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  • How I understood monads, part 1/2: sleepless and self-loathing in Seattle

    - by Bertrand Le Roy
    For some time now, I had been noticing some interest for monads, mostly in the form of unintelligible (to me) blog posts and comments saying “oh, yeah, that’s a monad” about random stuff as if it were absolutely obvious and if I didn’t know what they were talking about, I was probably an uneducated idiot, ignorant about the simplest and most fundamental concepts of functional programming. Fair enough, I am pretty much exactly that. Being the kind of guy who can spend eight years in college just to understand a few interesting concepts about the universe, I had to check it out and try to understand monads so that I too can say “oh, yeah, that’s a monad”. Man, was I hit hard in the face with the limitations of my own abstract thinking abilities. All the articles I could find about the subject seemed to be vaguely understandable at first but very quickly overloaded the very few concept slots I have available in my brain. They also seemed to be consistently using arcane notation that I was entirely unfamiliar with. It finally all clicked together one Friday afternoon during the team’s beer symposium when Louis was patient enough to break it down for me in a language I could understand (C#). I don’t know if being intoxicated helped. Feel free to read this with or without a drink in hand. So here it is in a nutshell: a monad allows you to manipulate stuff in interesting ways. Oh, OK, you might say. Yeah. Exactly. Let’s start with a trivial case: public static class Trivial { public static TResult Execute<T, TResult>( this T argument, Func<T, TResult> operation) { return operation(argument); } } This is not a monad. I removed most concepts here to start with something very simple. There is only one concept here: the idea of executing an operation on an object. This is of course trivial and it would actually be simpler to just apply that operation directly on the object. But please bear with me, this is our first baby step. Here’s how you use that thing: "some string" .Execute(s => s + " processed by trivial proto-monad.") .Execute(s => s + " And it's chainable!"); What we’re doing here is analogous to having an assembly chain in a factory: you can feed it raw material (the string here) and a number of machines that each implement a step in the manufacturing process and you can start building stuff. The Trivial class here represents the empty assembly chain, the conveyor belt if you will, but it doesn’t care what kind of raw material gets in, what gets out or what each machine is doing. It is pure process. A real monad will need a couple of additional concepts. Let’s say the conveyor belt needs the material to be processed to be contained in standardized boxes, just so that it can safely and efficiently be transported from machine to machine or so that tracking information can be attached to it. Each machine knows how to treat raw material or partly processed material, but it doesn’t know how to treat the boxes so the conveyor belt will have to extract the material from the box before feeding it into each machine, and it will have to box it back afterwards. This conveyor belt with boxes is essentially what a monad is. It has one method to box stuff, one to extract stuff from its box and one to feed stuff into a machine. So let’s reformulate the previous example but this time with the boxes, which will do nothing for the moment except containing stuff. public class Identity<T> { public Identity(T value) { Value = value; } public T Value { get; private set;} public static Identity<T> Unit(T value) { return new Identity<T>(value); } public static Identity<U> Bind<U>( Identity<T> argument, Func<T, Identity<U>> operation) { return operation(argument.Value); } } Now this is a true to the definition Monad, including the weird naming of the methods. It is the simplest monad, called the identity monad and of course it does nothing useful. Here’s how you use it: Identity<string>.Bind( Identity<string>.Unit("some