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  • printing out dictionnaires

    - by kyril
    I have a rather specific question: I want to print out characters at a specific place using the \033[ syntax. This is what the code below should do: (the dict cells has the same keys as coords but with either '*' or '-' as value.) coords = {'x'+str(x)+'y'+str(y) : (x,y) for x,y, in itertools.product(range(60), range(20))} for key, value in coords.items(): char = cells[key] x,y = value HORIZ=str(x) VERT=str(y) char = str(char) print('\033['+VERT+';'+HORIZ+'f'+char) However, I noticed that if I put this into a infinite while loop, it does not always prints the same characters at the same position. There are only slight changes, but it deletes some and puts them back in after some loops. I already tried it with lists, and there it seems to behave just fine, so I tend to think it has something todo with the dict, but I can not figure out what it could be. You can see the Problem in a console here: SharedConsole.I am happy for every tip on this matter. On a related topic: After the printing, some changes should be made at the values of the cells dict, but for reason unknown to me, the only the first two rules are executed and the rest is ignored. The rules should test how many neighbours (which is in population) are around the cell and apply the according rule. In my implemention of this I have some kind of weird tumor growth (which should not happen, as if there more than three around they should the cell should die) (see FreakingTumor): if cells_copy [coord] == '-': if population == 3: cells [coord] = '*' if cells_copy [coord] == '*': if population > 3: cells [coord] = '-' elif population <= 1: cells [coord] = '-' elif population == 2 or 3: cells [coord] = '*' I checked the population variable several times, so I am quite sure that is not the matter. I am sorry for the slow consoles. Thanks in advance! Kyril

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  • Using MPI_Type_Vector and MPI_Gather, in C.

    - by Goloneg
    Hi, I am trying to multiply square matrices in parallele with MPI. I use a MPI_Type_vector to send square submatrixes (arrays of float) to the processes, so they can calculate subproducts. Then, for the next iterations, these submatrices are send to neighbours processes as MPI_Type_contiguous (the whole submatrix is sent). This part is working as expected, and local results are corrects. Then, I use MPI_Gather with the contiguous types to send all local results back to the root process. The problem is, the final matrix is build (obviously, by this method) line by line instead of submatrix by submatrix. I wrote an ugly procedure rearranging the final matrix, but I would like to know if there is a direct way of performing the "inverse" operation of sending MPI_Type_vectors (i.e., sending an array of values and directly arranging it in a subarray form in the receiving array). An example, to try and clarify my long text : A[16] and B[16] are 4x4 matrices to be multiplied ; C[16] will contain the result ; 4 processes are used (Pi with i from 0 to 3) : Pi gets two 2x2 submatrices : subAi[4] and subBi[4] ; their product is stored locally in subCi[4]. For instance, P0 gets : subA0[4] containing A[0], A[1], A[4] and A[5] ; subB0[4] containing B[0], B[1], B[4] and B[5]. After everything is calculed, root process gathers all subCi[4]. Then C[16] contains : [ subC0[0], subC0[1], subC0[2], subC0[3], subC1[0], subC1[1], subC1[2], subC1[3], subC2[0], subC2[1], subC2[2], subC2[3], subC3[0], subC3[1], subC3[2], subC3[3]] and I would like it to be : [ subC0[0], subC0[1], subC1[0], subC1[1], subC0[2], subC0[3], subC1[2], subC1[3], subC2[0], subC2[1], subC3[0], subC3[1], subC2[2], subC2[3], subC3[2], subC3[3]] without further operation. Does someone know a way ? Thanks for your advices.

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  • MBPro, mid 2010 can't see Dlink DIR655 signal after sleep etc

