0a-0e31713dd74c" TYPE="ext2" # blkid /dev/sda6 /dev/sda6: UUID="af7b9ede-fa53-c0c1-74be-31ec752c5cd5" TYPE="linux_raid_member" # blkid /dev/md2 /dev/md2: UUID="a0602d42-6855-482f-870c-6f6ecdcdae3f" TYPE="ext4" Finally, I have my grub2 menuentry setup as follows: ### BEGIN /etc/grub.d/10_linux ### menuentry 'Ubuntu, with Linux 2.6.32-25-server' --class ubuntu --class gnu-linux --class gnu --class os { insmod ext2 insmod raid insmod mdraid set root='(hd0,1)' search --no-floppy --fs-uuid --set b25dd301-41b9-4f4d-9b0a-0e31713dd74c linux /vmlinuz-2.6.32-25-server root=UUID=a0602d42-6855-482f-870c-6f6ecdcdae3f ro nosplash noplymouth initrd /initrd.img-2.6.32-25-server } When I attempt to boot, grub loads OK, however I eventually get the following error message: Gave up waiting for root device. ALERT /dev/disk/by-uuid/a0602d42-6855-482f-870c-6f6ecdcdae3f does not exist. Dropping to a shell! If from the grub bootloader I open a grub command line, I can ls (hd0,) and it lists the correct partitions with the UUIDs as shown above - sda6 shows 'a0602d42-6855-482f-870c-6f6ecdcdae3f' (the RAID UUID). If I ls (md2)/ it properly lists all the files on the RAID1 filesystem (ext4) so it doesn't appear to be an issue accessing the raid device. Does anyone have any suggestions as to what the problem might be? I can't figure this one out.

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• Excel or OpenOffice Table Summary: how to reconstruct a table from another, with "missing" values

  - by Gilberto

  I have a table of values (partial) with 3 columns: month (from 1 to 12), code and value. E.g., MONTH | CODE | VALUE 1 | aaa | 111 1 | bbb | 222 1 | ccc | 333 2 | aaa | 1111 2 | ccc | 2222 The codes are clients and the values are sales volumes. Each row represents the sales for one month for one client. So I have three clients, namely aaa, bbb, and ccc. For month=1 their sales volumes are: aaa-111, bbb-222, and ccc-333. A client may or may not have sales for every month; for example, for the month 2, the client bbb has no sales. I have to construct a completed summary table for all the MONTH / CODE pairs with their corresponding VALUE (using the value from the "partial" table, if present, otherwise print a string "missing"). MONTH | CODE | VALUE 1 | aaa | 111 1 | bbb | 222 1 | ccc | 333 2 | aaa | 1111 2 | bbb | missing 2 | ccc | 2222 Or, to put it another way, the table is a linear representation of a matrix:                                 and I want to identify the cells for which no value was provided. How can I do that?

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• How to force mdadm to stop RAID5 array?

  - by lucek

  I have /dev/md127 RAID5 array that consisted of four drives. I managed to hot remove them from the array and currently /dev/md127 does not have any drives: cat /proc/mdstat Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] md0 : active raid1 sdd1[0] sda1[1] 304052032 blocks super 1.2 [2/2] [UU] md1 : active raid0 sda5[1] sdd5[0] 16770048 blocks super 1.2 512k chunks md127 : active raid5 super 1.2 level 5, 512k chunk, algorithm 2 [4/0] [____] unused devices: <none> and mdadm --detail /dev/md127 /dev/md127: Version : 1.2 Creation Time : Thu Sep 6 10:39:57 2012 Raid Level : raid5 Array Size : 8790402048 (8383.18 GiB 9001.37 GB) Used Dev Size : 2930134016 (2794.39 GiB 3000.46 GB) Raid Devices : 4 Total Devices : 0 Persistence : Superblock is persistent Update Time : Fri Sep 7 17:19:47 2012 State : clean, FAILED Active Devices : 0 Working Devices : 0 Failed Devices : 0 Spare Devices : 0 Layout : left-symmetric Chunk Size : 512K Number Major Minor RaidDevice State 0 0 0 0 removed 1 0 0 1 removed 2 0 0 2 removed 3 0 0 3 removed I've tried to do mdadm --stop /dev/md127 but: mdadm --stop /dev/md127 mdadm: Cannot get exclusive access to /dev/md127:Perhaps a running process, mounted filesystem or active volume group? I made sure that it's unmounted, umount -l /dev/md127 and confirmed that it indeed is unmounted: umount /dev/md127 umount: /dev/md127: not mounted I've tried to zero superblock of each drive and I get (for each drive): mdadm --zero-superblock /dev/sde1 mdadm: Unrecognised md component device - /dev/sde1 Here's output of lsof|grep md127: lsof|grep md127 md127_rai 276 root cwd DIR 9,0 4096 2 / md127_rai 276 root rtd DIR 9,0 4096 2 / md127_rai 276 root txt unknown /proc/276/exe What else can I do? LVM is not even installed so it can't be a factor.