string"), s => Identity<string>.Unit( s + " was processed by identity monad.")).Value That of course is seriously ugly. Note that the operation is responsible for re-boxing its result. That is a part of strict monads that I don’t quite get and I’ll take the liberty to lift that strange constraint in the next examples. To make this more readable and easier to use, let’s build a few extension methods: public static class IdentityExtensions { public static Identity<T> ToIdentity<T>(this T value) { return new Identity<T>(value); } public static Identity<U> Bind<T, U>( this Identity<T> argument, Func<T, U> operation) { return operation(argument.Value).ToIdentity(); } } With those, we can rewrite our code as follows: "some string".ToIdentity() .Bind(s => s + " was processed by monad extensions.") .Bind(s => s + " And it's chainable...") .Value; This is considerably simpler but still retains the qualities of a monad. But it is still pointless. Let’s look at a more useful example, the state monad, which is basically a monad where the boxes have a label. It’s useful to perform operations on arbitrary objects that have been enriched with an attached state object. public class Stateful<TValue, TState> { public Stateful(TValue value, TState state) { Value = value; State = state; } public TValue Value { get; private set; } public TState State { get; set; } } public static class StateExtensions { public static Stateful<TValue, TState> ToStateful<TValue, TState>( this TValue value, TState state) { return new Stateful<TValue, TState>(value, state); } public static Stateful<TResult, TState> Execute<TValue, TState, TResult>( this Stateful<TValue, TState> argument, Func<TValue, TResult> operation) { return operation(argument.Value) .ToStateful(argument.State); } } You can get a stateful version of any object by calling the ToStateful extension method, passing the state object in. You can then execute ordinary operations on the values while retaining the state: var statefulInt = 3.ToStateful("This is the state"); var processedStatefulInt = statefulInt .Execute(i => ++i) .Execute(i => i * 10) .Execute(i => i + 2); Console.WriteLine("Value: {0}; state: {1}", processedStatefulInt.Value, processedStatefulInt.State); This monad differs from the identity by enriching the boxes. There is another way to give value to the monad, which is to enrich the processing. An example of that is the writer monad, which can be typically used to log the operations that are being performed by the monad. Of course, the richest monads enrich both the boxes and the processing. That’s all for today. I hope with this you won’t have to go through the same process that I did to understand monads and that you haven’t gone into concept overload like I did. Next time, we’ll examine some examples that you already know but we will shine the monadic light, hopefully illuminating them in a whole new way. Realizing that this pattern is actually in many places but mostly unnoticed is what will enable the truly casual “oh, yes, that’s a monad” comments. Here’s the code for this article: http://weblogs.asp.net/blogs/bleroy/Samples/Monads.zip The Wikipedia article on monads: http://en.wikipedia.org/wiki/Monads_in_functional_programming This article was invaluable for me in understanding how to express the canonical monads in C# (interesting Linq stuff in there): http://blogs.msdn.com/b/wesdyer/archive/2008/01/11/the-marvels-of-monads.aspx

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  • Drivers for NVIDIA 520M not working in Ubuntu 12.04

    - by Don