    - by user88114
    This is my son's MBP 7,1 running Snow Leopard 10.6.7. Router signal is fine since iPad, Wintel on same table 20 feet from router are fine. the MBP however frequently wakes and fails to find the internet. iStumbler can see 1 neighbours hub and my garden hub are there but can't get to the normal DIR655 wifi... no ping no en0 or en1 device seems to exist. Airport off and on does not help. He just resets router and it all works but this does not please me! I must admit the winter sometimes seems to loose connect too, but less so. The DIR655 (hardware rev A3) is on the original EU firmware 1.10, I'm cautious about jumping to latest 1.31EU since no downgrade seems to be possible and that feels a bit risky as so much is set up and working fine. If I use the DIR655 admin web and release the lease the MBP has then wake it all worked OK. So I suspect lease timing/locking issue but unsure how to check up, plus why iStumbler seems to say the network is not visible at all when I sit on the iPad right next to it just fine.. I do not think there are any channel overlaps and we also have RFquiet DECT phones (Orchid) that are silent until lifted or called. Anyway signals all show low interference and high throughput except for this failure to connect. Just walked the MBP to the garden office and iStumbler now sees the more distant DIR655 signal although it will not connect to it (does not show under Sys Prefs NetNetwork names) even after airport off & on... It also refuses to connect to my garden network (an old Belkin acting as AP wired to DIR655), the signal it can see and even net name in Sys Prefs NetNetwork names (2 mins later):NOW both names ARE visible, but both fail to accept the correct WPA2 password and keep asking again after failing to connect. IT ALL MAKES NO SENSE TO ME. Just revoked the lease for the MBP on DIR655 and no changes although this seemed to help MBP wake into connection 1 hour ago. OK a bit of walking about to report. Carried MBP across garden towards DIR655, a few other wifis show up on iStumbler, low signals all channel 1. Right next to DIR655 but iStumbler not showing it, although most other wifi's have gone. I'd say iStubler is suffering timeouts&hangs but hard to be sure. Lots of attempts to Airport on/off, join other etc and suddenly I get to connect, get given new IP (I revoked), can browse. Walk away, connection drops quite soon at 30 feet then reconnected briefly then died again. MUST ATTEND ELSEWHERE FOR A BIT...

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  • Airport Express chokes Wi-Fi for a few seconds, several times per hour. Any idea why?

    - by user13727
    I'm using a MacBookPro connected to an AiportExpress' Wi-FI network. Every once in a while, the Wi-Fi will choke up and either drop some packets, or lag horribly for several seconds. I'm losing hair over this because every time I chat on Skype, the call hangs randomly due to this problem. Any idea what's wrong? Some more details: two networks are set up: 2.4Ghz and 5Ghz, and the issue happens on both the network uses WPA2 Personal for security the Airport is in the same room with my computer the Airport is fairly new, bought this summer, model number off the back: A1392 tried connecting to a neighbours wifi to see if it's a problem with my computer, or interference. It's not, it doesn't happen on their network. tried resetting it several times tried changing channels manually Ping results are below, so you can see what I'm talking about. EDIT: 10.0.1.1 is the Airport's IP 64 bytes from 10.0.1.1: icmp_seq=1795 ttl=255 time=0.813 ms 64 bytes from 10.0.1.1: icmp_seq=1796 ttl=255 time=3.335 ms 64 bytes from 10.0.1.1: icmp_seq=1797 ttl=255 time=3.403 ms 64 bytes from 10.0.1.1: icmp_seq=1798 ttl=255 time=3.414 ms 64 bytes from 10.0.1.1: icmp_seq=1799 ttl=255 time=3.227 ms 64 bytes from 10.0.1.1: icmp_seq=1800 ttl=255 time=3.274 ms 64 bytes from 10.0.1.1: icmp_seq=1801 ttl=255 time=3.253 ms 64 bytes from 10.0.1.1: icmp_seq=1802 ttl=255 time=3.292 ms >>>> choke starts <<< 64 bytes from 10.0.1.1: icmp_seq=1803 ttl=255 time=53.977 ms 64 bytes from 10.0.1.1: icmp_seq=1804 ttl=255 time=35.049 ms 64 bytes from 10.0.1.1: icmp_seq=1805 ttl=255 time=19.820 ms >>>> choke ends <<< 64 bytes from 10.0.1.1: icmp_seq=1806 ttl=255 time=0.716 ms 64 bytes from 10.0.1.1: icmp_seq=1807 ttl=255 time=0.705 ms 64 bytes from 10.0.1.1: icmp_seq=1808 ttl=255 time=0.919 ms 64 bytes from 10.0.1.1: icmp_seq=1809 ttl=255 time=0.659 ms 64 bytes from 10.0.1.1: icmp_seq=1810 ttl=255 time=0.877 ms 64 bytes from 10.0.1.1: icmp_seq=1811 ttl=255 time=0.679 ms 64 bytes from 10.0.1.1: icmp_seq=1812 ttl=255 time=0.854 ms 64 bytes from 10.0.1.1: icmp_seq=1813 ttl=255 time=0.644 ms 64 bytes from 10.0.1.1: icmp_seq=1814 ttl=255 time=3.779 ms ... time passes .. 64 bytes from 10.0.1.1: icmp_seq=1599 ttl=255 time=0.674 ms 64 bytes from 10.0.1.1: icmp_seq=1600 ttl=255 time=0.930 ms 64 bytes from 10.0.1.1: icmp_seq=1601 ttl=255 time=0.665 ms 64 bytes from 10.0.1.1: icmp_seq=1602 ttl=255 time=1.085 ms Request timeout for icmp_seq 1603 Request timeout for icmp_seq 1604 64 bytes from 10.0.1.1: icmp_seq=1605 ttl=255 time=104.969 ms 64 bytes from 10.0.1.1: icmp_seq=1606 ttl=255 time=11.521 ms 64 bytes from 10.0.1.1: icmp_seq=1607 ttl=255 time=0.926 ms 64 bytes from 10.0.1.1: icmp_seq=1608 ttl=255 time=0.993 ms 64 bytes from 10.0.1.1: icmp_seq=1609 ttl=255 time=0.745 ms And the Signal-Noise ratio:

