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• Dynamic memory allocation for 3D array

  - by javierkeung

  How can i allocate 3D arrays using malloc?

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• Is sstable2json broken in Cassandra 0.6.0-beta3?

  - by knorv

  I'm getting NullPointerException:s when using sstable2json in Cassandra 0.6.0-beta3: $ bin/sstable2json .../cassandra/data/system/LocationInfo-1-Data.db Exception in thread "main" java.lang.NullPointerException at java.util.Arrays$ArrayList.<init>(Arrays.java:3357) at java.util.Arrays.asList(Arrays.java:3343) at org.apache.cassandra.tools.SSTableExport.export(SSTableExport.java:255) at org.apache.cassandra.tools.SSTableExport.export(SSTableExport.java:299) at org.apache.cassandra.tools.SSTableExport.export(SSTableExport.java:323) at org.apache.cassandra.tools.SSTableExport.main(SSTableExport.java:367) I've had no problems with sstable2json when using Cassandra 0.5. Is sstable2json broken in Cassandra 0.6.0-beta3 or am I doing something wrong?

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• Does the dealloc in Appdelegate calls or not?

  - by monish

  Hi guys, I the allocated arrays in the didFinishLaunching of my appdelegate.And I released those arrays in the dealloc of the appdelegate. My doubt here is does the dealloc of appdelegate calls?and does the arrays in the appdelegate releases or not? Anyone's help will be much appreciated. Thank you, Monish Kumar.

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• Java webservice does not return all struct array

  - by Aykut

  Hi I wrote a webservice which runs correctly. In the webservice, there is a class which contains other classes' arrays and the webservice returns this class's instance. for example public class cls1 implements Serializable{ cls2[] cls2Arr; cls3[] cls3Arr; } I fill this arrays (cls2Arr and cls3Arr) correctly in service side. When I read this arrays from client, I see only last item of arrays. I checked on the service side before the webservice returns, and the cls1 instance and everything else looked good. What can be a reason ? Thx

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• Optimizing sparse dot-product in C#

  - by Haggai

  Hello. I'm trying to calculate the dot-product of two very sparse associative arrays. The arrays contain an ID and a value, so the calculation should be done only on those IDs that are common to both arrays, e.g. <(1, 0.5), (3, 0.7), (12, 1.3) * <(2, 0.4), (3, 2.3), (12, 4.7) = 0.7*2.3 + 1.3*4.7 . My implementation (call it dict) currently uses Dictionaries, but it is too slow to my taste. double dot_product(IDictionary<int, double> arr1, IDictionary<int, double> arr2) { double res = 0; double val2; foreach (KeyValuePair<int, double> p in arr1) if (arr2.TryGetValue(p.Key, out val2)) res += p.Value * val2; return res; } The full arrays have about 500,000 entries each, while the sparse ones are only tens to hundreds entries each. I did some experiments with toy versions of dot products. First I tried to multiply just two double arrays to see the ultimate speed I can get (let's call this "flat"). Then I tried to change the implementation of the associative array multiplication using an int[] ID array and a double[] values array, walking together on both ID arrays and multiplying when they are equal (let's call this "double"). I then tried to run all three versions with debug or release, with F5 or Ctrl-F5. The results are as follows: debug F5: dict: 5.29s double: 4.18s (79% of dict) flat: 0.99s (19% of dict, 24% of double) debug ^F5: dict: 5.23s double: 4.19s (80% of dict) flat: 0.98s (19% of dict, 23% of double) release F5: dict: 5.29s double: 3.08s (58% of dict) flat: 0.81s (15% of dict, 26% of double) release ^F5: dict: 4.62s double: 1.22s (26% of dict) flat: 0.29s ( 6% of dict, 24% of double) I don't understand these results. Why isn't the dictionary version optimized in release F5 as do the double and flat versions? Why is it only slightly optimized in the release ^F5 version while the other two are heavily optimized? Also, since converting my code into the "double" scheme would mean lots of work - do you have any suggestions how to optimize the dictionary one? Thanks! Haggai

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• dynimically using pointer

  - by gcc

  Input: 3 1 2 n 4 5 d 1 21 30 x Output: 2: 4 5 21 30 Input: 3 j 3 34 6 22 10 51 n 1 2 j 1 3 4 5 n 6 7 x Output: 1: 1 2 3 4 5 2: 6 7 3: 34 6 22 10 51 'j': (Jump to array# command) 'd': (Delete array# command) 'n': (Next array command) 'x': (Exit command) #: (Integer number) int num_arrays; /* maximum number of arrays */ int **arrays; /* array of array pointers */ int *l_arrays; /* actual lengths of arrays */ int *c_arrays; /* actual capacities of arrays */ how can we write that code

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• An interview question on array comparison

  - by user288084

  There are two arrays with equivalent size. How to decide whether these two arrays contain the same set of elements, but the orders of these elements in the respective arrays are different. For instance. A = [a, b, c] B= [b, c, a]

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• dynamic memory allocation [closed]

  - by gcc

  i wanna write a program that creates (allocating memory) and manipulates (adding elements and increasing memory etc.) integer arrays dynamically according to given input sequences. input sequence which starts with the maximum number of arrays, includes integers to be put into arrays and some one letter characters which are commands to carry out some tasks (activating next array, deleting an array etc). also, i wanna create *c_arrays which is the address of the array whose elements are the actual capacities (How many integer slots are already allocated for an array?) of arrays how should i organize(set up) the algorithm?