    I am aware that this is nominally a duplicate question, however I've read the other questions and haven't been able to resolve my problem after many hours and attempts, so please don't delete it. Additionally, it seems like many answers to the other questions are specifically dependent on certain situations. My situation being different from the others I found represented, here's my question. Until last night, I had Ubuntu 12.04 installed with Wubi, and it ran ok, though slowly and with occasional hangs. So I partitioned the drive and installed 12.04 in its own partition. Now when I start it, I am stuck using 2D. I believe this is an NVIDIA bug. My NVIDIA card is a GT 520M and my machine has Optimus. Additional Drivers only displays my wireless driver. Going to System Settings Details Graphics shows Driver:Unknown, Experience:Standard. I downloaded the driver from the NVIDIA website, and ran the installer with no errors, except that the "distribution-provided pre-install script failed". After rebooting, my screen was stuck at 640X480, which was fixed by editing /etc/X11/xorg.conf However, I still was stuck in 2D, and nothing else had changed either. A thread suggested something called Bumblebee. I tried that, and when I ran optirun firefoxI got a frozen blank screen. Following another suggestion, I checked the BIOS to try and disable Optimus. I found and ran myriad other commands to try and fix the problem and nothing changed. Now I have just done a clean re-install of Ubuntu. From there, I: Installed all the updates Downloaded the NVIDIA driver Installed it Got screen stuck at 640X480, fixed in xorg.conf. To recap the problem: I can't get the NVIDIA drivers working I am stuck using 2D I'm an idiot I think if the first one is solved, the solution to the second will naturally follow. If you need me to provide any other information, I'd be happy to. From what I've seen in other threads, I think this information may help: lsmod: dh@donsMachine:~$ lsmod Module Size Used by nvidia 12353161 0 snd_hda_codec_hdmi 32474 1 snd_hda_codec_realtek 223867 1 joydev 17693 0 parport_pc 32866 0 ppdev 17113 0 rfcomm 47604 0 bnep 18281 2 bluetooth 180104 10 rfcomm,bnep snd_hda_intel 33773 3 snd_hda_codec 127706 3 snd_hda_codec_hdmi,snd_hda_codec_realtek,snd_hda_intel snd_hwdep 13668 1 snd_hda_codec snd_pcm 97188 3 snd_hda_codec_hdmi,snd_hda_intel,snd_hda_codec uvcvideo 72627 0 videodev 98259 1 uvcvideo v4l2_compat_ioctl32 17128 1 videodev snd_seq_midi 13324 0 snd_rawmidi 30748 1 snd_seq_midi snd_seq_midi_event 14899 1 snd_seq_midi snd_seq 61896 2 snd_seq_midi,snd_seq_midi_event lib80211_crypt_tkip 17390 0 wl 2568210 0 lib80211 14381 2 lib80211_crypt_tkip,wl snd_timer 29990 2 snd_pcm,snd_seq snd_seq_device 14540 3 snd_seq_midi,snd_rawmidi,snd_seq snd 78855 16 snd_hda_codec_hdmi,snd_hda_codec_realtek,snd_hda_intel,snd_hda_codec,snd_hwdep,snd_pcm,snd_rawmidi,snd_seq,snd_timer,snd_seq_device psmouse 87692 0 serio_raw 13211 0 i915 468745 2 soundcore 15091 1 snd snd_page_alloc 18529 2 snd_hda_intel,snd_pcm drm_kms_helper 46978 1 i915 drm 242038 3 i915,drm_kms_helper mei 41616 0 i2c_algo_bit 13423 1 i915 mxm_wmi 12979 0 acer_wmi 28418 0 sparse_keymap 13890 1 acer_wmi video 19596 1 i915 wmi 19256 2 mxm_wmi,acer_wmi mac_hid 13253 0 lp 17799 0 parport 46562 3 parport_pc,ppdev,lp tg3 152032 0 sdhci_pci 18826 0 sdhci 33205 1 sdhci_pci lspci -nn | grep VGA dh@donsMachine:~$ lspci -nn | grep VGA 00:02.0 VGA compatible controller [0300]: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller [8086:0116] (rev 09) 01:00.0 VGA compatible controller [0300]: NVIDIA Corporation Device [10de:0df7] (rev a1) lshw dh@donsMachine:~$ sudo lshw [sudo] password for dh: donsmachine description: Notebook product: EasyNote TS44HR () vendor: Packard Bell version: V1.12 serial: LXBWZ02017134209D71601 width: 64 bits capabilities: smbios-2.7 dmi-2.7 vsyscall32 configuration: boot=normal chassis=notebook uuid=16FE576B-CA15-11E0-B096-B870F4E51243 *-core description: Motherboard product: SJV50_HR vendor: Packard Bell physical id: 0 version: Base Board Version serial: Base Board Serial Number slot: Base Board Chassis Location *-firmware description: BIOS vendor: Packard Bell physical id: 0 version: V1.12 date: 07/11/2011 size: 1MiB capacity: 2496KiB capabilities: pci upgrade shadowing cdboot bootselect edd int13floppynec int13floppytoshiba int13floppy360 int13floppy1200 int13floppy720 int13floppy2880 int9keyboard int10video acpi usb biosbootspecification *-memory description: System Memory physical id: 1b slot: System board or motherboard size: 4GiB *-bank:0 description: SODIMM DDR3 Synchronous 1333 MHz (0.8 ns) product: NT2GC64B88B0NS-CG vendor: Nanya Technology