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  • How to get sound on macbook pro 4,1

    - by Thomas
    I have just installed Xubuntu 12.04.2. My soundcard is detected: thomas@thomas-pc:~$ sudo aplay -l **** List of PLAYBACK Hardware Devices **** Home directory /home/thomas not ours. card 0: Intel [HDA Intel], device 0: ALC889A Analog [ALC889A Analog] Subdevices: 1/1 Subdevice #0: subdevice #0 card 0: Intel [HDA Intel], device 1: ALC889A Digital [ALC889A Digital] Subdevices: 1/1 Subdevice #0: subdevice #0 Everything is put to max in alsamixer and nothing is muted (all the sliders are on OO. My speakers do not work, but when I plug in a headphone I hear it very soft. When I connect my stereo and put the sound VERY loud (3-blocks-of-complaining-neighbours loud) I hear it on a normal level but crackling. I added options snd-hda-intel model=mbp5 amixer set IEC958 off to at the end of /etc/modprobe.d/alsa-base.conf. When it's still not working I tried everything here: https://help.ubuntu.com/community/SoundTroubleshooting 1 >>> list-sinks 1 sink(s) available. * index: 0 name: <alsa_output.pci-0000_00_1b.0.analog-stereo> driver: <module-alsa-card.c> flags: HARDWARE HW_MUTE_CTRL HW_VOLUME_CTRL DECIBEL_VOLUME LATENCY DYNAMIC_LATENCY state: SUSPENDED suspend cause: IDLE priority: 9959 volume: 0: 100% 1: 100% 0: 0.00 dB 1: 0.00 dB balance 0.00 base volume: 100% 0.00 dB volume steps: 65537 muted: no current latency: 0.00 ms max request: 0 KiB max rewind: 0 KiB monitor source: 0 sample spec: s16le 2ch 44100Hz channel map: front-left,front-right Stereo used by: 0 linked by: 0 configured latency: 0.00 ms; range is 0.50 .. 371.52 ms card: 0 <alsa_card.pci-0000_00_1b.0> module: 4 properties: alsa.resolution_bits = "16" device.api = "alsa" device.class = "sound" alsa.class = "generic" alsa.subclass = "generic-mix" alsa.name = "ALC889A Analog" alsa.id = "ALC889A Analog" alsa.subdevice = "0" alsa.subdevice_name = "subdevice #0" alsa.device = "0" alsa.card = "0" alsa.card_name = "HDA Intel" alsa.long_card_name = "HDA Intel at 0x9b500000 irq 46" alsa.driver_name = "snd_hda_intel" device.bus_path = "pci-0000:00:1b.0" sysfs.path = "/devices/pci0000:00/0000:00:1b.0/sound/card0" device.bus = "pci" device.vendor.id = "8086" device.vendor.name = "Intel Corporation" device.product.name = "82801H (ICH8 Family) HD Audio Controller" device.form_factor = "internal" device.string = "front:0" device.buffering.buffer_size = "65536" device.buffering.fragment_size = "32768" device.access_mode = "mmap+timer" device.profile.name = "analog-stereo" device.profile.description = "Analog Stereo" device.description = "Built-in Audio Analog Stereo" alsa.mixer_name = "Realtek ALC889A" alsa.components = "HDA:10ec0885,106b3a00,00100103" module-udev-detect.discovered = "1" device.icon_name = "audio-card-pci" ports: analog-output-speaker: Speakers (priority 10000, available: unknown) properties: analog-output-headphones: Headphones (priority 9000, available: no) properties: active port: <analog-output-speaker> 2 and 3: Doesn't seem an permission issue, the sound is very far away (See opening paragraph). 4 thomas@thomas-pc:~$ sudo aplay -l **** List of PLAYBACK Hardware Devices **** Home directory /home/thomas not ours. card 0: Intel [HDA Intel], device 0: ALC889A Analog [ALC889A Analog] Subdevices: 1/1 Subdevice #0: subdevice #0 card 0: Intel [HDA Intel], device 1: ALC889A Digital [ALC889A Digital] Subdevices: 1/1 Subdevice #0: subdevice #0 5 thomas@thomas-pc:~$ find /lib/modules/`uname -r` | grep snd /lib/modules/3.2.0-48-generic/kernel/sound/core/snd-hwdep.ko /lib/modules/3.2.0-48-generic/kernel/sound/core/snd-pcm.ko [.. huge lists continues ..] /lib/modules/3.2.0-48-generic/kernel/sound/pcmcia/pdaudiocf/snd-pdaudiocf.ko /lib/modules/3.2.0-48-generic/kernel/sound/pcmcia/vx/snd-vxpocket.ko thomas@thomas-pc:~$ 6 thomas@thomas-pc:~$ lspci -v | grep -A7 -i "audio" 00:1b.0 Audio device: Intel Corporation 82801H (ICH8 Family) HD Audio Controller (rev 03) Subsystem: Apple Inc. Device 00a4 Flags: bus master, fast devsel, latency 0, IRQ 46 Memory at 9b500000 (64-bit, non-prefetchable) [size=16K] Capabilities: <access denied> Kernel driver in use: snd_hda_intel Kernel modules: snd-hda-intel 7 I guess it's supported. Linux mint and Xubuntu 13.04 had no trouble with sounds. Everything worked out of the box Thanks in advance Edit: alsa-info.sh output: WARNING: /etc/modprobe.d/alsa-base.conf line 45: ignoring bad line starting with 'amixer' ALSA Information Script v 0.4.62 -------------------------------- This script visits the following commands/files to collect diagnostic information about your ALSA installation and sound related hardware. dmesg lspci lsmod aplay amixer alsactl /proc/asound/ /sys/class/sound/ ~/.asoundrc (etc.) See './alsa-info.sh --help' for command line options. WARNING: /etc/modprobe.d/alsa-base.conf line 45: ignoring bad line starting with 'amixer' Automatically upload ALSA information to www.alsa-project.org? [y/N] : y Uploading information to www.alsa-project.org ... Done! Your ALSA information is located at http://www.alsa-project.org/db/?f=6cffc584284d4c0b266eb53249824ef83d6c4e3e Please inform the person helping you. thomas@thomas-pc:~$