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• Das T5-4 TPC-H Ergebnis naeher betrachtet

  - by Stefan Hinker

  Inzwischen haben vermutlich viele das neue TPC-H Ergebnis der SPARC T5-4 gesehen, das am 7. Juni bei der TPC eingereicht wurde.  Die wesentlichen Punkte dieses Benchmarks wurden wie gewohnt bereits von unserer Benchmark-Truppe auf  "BestPerf" zusammengefasst.  Es gibt aber noch einiges mehr, das eine naehere Betrachtung lohnt. Skalierbarkeit Das TPC raet von einem Vergleich von TPC-H Ergebnissen in unterschiedlichen Groessenklassen ab.  Aber auch innerhalb der 3000GB-Klasse ist es interessant: SPARC T4-4 mit 4 CPUs (32 Cores mit 3.0 GHz) liefert 205,792 QphH. SPARC T5-4 mit 4 CPUs (64 Cores mit 3.6 GHz) liefert 409,721 QphH. Das heisst, es fehlen lediglich 1863 QphH oder 0.45% zu 100% Skalierbarkeit, wenn man davon ausgeht, dass die doppelte Anzahl Kerne das doppelte Ergebnis liefern sollte.  Etwas anspruchsvoller, koennte man natuerlich auch einen Faktor von 2.4 erwarten, wenn man die hoehere Taktrate mit beruecksichtigt.  Das wuerde die Latte auf 493901 QphH legen.  Dann waere die SPARC T5-4 bei 83%.  Damit stellt sich die Frage: Was hat hier nicht skaliert?  Vermutlich der Plattenspeicher!  Auch hier lohnt sich eine naehere Betrachtung: Plattenspeicher Im Bericht auf BestPerf und auch im Full Disclosure Report der TPC stehen einige interessante Details zum Plattenspeicher und der Konfiguration.   In der Konfiguration der SPARC T4-4 wurden 12 2540-M2 Arrays verwendet, die jeweils ca. 1.5 GB/s Durchsatz liefert, insgesamt also eta 18 GB/s.  Dabei waren die Arrays offensichtlich mit jeweils 2 Kabeln pro Array direkt an die 24 8GBit FC-Ports des Servers angeschlossen.  Mit den 2x 8GBit Ports pro Array koennte man so ein theoretisches Maximum von 2GB/s erreichen.  Tatsaechlich wurden 1.5GB/s geliefert, was so ziemlich dem realistischen Maximum entsprechen duerfte. Fuer den Lauf mit der SPARC T5-4 wurden doppelt so viele Platten verwendet.  Dafuer wurden die 2540-M2 Arrays mit je einem zusaetzlichen Plattentray erweitert.  Mit dieser Konfiguration wurde dann (laut BestPerf) ein Maximaldurchsatz von 33 GB/s erreicht - nicht ganz das doppelte des SPARC T4-4 Laufs.  Um tatsaechlich den doppelten Durchsatz (36 GB/s) zu liefern, haette jedes der 12 Arrays 3 GB/s ueber seine 4 8GBit Ports liefern muessen.  Im FDR stehen nur 12 dual-port FC HBAs, was die Verwendung der Brocade FC Switches erklaert: Es wurden alle 4 8GBit ports jedes Arrays an die Switches angeschlossen, die die Datenstroeme dann in die 24 16GBit HBA ports des Servers buendelten.  Das theoretische Maximum jedes Storage-Arrays waere nun 4 GB/s.  Wenn man jedoch den Protokoll- und "Realitaets"-Overhead mit einrechnet, sind die tatsaechlich gelieferten 2.75 GB/s gar nicht schlecht.  Mit diesen Zahlen im Hinterkopf ist die Verdopplung des SPARC T4-4 Ergebnisses eine gute Leistung - und gleichzeitig eine gute Erklaerung, warum nicht bis zum 2.4-fachen skaliert wurde. Nebenbei bemerkt: Weder die SPARC T4-4 noch die SPARC T5-4 hatten in der gemessenen Konfiguration irgendwelche Flash-Devices. Mitbewerb Seit die T4 Systeme auf dem Markt sind, bemuehen sich unsere Mitbewerber redlich darum, ueberall den Eindruck zu hinterlassen, die Leistung des SPARC CPU-Kerns waere weiterhin mangelhaft.  Auch scheinen sie ueberzeugt zu sein, dass (ueber)grosse Caches und hohe Taktraten die einzigen Schluessel zu echter Server Performance seien.  Wenn ich mir nun jedoch die oeffentlichen TPC-H Ergebnisse ansehe, sehe ich dies: TPC-H @3000GB, Non-Clustered Systems System QphH SPARC T5-4 3.6 GHz SPARC T5 4/64 – 2048 GB 409,721.8 SPARC T4-4 3.0 GHz SPARC T4 4/32 – 1024 GB 205,792.0 IBM Power 780 4.1 GHz POWER7 8/32 – 1024 GB 192,001.1 HP ProLiant DL980 G7 2.27 GHz Intel Xeon X7560 8/64 – 512 GB 162,601.7 Kurz zusammengefasst: Mit 32 Kernen (mit 3 GHz und 4MB L3 Cache), liefert die SPARC T4-4 mehr QphH@3000GB ab als IBM mit ihrer 32 Kern Power7 (bei 4.1 GHz und 32MB L3 Cache) und auch mehr als HP mit einem 64 Kern Intel Xeon System (2.27 GHz und 24MB L3 Cache).  Ich frage mich, wo genau SPARC hier mangelhaft ist? Nun koennte man natuerlich argumentieren, dass beide Ergebnisse nicht gerade neu sind.  Nun, in Ermangelung neuerer Ergebnisse kann man ja mal ein wenig spekulieren: IBMs aktueller Performance Report listet die o.g. IBM Power 780 mit einem rPerf Wert von 425.5.  Ein passendes Nachfolgesystem mit Power7+ CPUs waere die Power 780+ mit 64 Kernen, verfuegbar mit 3.72 GHz.  Sie wird mit einem rPerf Wert von  690.1 angegeben, also 1.62x mehr.  Wenn man also annimmt, dass Plattenspeicher nicht der limitierende Faktor ist (IBM hat mit 177 SSDs getestet, sie duerfen das gerne auf 400 erhoehen) und IBMs eigene Leistungsabschaetzung zugrunde legt, darf man ein theoretisches Ergebnis von 311398 QphH@3000GB erwarten.  Das waere dann allerdings immer noch weit von dem Ergebnis der SPARC T5-4 entfernt, und gerade in der von IBM so geschaetzen "per core" Metric noch weniger vorteilhaft. In der x86-Welt sieht es nicht besser aus.  Leider gibt es von Intel keine so praktischen rPerf-Tabellen.  Daher muss ich hier fuer eine Schaetzung auf SPECint_rate2006 zurueckgreifen.  (Ich bin kein grosser Fan von solchen Kreuz- und Querschaetzungen.  Insb. SPECcpu ist nicht besonders geeignet, um Datenbank-Leistung abzuschaetzen, da fast kein IO im Spiel ist.)  Das o.g. HP System wird bei SPEC mit 1580 CINT2006_rate gelistet.  Das bis einschl. 2013-06-14 beste Resultat fuer den neuen Intel Xeon E7-4870 mit 8 CPUs ist 2180 CINT2006_rate.  Das ist immerhin 1.38x besser.  (Wenn man nur die Taktrate beruecksichtigen wuerde, waere man bei 1.32x.)  Hier weiter zu rechnen, ist muessig, aber fuer die ungeduldigen Leser hier eine kleine tabellarische Zusammenfassung: TPC-H @3000GB Performance Spekulationen System QphH* Verbesserung gegenueber der frueheren Generation SPARC T4-4 32 cores SPARC T4 205,792 2x SPARC T5-464 cores SPARC T5 409,721 IBM Power 780 32 cores Power7 192,001 1.62x IBM Power 780+ 64 cores Power7+  311,398* HP ProLiant DL980 G764 cores Intel Xeon X7560 162,601 1.38x HP ProLiant DL980 G780 cores Intel Xeon E7-4870    224,348* * Keine echten Resultate  - spekulative Werte auf der Grundlage von rPerf (Power7+) oder SPECint_rate2006 (HP) Natuerlich sind IBM oder HP herzlich eingeladen, diese Werte zu widerlegen.  Aber stand heute warte ich noch auf aktuelle Benchmark Veroffentlichungen in diesem Datensegment. Was koennen wir also zusammenfassen? Es gibt einige Hinweise, dass der Plattenspeicher der begrenzende Faktor war, der die SPARC T5-4 daran hinderte, auf jenseits von 2x zu skalieren Der Mythos, dass SPARC Kerne keine Leistung bringen, ist genau das - ein Mythos.  Wie sieht es umgekehrt eigentlich mit einem TPC-H Ergebnis fuer die Power7+ aus? Cache ist nicht der magische Performance-Schalter, fuer den ihn manche Leute offenbar halten. Ein System, eine CPU-Architektur und ein Betriebsystem jenseits einer gewissen Grenze zu skalieren ist schwer.  In der x86-Welt scheint es noch ein wenig schwerer zu sein. Was fehlt?  Nun, das Thema Preis/Leistung ueberlasse ich gerne den Verkaeufern ;-) Und zu guter Letzt: Nein, ich habe mich nicht ins Marketing versetzen lassen.  Aber manchmal kann ich mich einfach nicht zurueckhalten... Disclosure Statements The views expressed on this blog are my own and do not necessarily reflect the views of Oracle. TPC-H, QphH, $/QphH are trademarks of Transaction Processing Performance Council (TPC). For more information, see www.tpc.org, results as of 6/7/13. Prices are in USD. SPARC T5-4 409,721.8 QphH@3000GB, $3.94/QphH@3000GB, available 9/24/13, 4 processors, 64 cores, 512 threads; SPARC T4-4 205,792.0 QphH@3000GB, $4.10/QphH@3000GB, available 5/31/12, 4 processors, 32 cores, 256 threads; IBM Power 780 QphH@3000GB, 192,001.1 QphH@3000GB, $6.37/QphH@3000GB, available 11/30/11, 8 processors, 32 cores, 128 threads; HP ProLiant DL980 G7 162,601.7 QphH@3000GB, $2.68/QphH@3000GB available 10/13/10, 8 processors, 64 cores, 128 threads. SPEC and the benchmark names SPECfp and SPECint are registered trademarks of the Standard Performance Evaluation Corporation. Results as of June 18, 2013 from www.spec.org. HP ProLiant DL980 G7 (2.27 GHz, Intel Xeon X7560): 1580 SPECint_rate2006; HP ProLiant DL980 G7 (2.4 GHz, Intel Xeon E7-4870): 2180 SPECint_rate2006,