physical id: 0 serial: 598E126E slot: ChannelA-DIMM0 size: 2GiB width: 64 bits clock: 1333MHz (0.8ns) *-bank:1 description: DIMM [empty] physical id: 1 slot: ChannelA-DIMM1 *-bank:2 description: SODIMM DDR3 Synchronous 1333 MHz (0.8 ns) product: NT2GC64B88B0NS-CG vendor: Nanya Technology physical id: 2 serial: 159E126C slot: ChannelB-DIMM0 size: 2GiB width: 64 bits clock: 1333MHz (0.8ns) *-bank:3 description: DIMM [empty] physical id: 3 slot: ChannelB-DIMM1 *-cpu description: CPU product: Intel(R) Core(TM) i3-2330M CPU @ 2.20GHz vendor: Intel Corp. physical id: 2e bus info: cpu@0 version: Intel(R) Core(TM) i3-2330M CPU @ 2.20GHz slot: CPU1 size: 2GHz capacity: 4GHz width: 64 bits clock: 1333MHz capabilities: x86-64 fpu fpu_exception wp vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx rdtscp constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic popcnt tsc_deadline_timer xsave avx lahf_lm arat epb xsaveopt pln pts tpr_shadow vnmi flexpriority ept vpid cpufreq configuration: cores=2 enabledcores=2 threads=4 *-cache:0 description: L1 cache physical id: 30 slot: L1 Cache size: 32KiB capacity: 32KiB capabilities: synchronous internal write-through instruction *-cache:1 description: L2 cache physical id: 31 slot: L2 Cache size: 256KiB capacity: 256KiB capabilities: synchronous internal write-through unified *-cache:2 description: L3 cache physical id: 32 slot: L3 Cache size: 3MiB capacity: 3MiB capabilities: synchronous internal write-through unified *-cache description: L1 cache physical id: 2f slot: L1 Cache size: 32KiB capacity: 32KiB capabilities: synchronous internal write-through data *-pci description: Host bridge product: 2nd Generation Core Processor Family DRAM Controller vendor: Intel Corporation physical id: 100 bus info: pci@0000:00:00.0 version: 09 width: 32 bits clock: 33MHz configuration: driver=agpgart-intel resources: irq:0 *-pci:0 description: PCI bridge product: Xeon E3-1200/2nd Generation Core Processor Family PCI Express Root Port vendor: Intel Corporation physical id: 1 bus info: pci@0000:00:01.0 version: 09 width: 32 bits clock: 33MHz capabilities: pci pm msi pciexpress normal_decode bus_master cap_list configuration: driver=pcieport resources: irq:40 ioport:2000(size=4096) memory:d0000000-d10fffff ioport:a0000000(size=301989888) *-display description: VGA compatible controller product: NVIDIA Corporation vendor: NVIDIA Corporation physical id: 0 bus info: pci@0000:01:00.0 version: a1 width: 64 bits clock: 33MHz capabilities: pm msi pciexpress vga_controller bus_master cap_list rom configuration: driver=nvidia latency=0 resources: irq:16 memory:d0000000-d0ffffff memory:a0000000-afffffff memory:b0000000-b1ffffff ioport:2000(size=128) memory:d1000000-d107ffff *-display description: VGA compatible controller product: 2nd Generation Core Processor Family Integrated Graphics Controller vendor: Intel Corporation physical id: 2 bus info: pci@0000:00:02.0 version: 09 width: 64 bits clock: 33MHz capabilities: msi pm vga_controller bus_master cap_list rom configuration: driver=i915 latency=0 resources: irq:43 memory:d1400000-d17fffff memory:c0000000-cfffffff ioport:3000(size=64) *-communication description: Communication controller product: 6 Series/C200 Series Chipset Family MEI Controller #1 vendor: Intel Corporation physical id: 16 bus info: pci@0000:00:16.0 version: 04 width: 64 bits clock: 33MHz capabilities: pm msi bus_master cap_list configuration: driver=mei latency=0 resources: irq:42 memory:d1a04000-d1a0400f *-usb:0 description: USB controller product: 6 Series/C200 Series Chipset Family USB Enhanced Host Controller #2 vendor: Intel Corporation physical id: 1a bus info: pci@0000:00:1a.0 version: 04 width: 32 bits clock: 33MHz capabilities: pm debug ehci bus_master cap_list configuration: driver=ehci_hcd latency=0 resources: irq:16 memory:d1a0a000-d1a0a3ff *-multimedia description: Audio device product: 6 Series/C200 Series Chipset Family High Definition Audio Controller vendor: Intel Corporation physical id: 1b bus info: pci@0000:00:1b.0 version: 04 width: 64 bits clock: 33MHz capabilities: pm msi pciexpress bus_master