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  • Bubble shooter search alghoritm

    - by Fofole
    So I have a Matrix of NxM. At a given position (for ex. [2][5]) I have a value which represents a color. If there is nothing at that point the value is -1. What I need to do is after I add a new point, to check all his neighbours with the same color value and if there are more than 2, set them all to -1. If what I said doesn't make sense what I'm trying to do is an alghoritm which I use to destroy all the same color bubbles from my screen, where the bubbles are memorized in a matrix where -1 means no bubble and {0,1,2,...} represent that there is a bubble with a specific color. This is what I tried and failed: public class Testing { static private int[][] gameMatrix= {{3, 3, 4, 1, 1, 2, 2, 2, 0, 0}, {1, 4, 1, 4, 2, 2, 1, 3, 0, 0}, {2, 2, 4, 4, 3, 1, 2, 4, 0, 0}, {0, 1, 2, 3, 4, 1, 0, 0, 0, 0}, {0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, {0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, }; static int Rows=6; static int Cols=10; static int count; static boolean[][] visited=new boolean[15][15]; static int NOCOLOR = -1; static int color = 1; public static void dfs(int r, int c, int color, boolean set) { for(int dr = -1; dr <= 1; dr++) for(int dc = -1; dc <= 1; dc++) if(!(dr == 0 && dc == 0) && ok(r+dr, c+dc)) { int nr = r+dr; int nc = c+dc; // if it is the same color and we haven't visited this location before if(gameMatrix[nr][nc] == color && !visited[nr][nc]) { visited[nr][nc] = true; count++; dfs(nr, nc, color, set); if(set) { gameMatrix[nr][nc] = NOCOLOR; } } } } static boolean ok(int r, int c) { return r >= 0 && r < Rows && c >= 0 && c < Cols; } static void showMatrix(){ for(int i = 0; i < gameMatrix.length; i++) { System.out.print("["); for(int j = 0; j < gameMatrix[0].length; j++) { System.out.print(" " + gameMatrix[i][j]); } System.out.println(" ]"); } System.out.println(); } static void putValue(int value,int row,int col){ gameMatrix[row][col]=value; } public static void main(String[] args){ System.out.println("Initial Matrix:"); putValue(1, 4, 1); putValue(1, 5, 1); showMatrix(); for(int n = 0; n < 15; n++) for(int m = 0; m < 15; m++) visited[n][m] = false; //reset count count = 0; //dfs(bubbles.get(i).getRow(), bubbles.get(i).getCol(), color, false); // get the contiguous count dfs(5,1,color,false); //if there are more than 2 set the color to NOCOLOR for(int n = 0; n < 15; n++) for(int m = 0; m < 15; m++) visited[n][m] = false; if(count > 2) { //dfs(bubbles.get(i).getRow(), bubbles.get(i).getCol(), color, true); dfs(5,1,color,true); } System.out.println("Matrix after dfs:"); showMatrix(); } }