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• Identify memory leak in Java app

  - by Vincent Ma

  One important advantage of java is programer don't care memory management and GC handle it well. Maybe this is one reason why java is more popular. As Java programer you real dont care it? After you meet Out of memory you will realize it it’s not true. Java GC and memory is big topic you can get some information in here Today just let me show how to identify memory leak quickly. Let quickly review demo java code, it’s one kind of memory leak in our code, using static collection and always add some object. import java.util.ArrayList;import java.util.List; public class MemoryTest { public static void main(String[] args) { new Thread(new MemoryLeak(), "MemoryLeak").start(); }} class MemoryLeak implements Runnable { public static List<Integer> leakList = new ArrayList<Integer>(); public void run() { int num =0; while(true) { try { Thread.sleep(1); } catch (InterruptedException e) { } num++; Integer i = new Integer(num); leakList.add(i); } }} run it with java -verbose:gc -XX:+PrintGCDetails -Xmx60m -XX:MaxPermSize=160m MemoryTest after about some minuts you will get Exception in thread "MemoryLeak" java.lang.OutOfMemoryError: Java heap space at java.util.Arrays.copyOf(Arrays.java:2760) at java.util.Arrays.copyOf(Arrays.java:2734) at java.util.ArrayList.ensureCapacity(ArrayList.java:167) at java.util.ArrayList.add(ArrayList.java:351) at MemoryLeak.run(MemoryTest.java:25) at java.lang.Thread.run(Thread.java:619)Heap def new generation total 18432K, used 3703K [0x045e0000, 0x059e0000, 0x059e0000) eden space 16384K, 22% used [0x045e0000, 0x0497dde0, 0x055e0000) from space 2048K, 0% used [0x055e0000, 0x055e0000, 0x057e0000) to space 2048K, 0% used [0x057e0000, 0x057e0000, 0x059e0000) tenured generation total 40960K, used 40959K [0x059e0000, 0x081e0000, 0x081e0000) the space 40960K, 99% used [0x059e0000, 0x081dfff8, 0x081e0000, 0x081e0000) compacting perm gen total 12288K, used 2083K [0x081e0000, 0x08de0000, 0x10de0000) the space 12288K, 16% used [0x081e0000, 0x083e8c50, 0x083e8e00, 0x08de0000)No shared spaces configured. OK let us quickly identify it using JProfile Download JProfile in here  Run JProfile and attach MemoryTest get largest size of  Objects in Memory View in here is Integer then select Integer and go to Heap Walker. get GC Graph for this object  Then you get detail code raise this issue quickly now.  That is enjoy it.