cap_list configuration: driver=snd_hda_intel latency=0 resources: irq:44 memory:d1a00000-d1a03fff *-pci:1 description: PCI bridge product: 6 Series/C200 Series Chipset Family PCI Express Root Port 1 vendor: Intel Corporation physical id: 1c bus info: pci@0000:00:1c.0 version: b4 width: 32 bits clock: 33MHz capabilities: pci pciexpress msi pm normal_decode bus_master cap_list configuration: driver=pcieport resources: irq:17 memory:9fb00000-9fbfffff ioport:d1800000(size=1048576) *-network description: Ethernet interface product: NetLink BCM57785 Gigabit Ethernet PCIe vendor: Broadcom Corporation physical id: 0 bus info: pci@0000:02:00.0 logical name: eth0 version: 10 serial: b8:70:f4:e5:12:43 capacity: 1Gbit/s width: 64 bits clock: 33MHz capabilities: pm msi msix pciexpress bus_master cap_list rom ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation configuration: autonegotiation=on broadcast=yes driver=tg3 driverversion=3.121 firmware=sb latency=0 link=no multicast=yes port=twisted pair resources: irq:16 memory:d1830000-d183ffff memory:d1840000-d184ffff memory:d1850000-d18507ff *-generic:0 description: SD Host controller product: NetXtreme BCM57765 Memory Card Reader vendor: Broadcom Corporation physical id: 0.1 bus info: pci@0000:02:00.1 version: 10 width: 64 bits clock: 33MHz capabilities: pm msi pciexpress bus_master cap_list configuration: driver=sdhci-pci latency=0 resources: irq:17 memory:d1800000-d180ffff *-generic:1 UNCLAIMED description: System peripheral product: Broadcom Corporation vendor: Broadcom Corporation physical id: 0.2 bus info: pci@0000:02:00.2 version: 10 width: 64 bits clock: 33MHz capabilities: pm msi pciexpress bus_master cap_list configuration: latency=0 resources: memory:d1810000-d181ffff *-generic:2 UNCLAIMED description: System peripheral product: Broadcom Corporation vendor: Broadcom Corporation physical id: 0.3 bus info: pci@0000:02:00.3 version: 10 width: 64 bits clock: 33MHz capabilities: pm msi pciexpress bus_master cap_list configuration: latency=0 resources: memory:d1820000-d182ffff *-pci:2 description: PCI bridge product: 6 Series/C200 Series Chipset Family PCI Express Root Port 2 vendor: Intel Corporation physical id: 1c.1 bus info: pci@0000:00:1c.1 version: b4 width: 32 bits clock: 33MHz capabilities: pci pciexpress msi pm normal_decode bus_master cap_list configuration: driver=pcieport resources: irq:16 memory:d1900000-d19fffff *-network description: Wireless interface product: BCM43225 802.11b/g/n vendor: Broadcom Corporation physical id: 0 bus info: pci@0000:03:00.0 logical name: eth1 version: 01 serial: 68:a3:c4:44:81:96 width: 64 bits clock: 33MHz capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless configuration: broadcast=yes driver=wl0 driverversion=5.100.82.38 ip=192.168.0.12 latency=0 multicast=yes wireless=IEEE 802.11bgn resources: irq:17 memory:d1900000-d1903fff *-usb:1 description: USB controller product: 6 Series/C200 Series Chipset Family USB Enhanced Host Controller #1 vendor: Intel Corporation physical id: 1d bus info: pci@0000:00:1d.0 version: 04 width: 32 bits clock: 33MHz capabilities: pm debug ehci bus_master cap_list configuration: driver=ehci_hcd latency=0 resources: irq:23 memory:d1a09000-d1a093ff *-isa description: ISA bridge product: HM65 Express Chipset Family LPC Controller vendor: Intel Corporation physical id: 1f bus info: pci@0000:00:1f.0 version: 04 width: 32 bits clock: 33MHz capabilities: isa bus_master cap_list configuration: latency=0 *-storage description: SATA controller product: 6 Series/C200 Series Chipset Family 6 port SATA AHCI Controller vendor: Intel Corporation physical id: 1f.2 bus info: pci@0000:00:1f.2 logical name: scsi0 logical name: scsi1 version: 04 width: 32 bits clock: 66MHz capabilities: storage msi pm ahci_1.0 bus_master cap_list emulated configuration: driver=ahci latency=0 resources: irq:41 ioport:3098(size=8) ioport:30bc(size=4) ioport:3090(size=8) ioport:30b8(size=4) ioport:3060(size=32) memory:d1a08000-d1a087ff *-disk description: ATA Disk product: ST9500325AS vendor: Seagate physical id: 0 bus info: scsi@0:0.0.0 logical name: /dev/sda version: 0001 