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  • Using native MySQL driver in Erlang

    - by Mickey Shine
    I am using native MySQL driver (http://code.google.com/p/erlang-mysql-driver/) with mochiweb. When I tried that MySQL driver in shell mode, all woked fine. But when I write some code with Mochiweb, it reported me the following error: =CRASH REPORT==== 4-Jul-2009::04:44:29 === crasher: initial call: mochiweb_socket_server:acceptor_loop/1 pid: <0.61.0> registered_name: [] exception error: no function clause matching mysql:fetch(p1,<<"SELECT * FROM cdb_forums LIMIT 10">>) in function perly_web:loop/2 in call from mochiweb_http:headers/5 ancestors: [perly_web,perly_sup,<0.58.0>] messages: [] links: [<0.60.0>,#Port<0.965>] dictionary: [{mochiweb_request_body,undefined}, {mochiweb_request_qs,[]}, {mochiweb_request_post,[]}, {mochiweb_request_path,"/online"}, {mochiweb_request_cookie, [{"04c_sid","hG9Oyv"}, {"04c_visitedfid","2"}, {"kQx_cookietime","2592000"}, {"kQx_loginuser","admin"}, {"kQx_activationauth", "98b3mdX86fKT9dI4WyKuL61Tqxk%2BW1r6ACpHp9y8itH2xQ"}, {"smile","1D1"}]}] trap_exit: false status: running heap_size: 1597 stack_size: 24 reductions: 5188 neighbours: The code I write in Mochiweb is start(Options) -> {DocRoot, Options1} = get_option(docroot, Options), Loop = fun (Req) -> ?MODULE:loop(Req, DocRoot) end, % we’ll set our maximum to 1 million connections. (default: 2048) mochiweb_http:start([{max, 1000000}, {name, ?MODULE}, {loop, Loop} | Options1]), mysql:start_link(p1, "10.0.0.123", "root", "root", "test"). stop() -> mochiweb_http:stop(?MODULE). loop(Req, DocRoot) -> "/" ++ Path = Req:get(path), case Req:get(method) of Method when Method =:= 'GET'; Method =:= 'HEAD' -> case Path of "online" -> Result1 = mysql:fetch(p1, <<"SELECT * FROM cdb_forums LIMIT 10">>), Body1 = io:format("Result1: ~p~n", [Result1]), Req:ok({"text/plain", Body1}); The connection looks good but when I added Result1 = mysql:fetch(p1, <<"SELECT * FROM cdb_forums LIMIT 10">>), it crashed. Can someone help me? Thanks in advance~ //================================================== updated: I noticed the follwoing information. If that is correct? =PROGRESS REPORT==== 4-Jul-2009::05:49:32 === supervisor: {local,kernel_safe_sup} started: [{pid,<0.65.0>}, {name,inet_gethost_native_sup}, {mfa,{inet_gethost_native,start_link,[]}}, {restart_type,temporary}, {shutdown,1000}, {child_type,worker}] mysql_conn: greeting version "5.1.33-log" (protocol 10) salt "ne0_m'vA" caps 63487 serverchar <<8,2,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0>> salt2 "!|o;vabJ*4bt" mysql_auth send packet 1: <<5,162,0,0,64,66,15,0,8,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,114,111,111,116,0,20,52,235,78, 173,36,251,201,242,172,139,113,231,253,181,245,3, 91,198,111,135>> Link: {ok,<0.62.0>} =SUPERVISOR REPORT==== 4-Jul-2009::05:49:32 === Supervisor: {local,perly_sup} Context: start_error Reason: ok Offender: [{pid,undefined}, {name,perly_web}, {mfa, {perly_web,start, [[{ip,"0.0.0.0"}, {port,8000}, {docroot, "/work/mochiweb-read-only/scripts/perly/priv/www"}]]}}, {restart_type,permanent}, {shutdown,5000}, {child_type,worker}]