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• Correct way to handle path-finding collision matrix

  - by Xander Lamkins

  Here is an example of me utilizing path finding. The red grid represents the grid utilized by my A* library to locate a distance. This picture is only an example, currently it is all calculated on the 1x1 pixel level (pretty darn laggy). I want to make it so that the farther I click, the less accurate it will be (split the map into larger grid pieces). Edit: as mentioned by Eric, this is not a required game mechanic. I am perfectly fine with any method that allows me to make this accurate while still fast. This isn't the really the topic of this question though. The problem I have is, my current library uses a two dimensional grid of integers. The higher the number in a cell, the more resistance for that grid tile. Currently I'm setting all unwalkable spots to Integer Max. Here is an example of what I want: I'm just not sure how I should set up the arrays of integers of the grid. Every time an element is added/removed to/from the game, it's collision details are updated in the table. Here is a picture of what the map looks like on my collision layer: I probably shouldn't be creating new arrays every time I have to do a path find because my game needs to support tons of PF at the same time. Should I have multiple arrays that are all updated when the dynamic elements are updated (a building is built/a building is destroyed). The problem I see with this is that it will probably make the creation and destruction of buildings a little more laggy than I would want because it would be setting the collision grid for each built in accuracy level. I would also have to add more/remove some arrays if I ever in the future changed the map size. Should I generate the new array based on an accuracy value every time I need to PF? The problem I see with this is that it will probably make any form of PF just as laggy because it will have to search through a MapWidth x MapHeight number of cells to shrink it all down. Or is there a better way? I'm certainly not the best at optimizing really anything. I've just started dealing with XNA so I'm not used to having optimization code really doing much of an affect until now... :( If you need code examples, please ask. I'll add it as an edit. EDIT: While this doesn't directly relate to the question, I figure the more information I provide, the better. To keep your units from moving as accurately to the players desired position, I've decided that once the unit PFs over to the less accurate grid piece, it will then PF on a more accurate level to the exact position requested.

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• Linux SW Raid: whole disk or per-partition?

  - by Steve Pomeroy

  I have inherited a machine which has 2 physical disks and uses Linux SW RAID(1). Both disks are partitioned and are are all individual arrays (/dev/md0, /dev/md6, etc.). Those arrays are then mounted (/boot, /home, etc. even /tmp). As RAID is designed to mitigate physical failures, is there any reason why one would use this technique over whole-disk arrays that are then partitioned (perhaps using LVM)? This seems prone to more potential issues, but may have some special properties that I haven't been able to glean. I'm planning on moving this setup to: disks?SWRAID(1)?LVM as I'll be making multiple VMs out of the one machine, but wanted to make sure I knew what I was doing when I got rid of the old setup.

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• Creating Persistent Drive Labels With UDEV Using /dev/disk/by-path