serial: S2W1AMSX size: 465GiB (500GB) capabilities: partitioned partitioned:dos configuration: ansiversion=5 signature=a45f21e9 *-volume:0 description: Windows NTFS volume physical id: 1 bus info: scsi@0:0.0.0,1 logical name: /dev/sda1 version: 3.1 serial: 46aa-2a25 size: 19GiB capacity: 20GiB capabilities: primary ntfs initialized configuration: clustersize=4096 created=2011-08-25 21:32:00 filesystem=ntfs label=PQSERVICE state=clean *-volume:1 description: Windows NTFS volume physical id: 2 bus info: scsi@0:0.0.0,2 logical name: /dev/sda2 version: 3.1 serial: 10aa-ad1a size: 98MiB capacity: 100MiB capabilities: primary bootable ntfs initialized configuration: clustersize=4096 created=2011-08-25 21:32:03 filesystem=ntfs label=SYSTEM RESERVED state=clean *-volume:2 description: Windows NTFS volume physical id: 3 bus info: scsi@0:0.0.0,3 logical name: /dev/sda3 version: 3.1 serial: 668c5afc-182e-ff4b-b084-3cc09f54972d size: 395GiB capacity: 395GiB capabilities: primary ntfs initialized configuration: clustersize=4096 created=2011-08-25 21:32:03 filesystem=ntfs label=Don's Machine state=clean *-volume:3 description: Extended partition physical id: 4 bus info: scsi@0:0.0.0,4 logical name: /dev/sda4 size: 49GiB capacity: 49GiB capabilities: primary extended partitioned partitioned:extended *-logicalvolume:0 description: Linux swap / Solaris partition physical id: 5 logical name: /dev/sda5 capacity: 3945MiB capabilities: nofs *-logicalvolume:1 description: Linux filesystem partition physical id: 6 logical name: /dev/sda6 logical name: / capacity: 46GiB configuration: mount.fstype=ext4 mount.options=rw,relatime,errors=remount-ro,user_xattr,barrier=1,data=ordered state=mounted *-cdrom description: DVD-RAM writer product: DVD-RW DVRTD11RS vendor: PIONEER physical id: 1 bus info: scsi@1:0.0.0 logical name: /dev/cdrom logical name: /dev/cdrw logical name: /dev/dvd logical name: /dev/dvdrw logical name: /dev/sr0 version: 1.01 capabilities: removable audio cd-r cd-rw dvd dvd-r dvd-ram configuration: ansiversion=5 status=nodisc *-serial UNCLAIMED description: SMBus product: 6 Series/C200 Series Chipset Family SMBus Controller vendor: Intel Corporation physical id: 1f.3 bus info: pci@0000:00:1f.3 version: 04 width: 64 bits clock: 33MHz configuration: latency=0 resources: memory:d1a06000-d1a060ff ioport:3040(size=32) *-power UNCLAIMED description: OEM_Define1 product: OEM_Define5 vendor: OEM_Define2 physical id: 1 version: OEM_Define6 serial: OEM_Define3 capacity: 75mWh *-battery description: Lithium Ion Battery product: CRB Battery 0 vendor: -Virtual Battery 0- physical id: 2 version: 10/12/2007 serial: Battery 0 slot: Fake

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  • Our winners- and some BBQ for everyone

    - by Steve Tunstall
    Congrats to our two winners for the first two comments on my last entry. Steve from Australia and John Lemon. Steve won since he was the first person over the International Date Line to see the post I made so late after a workday on Friday. So not only does he get to live in a country with the 2nd most beautiful women in the world, but now he gets some cool Oracle Swag, too. (Yes, I live on the beach in southern California, so you can guess where 1st place is for that other contest…Now if Steve happens to live in Manly, we may actually have a tie going…) OK, ok, for everyone else, you can be winners, too. How you ask? I will make you the envy of every guy and gal in your neighborhood or campsite. What follows is the way to smoke the best ribs you or anyone you know have ever tasted. Follow my instructions and give it a try. People at your party/cookout/campsite will tell you that they’re the best ribs they’ve ever had, and I will let you take all the credit. Yes, I fully realize this post is going to be longer than any post I’ve done yet. But let’s get serious here. Smoking meat is much more important, agreed? J In all honesty, this is a repeat of another blog I did, so I’m just copying and pasting. Step 1. Get some ribs. I actually really like Costco’s pack. They have both St. Louis and Baby Back. (They are the same ribs, but