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  • Sorted sets and comparators

    - by Jack
    Hello, I'm working with a TreeSetthat is meant to store pathfind locations used during the execution of a A* algorithm. Basically until there are "open" elements (still to be exhaustively visited) the neighbours of every open element are taken into consideration and added to a SortedSetthat keeps them ordered by their cost and heuristic cost. This means that I have a class like: public class PathTileInfo implements Comparable<PathTileInfo> { int cost; int hCost; final int x, y; @Override public int compareTo(PathTileInfo t2) { int c = cost + hCost; int c2 = t2.cost + t2.hCost; int costComp = c < c2 ? -1 : (c > c2 ? 1: 0); return costComp != 0 ? costComp : (x < t2.x || y < t2.y ? -1 : (x > t2.x || y > t2.y ? 1 : 0)); } @Override public boolean equals(Object o2) { if (o2 instanceof PathTileInfo) { PathTileInfo i = (PathTileInfo)o2; return i.cost + i.hCost == cost + hCost && x == i.x && y == i.y; } return false; } } In this way first the total cost is considered, then, since a total ordering is needed (consistency with equals) a ordering according to the x,y coordinate is taken into account. This should work but simply it doesn't, if I iterate over the TreeSet during the algorithm execution like in for (PathTileInfo t : openSet) System.out.print("("+t.x+","+t.y+","+(t.cost+t.hCost)+") "); I get results in which the right ordering is not kept, eg: (7,7,6) (7,6,7) (6,8,6) (6,6,7) (5,8,7) (5,7,7) (6,7,6) (6,6,7) (6,5,7) (5,7,7) (5,5,8) (4,7,7) (4,6,8) (4,5,8) is there something subtle I am missing? Thanks!

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  • Python/numpy tricky slicing problem

    - by daver
    Hi stack overflow, I have a problem with some numpy stuff. I need a numpy array to behave in an unusual manner by returning a slice as a view of the data I have sliced, not a copy. So heres an example of what I want to do: Say we have a simple array like this: a = array([1, 0, 0, 0]) I would like to update consecutive entries in the array (moving left to right) with the previous entry from the array, using syntax like this: a[1:] = a[0:3] This would get the following result: a = array([1, 1, 1, 1]) Or something like this: a[1:] = 2*a[:3] # a = [1,2,4,8] To illustrate further I want the following kind of behaviour: for i in range(len(a)): if i == 0 or i+1 == len(a): continue a[i+1] = a[i] Except I want the speed of numpy. The default behavior of numpy is to take a copy of the slice, so what I actually get is this: a = array([1, 1, 0, 0]) I already have this array as a subclass of the ndarray, so I can make further changes to it if need be, I just need the slice on the right hand side to be continually updated as it updates the slice on the left hand side. Am I dreaming or is this magic possible? Update: This is all because I am trying to use Gauss-Seidel iteration to solve a linear algebra problem, more or less. It is a special case involving harmonic functions, I was trying to avoid going into this because its really not necessary and likely to confuse things further, but here goes. The algorithm is this: while not converged: for i in range(len(u[:,0])): for j in range(len(u[0,:])): # skip over boundary entries, i,j == 0 or len(u) u[i,j] = 0.25*(u[i-1,j] + u[i+1,j] + u[i, j-1] + u[i,j+1]) Right? But you can do this two ways, Jacobi involves updating each element with its neighbours without considering updates you have already made until the while loop cycles, to do it in loops you would copy the array then update one array from the copied array. However Gauss-Seidel uses information you have already updated for each of the i-1 and j-1 entries, thus no need for a copy, the loop should essentially 'know' since the array has been re-evaluated after each single element update. That is to say, every time we call up an entry like u[i-1,j] or u[i,j-1] the information calculated in the previous loop will be there. I want to replace this slow and ugly nested loop situation with one nice clean line of code using numpy slicing: u[1:-1,1:-1] = 0.25(u[:-2,1:-1] + u[2:,1:-1] + u[1:-1,:-2] + u[1:-1,2:]) But the result is Jacobi iteration because when you take a slice: u[:,-2,1:-1] you copy the data, thus the slice is not aware of any updates made. Now numpy still loops right? Its not parallel its just a faster way to loop that looks like a parallel operation in python. I want to exploit this behaviour by sort of hacking numpy to return a pointer instead of a copy when I take a slice. Right? Then every time numpy loops, that slice will 'update' or really just replicate whatever happened in the update. To do this I need slices on both sides of the array to be pointers. Anyway if there is some really really clever person out there that awesome, but I've pretty much resigned myself to believing the only answer is to loop in C.