  - by Matt

  I have a new BackBlaze Pod (BackBlaze Pod 2.0). It has 45 3TB drives and they when I first set it up they were labeled /dev/sda through /dev/sdz and /dev/sdaa through /dev/sdas. I used mdadm to setup three really big 15 drive RAID6 arrays. However, since first setup a few weeks ago I had a couple of the hard drives fail on me. I've replaced them but now the arrays are complaining because they can't find the missing drives. When I list the the disks... ls -l /dev/sd* I see that /dev/sda /dev/sdf /dev/sdk /dev/sdp no longer appear and now there are 4 new ones... /dev/sdau /dev/sdav /dev/sdaw /dev/sdax I also just found that I can do this... ls -l /dev/disk/by-path/ total 0 lrwxrwxrwx 1 root root 10 Sep 19 18:08 pci-0000:02:04.0-scsi-0:0:0:0 -> ../../sdau lrwxrwxrwx 1 root root 9 Sep 19 18:08 pci-0000:02:04.0-scsi-0:1:0:0 -> ../../sdb lrwxrwxrwx 1 root root 9 Sep 19 18:08 pci-0000:02:04.0-scsi-0:2:0:0 -> ../../sdc lrwxrwxrwx 1 root root 9 Sep 19 18:08 pci-0000:02:04.0-scsi-0:3:0:0 -> ../../sdd lrwxrwxrwx 1 root root 9 Sep 19 18:08 pci-0000:02:04.0-scsi-0:4:0:0 -> ../../sde lrwxrwxrwx 1 root root 10 Sep 19 18:08 pci-0000:02:04.0-scsi-2:0:0:0 -> ../../sdae lrwxrwxrwx 1 root root 9 Sep 19 18:08 pci-0000:02:04.0-scsi-2:1:0:0 -> ../../sdg lrwxrwxrwx 1 root root 9 Sep 19 18:08 pci-0000:02:04.0-scsi-2:2:0:0 -> ../../sdh lrwxrwxrwx 1 root root 9 Sep 19 18:08 pci-0000:02:04.0-scsi-2:3:0:0 -> ../../sdi lrwxrwxrwx 1 root root 9 Sep 19 18:08 pci-0000:02:04.0-scsi-2:4:0:0 -> ../../sdj lrwxrwxrwx 1 root root 10 Sep 19 18:08 pci-0000:02:04.0-scsi-3:0:0:0 -> ../../sdav lrwxrwxrwx 1 root root 9 Sep 19 18:08 pci-0000:02:04.0-scsi-3:1:0:0 -> ../../sdl lrwxrwxrwx 1 root root 9 Sep 19 18:08 pci-0000:02:04.0-scsi-3:2:0:0 -> ../../sdm lrwxrwxrwx 1 root root 9 Sep 19 18:08 pci-0000:02:04.0-scsi-3:3:0:0 -> ../../sdn lrwxrwxrwx 1 root root 9 Sep 19 18:08 pci-0000:02:04.0-scsi-3:4:0:0 -> ../../sdo lrwxrwxrwx 1 root root 10 Sep 19 18:08 pci-0000:04:04.0-scsi-0:0:0:0 -> ../../sdax lrwxrwxrwx 1 root root 9 Sep 19 18:08 pci-0000:04:04.0-scsi-0:1:0:0 -> ../../sdq lrwxrwxrwx 1 root root 9 Sep 19 18:08 pci-0000:04:04.0-scsi-0:2:0:0 -> ../../sdr lrwxrwxrwx 1 root root 9 Sep 19 18:08 pci-0000:04:04.0-scsi-0:3:0:0 -> ../../sds lrwxrwxrwx 1 root root 9 Sep 19 18:08 pci-0000:04:04.0-scsi-0:4:0:0 -> ../../sdt lrwxrwxrwx 1 root root 9 Sep 19 18:08 pci-0000:04:04.0-scsi-2:0:0:0 -> ../../sdu lrwxrwxrwx 1 root root 9 Sep 19 18:08 pci-0000:04:04.0-scsi-2:1:0:0 -> ../../sdv lrwxrwxrwx 1 root root 9 Sep 19 18:08 pci-0000:04:04.0-scsi-2:2:0:0 -> ../../sdw lrwxrwxrwx 1 root root 9 Sep 19 18:08 pci-0000:04:04.0-scsi-2:3:0:0 -> ../../sdx lrwxrwxrwx 1 root root 9 Sep 19 18:08 pci-0000:04:04.0-scsi-2:4:0:0 -> ../../sdy lrwxrwxrwx 1 root root 9 Sep 19 18:08 pci-0000:04:04.0-scsi-3:0:0:0 -> ../../sdz I didn't list them all....you can see the problem above. They're sorted by scsi id here but sda is missing...replaced by sdau...etc... So obviously the arrays are complaining. Is it possible to get Linux to reread the drive labels in the correct order or am I screwed? My initial design with 15 drive arrays is not ideal. With 3TB drives the rebuild times were taking 3 or 4 days....maybe more. I'm scrapping the whole design and I think I am going to go with 6 x 7 RAID5 disk arrays and 3 hot spares to make the arrays a bit easier to manage and shorten the rebuild times. But I'd like to clean up the drive labels so they aren't out of order. I haven't figured out how to do this yet. Does anyone know how to get this straightened out? Thanks, Matt

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• "Verifying DMI Pool" hang caused by raid array..

  - by Ling

  Hi Experts, I have a problem, I obtained a new server with 4 hard drives (2 500 gig, 2 two TB), and an adeptec RAID card. I arranged them in two arrays with RAID 1 (500 gigs together as primary and the 2 TB drives for lots of data). When both arrays are configured, the server hangs while booting at message "Verifying DMI Pool", however if I remove the second array from the configuration the server boots fine. I have checked they are both on different channels, I have disabled all other peripherals from the boot menu and ensured the hard drive is #1. I have booted into the linux rescue mode and checked that it is reading both arrays fine. What else could be causing these problems? Thanks

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• How do you automap List<float> or float[] with Fluent NHibernate?

  - by Tom Bushell

  Having successfully gotten a sample program working, I'm now starting to do Real Work with Fluent NHibernate - trying to use Automapping on my project's class heirarchy. It's a scientific instrumentation application, and the classes I'm mapping have several properties that are arrays of floats e.g. private float[] _rawY; public virtual float[] RawY { get { return _rawY; } set { _rawY = value; } } These arrays can contain a maximum of 500 values. I didn't expect Automapping to work on arrays, but tried it anyway, with some success at first. Each array was auto mapped to a BLOB (using SQLite), which seemed like a viable solution. The first problem came when I tried to call SaveOrUpdate on the objects containing the arrays - I got "No persister for float[]" exceptions. So my next thought was to convert all my arrays into ILists e.g. public virtual IList<float> RawY { get; set; } But now I get: NHibernate.MappingException: Association references unmapped class: System.Single Since Automapping can deal with lists of complex objects, it never occured to me it would not be able to map lists of basic types. But after doing some Googling for a solution, this seems to be the case. Some people seem to have solved the problem, but the sample code I saw requires more knowledge of NHibernate than I have right now - I didn't understand it. Questions: 1. How can I make this work with Automapping? 2. Also, is it better to use arrays or lists for this application? I can modify my app to use either if necessary (though I prefer lists). Edit: I've studied the code in Mapping Collection of Strings, and I see there is test code in the source that sets up an IList of strings, e.g. public virtual IList<string> ListOfSimpleChildren { get; set; } [Test] public void CanSetAsElement() { new MappingTester<OneToManyTarget>() .ForMapping(m => m.HasMany(x => x.ListOfSimpleChildren).Element("columnName")) .Element("class/bag/element").Exists(); } so this must be possible using pure Automapping, but I've had zero luck getting anything to work, probably because I don't have the requisite knowlege of manually mapping with NHibernate. Starting to think I'm going to have to hack this (by encoding the array of floats as a single string, or creating a class that contains a single float which I then aggregate into my lists), unless someone can tell me how to do it properly. End Edit Here's my CreateSessionFactory method, if that helps formulate a reply... private static ISessionFactory CreateSessionFactory() { ISessionFactory sessionFactory = null; const string autoMapExportDir = "AutoMapExport"; if( !Directory.Exists(autoMapExportDir) ) Directory.CreateDirectory(autoMapExportDir); try { var autoPersistenceModel = AutoMap.AssemblyOf<DlsAppOverlordExportRunData>() .Where(t => t.Namespace == "DlsAppAutomapped") .Conventions.Add( DefaultCascade.All() ) ; sessionFactory = Fluently.Configure() .Database(SQLiteConfiguration.Standard .UsingFile(DbFile) .ShowSql() ) .Mappings(m => m.AutoMappings.Add(autoPersistenceModel) .ExportTo(autoMapExportDir) ) .ExposeConfiguration(BuildSchema) .BuildSessionFactory() ; } catch (Exception e) { Debug.WriteLine(e); } return sessionFactory; }