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• How to play 24 fps video smoothly on a 60Hz display? (or which player supports frame interpolation?)

  - by netvope

  I use mpc-hc to play videos on Win7 x64. With the default settings (#1), video playback is great most of the time. But for panning shots, playback is not smooth. I stepped through the video frame by frame and found that the panning movement is smooth (e.g. each frame shifts horizontally by 10 pixels), so the problem is how the 23.976 fps video is interpolated to 60Hz. The judder looks like what would be caused by a "2:3 pulldown", where the frames are played unevenly like: frame 1, 1, 2, 2, 2, 3, 3, 4, 4, 4, etc (#2) Using "optimal renderer settings" (#3) instead of the default disables the Aero theme and causes tearing. Setting my LCD display to 50Hz may have improved the judder slightly (but I can't really tell). My display does not support 24Hz or 48Hz, and forcing them in the Nvidia control panel gives blurry screen. I've tried other video players (VLC and KMPlayer), the ReClock Directshow Filter, video files from different sources (#4), turning on/off DXVA, and a computer with a different GPU, but the judder in the playback is similar. None of them solved the problem. So, how can I play 23.976 or 24 fps video smoothly on a 60Hz display? I think a video player could make the video smoother by doing linear interpolation, such as: 1. 100% frame 1 2. 60% frame 1 + 40% frame 2 3. 20% frame 1 + 80% frame 2 4. 80% frame 2 + 20% frame 3 5. 40% frame 2 + 60% frame 3 6. 100% frame 3 7. 60% frame 3 + 40% frame 4 .. etc Can any existing video player do this? Footnotes: (#1) Video renderer: EVR Custom Pres. (#2) This example converts a 24 fps video into 30 fps (#3) View Renderer settings Reset Reset to optimal renderer settings (#4) The files I have are all H.264 mkv files, but I don't think the file format/encoding matters.

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• How to minimize the risk of employees spreading critical information?

  - by Industrial

  Hi everyone, What's common sense when it comes to minimising the risk of employees spreading critical information to rivalling companies? As of today, it's clear that not even the US government and military can be sure that their data stays safely within their doors. Thereby I understand that my question probably instead should be written as "What is common sense to make it harder for employees to spread business critical information?" If anyone would want to spread information, they will find a way. That's the way life work and always has. If we make the scenario a bit more realistic by narrowing our workforce by assuming we only have regular John Does onboard and not Linux-loving sysadmins , what should be good precautions to at least make it harder for the employees to send business-critical information to the competition? As far as I can tell, there's a few obvious solutions that clearly has both pros and cons: Block services such as Dropbox and similar, preventing anyone to send gigabytes of data through the wire. Ensure that only files below a set size can be sent as email (?) Setup VLANs between departments to make it harder for kleptomaniacs and curious people to snoop around. Plug all removable media units - CD/DVD, Floppy drives and USB Make sure that no configurations to hardware can be made (?) Monitor network traffic for non-linear events (how?) What is realistic to do in a real world? How does big companies handle this? Sure, we can take the former employer to court and sue, but by then the damage has already been caused... Thanks a lot

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