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  • Explain the Peak and Flag Algorithm

    - by Isaac Levin
    EDIT Just was pointed that the requirements state peaks cannot be ends of Arrays. So I ran across this site http://codility.com/ Which gives you programming problems and gives you certificates if you can solve them in 2 hours. The very first question is one I have seen before, typically called the Peaks and Flags question. If you are not familiar A non-empty zero-indexed array A consisting of N integers is given. A peak is an array element which is larger than its neighbours. More precisely, it is an index P such that 0 < P < N - 1 and A[P - 1] < A[P] A[P + 1] . For example, the following array A: A[0] = 1 A[1] = 5 A[2] = 3 A[3] = 4 A[4] = 3 A[5] = 4 A[6] = 1 A[7] = 2 A[8] = 3 A[9] = 4 A[10] = 6 A[11] = 2 has exactly four peaks: elements 1, 3, 5 and 10. You are going on a trip to a range of mountains whose relative heights are represented by array A. You have to choose how many flags you should take with you. The goal is to set the maximum number of flags on the peaks, according to certain rules. Flags can only be set on peaks. What's more, if you take K flags, then the distance between any two flags should be greater than or equal to K. The distance between indices P and Q is the absolute value |P - Q|. For example, given the mountain range represented by array A, above, with N = 12, if you take: two flags, you can set them on peaks 1 and 5; three flags, you can set them on peaks 1, 5 and 10; four flags, you can set only three flags, on peaks 1, 5 and 10. You can therefore set a maximum of three flags in this case. Write a function that, given a non-empty zero-indexed array A of N integers, returns the maximum number of flags that can be set on the peaks of the array. For example, given the array above the function should return 3, as explained above. Assume that: N is an integer within the range [1..100,000]; each element of array A is an integer within the range [0..1,000,000,000]. Complexity: expected worst-case time complexity is O(N); expected worst-case space complexity is O(N), beyond input storage (not counting the storage required for input arguments). Elements of input arrays can be modified. So this makes sense, but I failed it using this code public int GetFlags(int[] A) { List<int> peakList = new List<int>(); for (int i = 0; i <= A.Length - 1; i++) { if ((A[i] > A[i + 1] && A[i] > A[i - 1])) { peakList.Add(i); } } List<int> flagList = new List<int>(); int distance = peakList.Count; flagList.Add(peakList[0]); for (int i = 1, j = 0, max = peakList.Count; i < max; i++) { if (Math.Abs(Convert.ToDecimal(peakList[j]) - Convert.ToDecimal(peakList[i])) >= distance) { flagList.Add(peakList[i]); j = i; } } return flagList.Count; } EDIT int[] A = new int[] { 7, 10, 4, 5, 7, 4, 6, 1, 4, 3, 3, 7 }; The correct answer is 3, but my application says 2 This I do not get, since there are 4 peaks (indices 1,4,6,8) and from that, you should be able to place a flag at 2 of the peaks (1 and 6) Am I missing something here? Obviously my assumption is that the beginning or end of an Array can be a peak, is this not the case? If this needs to go in Stack Exchange Programmers, I will move it, but thought dialog here would be helpful. EDIT

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  • how to speed up the code??