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• search a collection for a specific keyword

  - by icelated

  What i want to do is search a hashset with a keyword.. I have 3 classes... main() Library Item(CD, DVD,Book classes) In library i am trying to do my search of the items in the hashsets.. In Item class is where i have the getKeywords function.. here is the Items class... import java.io.PrintStream; import java.util.Collection; import java.util.*; class Item { private String title; private String [] keywords; public String toString() { String line1 = "title: " + title + "\n" + "keywords: " + Arrays.toString(keywords); return line1; } public void print() { System.out.println(toString()); } public Item() { } public Item(String theTitle, String... theKeyword) { this.title = theTitle; this.keywords = theKeyword; } public String getTitle() { return title; } public String [] getKeywords() { return keywords; } } class CD extends Item { private String artist; private String [] members; // private String [] keywords; private int number; public CD(String theTitle, String theBand, int Snumber, String... keywords) { super(theTitle, keywords); this.artist = theBand; this.number = Snumber; // this.keywords = keywords; } public void addband(String... member) { this.members = member; } public String getArtist() { return artist; } public String [] getMembers() { return members; } // public String [] getKeywords() // { // return keywords; //} public String toString() { return "-Music-" + "\n" + "band: " + artist + "\n" + "# songs: " + number + "\n" + "members: " + Arrays.toString(members) + "\n" + super.toString() // + "keywords: " + Arrays.toString(keywords) + "\n" + "\n" ; } public void print() { System.out.println(toString()); } } class DVD extends Item { private String director; private String [] cast; private int scenes; // private String [] keywords; public DVD(String theTitle, String theDirector, int nScenes, String... keywords) { super(theTitle, keywords); this.director = theDirector; this.scenes = nScenes; // this.keywords = keywords; } public void addmoviecast(String... members) { this.cast = members; } public String [] getCast() { return cast; } public String getDirector() { return director; } // public String [] getKeywords() // { // return keywords; // } public String toString() { return "-Movie-" + "\n" + "director: " + director + "\n" + "# scenes: " + scenes + "\n" + "cast: " + Arrays.toString(cast) + "\n" + super.toString() // + "keywords: " + Arrays.toString(keywords) + "\n" + "\n" ; } public void print() { System.out.println(toString()); } } class Book extends Item { private String author; private int pages; public Book(String theTitle, String theAuthor, int nPages, String... keywords) { super(theTitle, keywords); this.author = theAuthor; this.pages = nPages; // this.keywords = keywords; } public String getAuthor() { return author; } //public String [] getKeywords() // { // return keywords; //} public void print() { System.out.println(toString()); } public String toString() { return "-Book-" + "\n" + "Author: " + author + "\n" + "# pages " + pages + "\n" + super.toString() // + "keywords: " + Arrays.toString(keywords) + "\n" + "\n" ; } } I hope i didnt confuse you? I need help with the itemsForKeyword(String keyword) function.. the first keyword being passed in is "science fiction" and i want to search the keywords in the sets and return the matches.. What am i doing so wrong? Thank you

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• Constructing a Binary Tree from its traversals

  - by user991710

  I'm trying to construct a binary tree (unbalanced), given its traversals. I'm currently doing preorder + inorder but when I figure this out postorder will be no issue at all. I realize there are some question on the topic already but none of them seemed to answer my question. I've got a recursive method that takes the Preorder and the Inorder of a binary tree to reconstruct it, but is for some reason failing to link the root node with the subsequent children. Note: I don't want a solution. I've been trying to figure this out for a few hours now and even jotted down the recursion on paper and everything seems fine... so I must be missing something subtle. Here's the code: public static <T> BinaryNode<T> prePlusIn( T[] pre, T[] in) { if(pre.length != in.length) throw new IllegalArgumentException(); BinaryNode<T> base = new BinaryNode(); base.element = pre[0]; // * Get root from the preorder traversal. int indexOfRoot = 0; if(pre.length == 0 && in.length == 0) return null; if(pre.length == 1 && in.length == 1 && pre[0].equals(in[0])) return base; // * If both arrays are of size 1, element is a leaf. for(int i = 0; i < in.length -1; i++){ if(in[i].equals(base.element)){ // * Get the index of the root indexOfRoot = i; // in the inorder traversal. break; } // * If we cannot, the tree cannot be constructed as the traversals differ. else throw new IllegalArgumentException(); } // * Now, we recursively set the left and right subtrees of // the above "base" root node to whatever the new preorder // and inorder traversals end up constructing. T[] preleft = Arrays.copyOfRange(pre, 1, indexOfRoot + 1); T[] preright = Arrays.copyOfRange(pre, indexOfRoot + 1, pre.length); T[] inleft = Arrays.copyOfRange(in, 0, indexOfRoot); T[] inright = Arrays.copyOfRange(in, indexOfRoot + 1, in.length); base.left = prePlusIn( preleft, inleft); // * Construct left subtree. base.right = prePlusIn( preright, inright); // * Construc right subtree. return base; // * Return fully constructed tree } Basically, I construct additional arrays that house the pre- and inorder traversals of the left and right subtree (this seems terribly inefficient but I could not think of a better way with no helpers methods). Any ideas would be quite appreciated. Side note: While debugging it seems that the root note never receives the connections to the additional nodes (they remain null). From what I can see though, that should not happen... EDIT: To clarify, the method is throwing the IllegalArgumentException @ line 21 (else branch of the for loop, which should only be thrown if the traversals contain different elements.

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• Rotating a view of a chunked 2d tilemap

  - by Danie Clawson

  I'm working on a top-down (oblique) tile-based engine. I would like for the tiles to have a definable height in the world, with Characters being occluded by them, etc. This has led to a desire to be able to "rotate" the view of the world, even though I'm using all hand-drawn graphics and blitting. Therefor, I need to rotate the actual world itself, or change how the Camera traverses these arrays. How can, or should, I create individual rotations of 90 degrees, when I have multi-dimensional arrays? Is it faster to actually rotate the array, to access it differently, or to create pre-computed accessor(?) arrays, something like how my chunks work? How can I rotate an individual chunk, or set of chunks? Currently I establish my tile grid like this (tile height not included): function Surface(WIDTH, HEIGHT) { WIDTH = Math.max(WIDTH-(WIDTH%TPC), TPC); HEIGHT = Math.max(HEIGHT-(HEIGHT%TPC), TPC); this.tiles = []; this.chunks = []; //Establish tiles for(var x = 0; x < WIDTH; x++) { var col = [], ch_x = Math.floor(x/TPC); if(!this.chunks[ch_x]) this.chunks.push([]); for(var y = 0; y < HEIGHT; y++) { var tile = new Tile(x, y), ch_y = Math.floor(y/TPC); if(!this.chunks[ch_x][ch_y]) this.chunks[ch_x].push([]); this.chunks[ch_x][ch_y].push(tile); col.push(tile); } this.tiles.push(col); } }; Even some basic advice on my data struct would be much appreciated.

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• Creating properly aligned partitions on a replacement disk

  - by Marius Gedminas

  I've a typical small office server with two hard disks configured for RAID-1 (mirroring). Each disk has several partitions: one for swap, the others paired in several /dev/mdX arrays. Every couple of years one of the disks dies and is replaced. The replacement typically goes something like this: # copy partition table from the remaining good disk to the empty replacement disk # (instead of /dev/good_disk and /dev/new_disk I use /dev/sda and /dev/sdb, as appropriate) sfdisk -d /dev/good_disk | sfdisk /dev/new_disk # install boot loader grub-install /dev/new_disk # create swap partition reusing the same UUID, so I don't need to edit /etc/fstab mkswap /dev/new_disk1 -U xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx # hot-add the new partitions to my RAID arrays mdadm /dev/md0 -a /dev/new_disk2 mdadm /dev/md1 -a /dev/new_disk5 mdadm /dev/md2 -a /dev/new_disk6 mdadm /dev/md3 -a /dev/new_disk7 mdadm /dev/md4 -a /dev/new_disk8 The disks were originally partitioned with cfdisk back in 2009, and so the partition table is aligned traditionally to cylinder boundaries (255 heads * 63 sectors). This is not the optimum configuration for new 4K-sector drives. My question is: how can I create a set of partitions for the new disk and ensure they're properly aligned, and have correct sizes for my RAID arrays (rounding up is acceptable, I suppose, but rounding down is definitely not)?

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• Space-efficient data structures for broad-phase collision detection

  - by Marian Ivanov

  As far as I know, these are three types of data structures that can be used for collision detection broadphase: Unsorted arrays: Check every object againist every object - O(n^2) time; O(log n) space. It's so slow, it's useless if n isn't really small. for (i=1;i<objects;i++){ for(j=0;j<i;j++) narrowPhase(i,j); }; Sorted arrays: Sort the objects, so that you get O(n^(2-1/k)) for k dimensions O(n^1.5) for 2d and O(n^1.67) for 3d and O(n) space. Assuming the space is 2D and sortedArray is sorted so that if the object begins in sortedArray[i] and another object ends at sortedArray[i-1]; they don't collide Heaps of stacks: Divide the objects between a heap of stacks, so that you only have to check the bucket, its children and its parents - O(n log n) time, but O(n^2) space. This is probably the most frequently used approach. Is there a way of having O(n log n) time with less space? When is it more efficient to use sorted arrays over heaps and vice versa?

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• a flexible data structure for geometries

  - by AkiRoss

  What data structure would you use to represent meshes that are to be altered (e.g. adding or removing new faces, vertices and edges), and that have to be "studied" in different ways (e.g. finding all the triangles intersecting a certain ray, or finding all the triangles "visible" from a given point in the space)? I need to consider multiple aspects of the mesh: their geometry, their topology and spatial information. The meshes are rather big, say 500k triangles, so I am going to use the GPU when computations are heavy. I tried using arrays with vertices and arrays with indices, but I do not love adding and removing vertices from them. Also, using arrays totally ignore spatial and topological information, which I may need studying the mesh. So, I thought about using custom double-linked list data structures, but I believe doing so will require me to copy the data to array buffers before going on the GPU. I also thought about using BST, but not sure it fits. Any help is appreciated. If I have been too fuzzy and you require other information feel free to ask.

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• why gcc emits segmentation ,after my code run

  - by gcc

  every time ,why have I encountered with segmentation fault ? still,I have not found my fault sometimes, gcc emits segmentation fault ,sometimes, memory satck limit is exceeded I think you will understand (easily) what is for that code void my_main() { char *tutar[50],tempc; int i=0,temp,g=0,a=0,j=0,d=1,current=0,command=0,command2=0; do{ tutar[i]=malloc(sizeof(int)); scanf("%s",tutar[i]); temp=*tutar[i]; } while(temp=='x'); i=0; num_arrays=atoi(tutar[i]); i=1; tempc=*tutar[i]; if(tempc!='x' && tempc!='d' && tempc!='a' && tempc!='j') { current=1; arrays[current]=malloc(sizeof(int)); l_arrays[current]=calloc(1,sizeof(int)); c_arrays[current]=calloc(1,sizeof(int));} i=1; current=1; while(1) { tempc=*tutar[i]; if(tempc=='x') break; if(tempc=='n') { ++current; arrays[current]=malloc(sizeof(int)); l_arrays[current]=calloc(1,sizeof(int)); c_arrays[current]=calloc(1,sizeof(int)); ++i; continue; } if(tempc=='d') { ++i; command=atoi(tutar[i])-1; free(arrays[command]); free(l_arrays[command]); free(c_arrays[command]); ++i; continue; } if(tempc=='j') { ++i; current=atoi(tutar[i])-1; if(arrays[current]==NULL) { arrays[current]=malloc(sizeof(int)); l_arrays[current]=calloc(1,sizeof(int)); c_arrays[current]=calloc(1,sizeof(int)); ++i; } else { a=l_arrays[current]; j=l_arrays[current]; ++i;} continue; } } }