    - by kaushik
    i have very huge code about 600 lines plus. cant post the whole thing here. but a particular code snippet is taking so much time,leading to problems. here i post that part of code please tell me what to do speed up the processing.. please suggest the part which may be the reason and measure to improve them if this small part of code is understandable. using_data={} def join_cost(a , b): global using_data #print a #print b save_a=[] save_b=[] print 1 #for i in range(len(m)): #if str(m[i][0])==str(a): save_a=database_index[a] #for i in range(len(m)): # if str(m[i][0])==str(b): #print 'save_a',save_a #print 'save_b',save_b print 2 save_b=database_index[b] using_data[save_a[0]]=save_a s=str(save_a[1]).replace('phone','text') s=str(s)+'.pm' p=os.path.join("c:/begpython/wavnk/",s) x=open(p , 'r') print 3 for i in range(6): x.readline() k2='a' j=0 o=[] while k2 is not '': k2=x.readline() k2=k2.rstrip('\n') oj=k2.split(' ') o=o+[oj] #print o[j] j=j+1 #print j #print o[2][0] temp=long(1232332) end_time=save_a[4] #print end_time k=(j-1) for i in range(k): diff=float(o[i][0])-float(end_time) if diff<0: diff=diff*(-1) if temp>diff: temp=diff pm_row=i #print pm_row #print temp #print o[pm_row] #pm_row=3 q=[] print 4 l=str(p).replace('.pm','.mcep') z=open(l ,'r') for i in range(pm_row): z.readline() k3=z.readline() k3=k3.rstrip('\n') q=k3.split(' ') #print q print 5 s=str(save_b[1]).replace('phone','text') s=str(s)+'.pm' p=os.path.join("c:/begpython/wavnk/",s) x=open(p , 'r') for i in range(6): x.readline() k2='a' j=0 o=[] while k2 is not '': k2=x.readline() k2=k2.rstrip('\n') oj=k2.split(' ') o=o+[oj] #print o[j] j=j+1 #print j #print o[2][0] temp=long(1232332) strt_time=save_b[3] #print strt_time k=(j-1) for i in range(k): diff=float(o[i][0])-float(strt_time) if diff<0: diff=diff*(-1) if temp>diff: temp=diff pm_row=i #print pm_row #print temp #print o[pm_row] #pm_row=3 w=[] l=str(p).replace('.pm','.mcep') z=open(l ,'r') for i in range(pm_row): z.readline() k3=z.readline() k3=k3.rstrip('\n') w=k3.split(' ') #print w cost=0 for i in range(12): #print q[i] #print w[i] h=float(q[i])-float(w[i]) cost=cost+math.pow(h,2) j_cost=math.sqrt(cost) #print cost return j_cost def target_cost(a , b): a=(b+1)*3 b=(a+1)*2 t_cost=(a+b)*5/2 return t_cost r1='shht:ra_77' r2='grx_18' g=[] nodes=[] nodes=nodes+[[r1]] for i in range(len(y_in_db_format)): g=y_in_db_format[i] #print g #print g[0] g.remove(str(g[0])) nodes=nodes+[g] nodes=nodes+[[r2]] print nodes print "lenght of nodes",len(nodes) lists=[] #lists=lists+[r1] for i in range(len(nodes)): for j in range(len(nodes[i])): lists=lists+[nodes[i][j]] #lists=lists+[r2] print lists distance={} for i in range(len(lists)): if i==0: distance[str(lists[i])]=0 else: distance[str(lists[i])]=long(123231223) #print distance group_dist=[] infinity=long(123232323) for i in range(len(nodes)): distances=[] for j in range(len(nodes[i])): #distances=[] if i==0: distances=distances+[[nodes[i][j], 0]] else: distances=distances+[[nodes[i][j],infinity]] group_dist=group_dist+[distances] #print distances print "group_distances",group_dist #print "check",group_dist[0][0][1] #costs={} #for i in range(len(lists)): #if i==0: # costs[str(lists[i])]=1 #else: # costs[str(lists[i])]=get_selfcost(lists[i]) path=[] for i in range(len(nodes)): mini=[] if i!=(len(nodes)-1): #temp=long(123234324) #Now calculate the cost between the current node and each of its neighbour for k in range(len(nodes[(i+1)])): for j in range(len(nodes[i])): current=nodes[i][j] #print "current_node",current j_distance=join_cost( current , nodes[i+1][k]) #t_distance=target_cost( current , nodes[i+1][k]) t_distance=34 #print distance #print "distance between current and neighbours",distance total_distance=(.5*(float(group_dist[i][j][1])+float(j_distance))+.5*(float(t_distance))) #print "total distance between the intial_nodes and current neighbour",total_distance if int(group_dist[i+1][k][1]) > int(total_distance): group_dist[i+1][k][1]=total_distance #print "updated distance",group_dist[i+1][k][1] a=current #print "the neighbour",nodes[i+1][k],"updated the value",a mini=mini+[[str(nodes[i+1][k]),a]] print mini

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