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• No acceleration for OpenGL and ImportError for modules that exist

  - by Aku

  I'm writing a program using wxPython and OpenGL. The program works, but without any antialiasing, and I get these error messages: (I'm using ArchLinux) INFO:OpenGL.acceleratesupport:No OpenGL_accelerate module loaded: No module named OpenGL_accelerate INFO:OpenGL.formathandler:Unable to load registered array format handler numpy: Traceback (most recent call last): File "/usr/lib/python2.6/site-packages/OpenGL/arrays/formathandler.py", line 44, in loadPlugin plugin_class = entrypoint.load() File "/usr/lib/python2.6/site-packages/OpenGL/plugins.py", line 14, in load return importByName( self.import_path ) File "/usr/lib/python2.6/site-packages/OpenGL/plugins.py", line 28, in importByName module = __import__( ".".join(moduleName), {}, {}, moduleName) File "/usr/lib/python2.6/site-packages/OpenGL/arrays/numpymodule.py", line 11, in <module> raise ImportError( """No numpy module present: %s"""%(err)) ImportError: No numpy module present: No module named numpy INFO:OpenGL.formathandler:Unable to load registered array format handler numeric: Traceback (most recent call last): File "/usr/lib/python2.6/site-packages/OpenGL/arrays/formathandler.py", line 44, in loadPlugin plugin_class = entrypoint.load() File "/usr/lib/python2.6/site-packages/OpenGL/plugins.py", line 14, in load return importByName( self.import_path ) File "/usr/lib/python2.6/site-packages/OpenGL/plugins.py", line 28, in importByName module = __import__( ".".join(moduleName), {}, {}, moduleName) File "/usr/lib/python2.6/site-packages/OpenGL/arrays/numeric.py", line 15, in <module> raise ImportError( """No Numeric module present: %s"""%(err)) ImportError: No Numeric module present: No module named Numeric However, when I look into my site-packages folder, I see those modules present there. I have a wxPython demo program that uses GLCanvas, and it works fine, without any errors. My program is quite similar to the GLCanvas demo, involving just translations, rotations, drawing quads and some basic lighting. What am I doing wrong here? (The code is over 200 lines, if necessary I'll edit this and put it here.)

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• Matlab and .net problem with character string function input

  - by Peter

  I have a MATLAB function that I've compiled into a .net library. The function is a simple one that takes a character array as an input and a numeric array as output: function insert = money(dateLimit) .. insert = [1 2]; The function works fine when no function arguments are specified (a default argument is provided inside the function) Dim sf As New SpreadFinder.SpreadFinder Dim output = sf.money() As soon as an argument is specified .net complains. I'm thinking this should be easy and has been done before but searching through MATLAB documentation doesn't offer much help. Here's what I've tried. The sf.money() overload for the function with arguments is (numArgsOut as Integer, argsOut as MWArray, argsIn as MWArray) and hence that's what I've tried. What am I missing? Dim sf As New SpreadFinder.SpreadFinder Dim inputArgs(1) As Arrays.MWCharArray Dim dateLimitString As String = "some string" inputArgs(0) = New Arrays.MWCharArray(dateLimitString) Dim outputArgs(1) As Arrays.MWNumericArray outputArgs(0) = New Arrays.MWNumericArray() sf.money(1, outputArgs, inputArgs) Gives System.NullReferenceException : Object reference not set to an instance of an object. at MathWorks.MATLAB.NET.Utility.MWMCR.EvaluateFunction(String functionName, Int32 numArgsOut, Int32 numArgsIn, MWArray[] argsIn) at MathWorks.MATLAB.NET.Utility.MWMCR.EvaluateFunction(String functionName, Int32 numArgsOut, MWArray[]& argsOut, MWArray[] argsIn) at SpreadFinder.SpreadFinder.money(Int32 numArgsOut, MWArray[]& argsOut, MWArray[] argsIn)

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• Range-based `for` statement definition redundancy

  - by GMan - Save the Unicorns

  Looking at n3092, in §6.5.4 we find the equivalency for a range-based for loop. It then goes on to say what __begin and __end are equal to. It differentiates between arrays and other types, and I find this redundant (aka, confusing). It says for arrays types that __begin and __end are what you expect: a pointer to the first and a pointer to one-past the end. Then for other types, __begin and __end are equal to begin(__range) and end(__range), with ADL. Namespace std is associated, in order to find the std::begin and std::end defined in <iterator>, §24.6.5. However, if we look at the definition of std::begin and std::end, they are both defined for arrays as well as container types. And the array versions do exactly the same as above: pointer to the first, pointer to one-past the end. Why is there a need to differentiate arrays from other types, when the definition given for other types would work just as well, finding std::begin and std::end? Some abridged quotes for convenience: §24.6.5 The range-based for statement — if _RangeT is an array type, begin-expr and end-expr are __range and __range + __bound, respectively, where __bound is the array bound. If _RangeT is an array of unknown size or an array of incomplete type, the program is ill-formed. — otherwise, begin-expr and end-expr are begin(_range) and end(_range), respectively, where begin and end are looked up with argument-dependent lookup (3.4.2). For the purposes of this name lookup, namespace std is an associated namespace. and §24.6.5 range access template T* begin(T (&array)[N]); Returns: array. template T* end(T (&array)[N]); Returns: array + N.

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