cut in half down the sides. St. Louis style is the ‘front’ of the ribs closest to the stomach, and ‘Baby back’ is the part of the ribs where is connects to the backbone). I like them both, so here you see I got one pack of each. About 4 racks to a pack. So these two packs for $25 each will feed about 16-20 of my guests. So around 3 bucks a person is a pretty good deal for the best ribs you’ll ever have. Step 2. Prep the ribs the night before you’re going to smoke. You need to trim them to fit your smoker racks, and also take off the membrane and add your rub. Then cover and set in fridge overnight. Here’s how to take off the membrane, which will not break down with heat and smoke like the rest of the meat, so must be removed. Use a butter knife to work in a ways between the membrane and the white bone. Just enough to make room for your finger. Try really hard not to poke through the membrane, you want to keep it whole. See how my gloved fingers can now start to lift up and pull off the membrane? This is what you are trying to do. It’s awesome when the whole thing can come off at once. This one is going great, maybe the best one I’ve ever done. Sometime, it falls apart and doesn't come off in one nice piece. I hate when that happens. Now, add your rub and pat it down once into the meat with your other hand. My rub is not secret. I got it from my mentor, a BBQ competitive chef who is currently ranked #1 in California and #3 in the nation on the BBQ circuit. He does full-day classes in southern California if anyone is interested in taking his class. Go to www.slapyodaddybbq.com to check him out. I tweaked his run recipe a tad and made my own. It’s one part Lawry’s, one part sugar, one part Montreal Steak Seasoning, one part garlic powder, one-half part red chili powder, one-half part paprika, and then 1/20th part cayenne. You can adjust that last ingredient, or leave it out. Real cheap stuff you can get at Costco. This lets you make enough rub to last about a year or two. Don’t make it all at once, make a shaker’s worth and use it up before you make more. Place it all in a bowl, mix well, and then add to a shaker like you see here. You can get a shaker with medium sized holes on it at any restaurant supply store or Smart & Final. The kind you see at pizza places for their red pepper flakes works best. Now cover and place in fridge overnight. Step 3. The next day. Ok, I’m ready to go. Get your stuff together. You will need your smoker, some good foil, a can of peach nectar, a bottle of Agave syrup, and a package of brown sugar. You will need this stuff later. I also use a clean spray bottle, and apple juice. Step 4. Make your fire, or turn on your electric smoker. In this example I’m using my portable charcoal smoker. I got this for only $40. I then modified it to be useful. Once modified, these guys actually work very well. Trust me, your food DOES NOT KNOW how expensive your smoker is. Someone who tells you that you need to spend a bunch of money on a smoker is an idiot. I also have an electric smoker that stays in my backyard. It’s cleaner and larger so I can smoke more food. But this little $40 one works great for going camping. Here is what my fire-bowl looks like. I leave a space in the middle open, and place cold charcoal and wood chucks in a circle going outwards. This makes it so when I dump the hot coals down the middle, they will slowly burn outwards, hitting different wood chucks at different times, allowing me to go 4-5 hours without having to even touch my fire. For ribs, I use apple and pecan wood. Pecan works for anything. Apple or any fruit wood is excellent for pork. So now I make my hot charcoal with a chimney only about half-full. I found a great use for that side-burner on my grill that I never use. It makes a fantastic chimney starter. You never use fluids of any kind, nor ever use that stupid charcoal that has lighter fluid built into it. Never, ever, ever. Step 5. Smoke. Add your ribs in the racks and stack them up in your smoker. I have a digital thermometer on a probe that I use to keep track of the temp in the smoker. I just lay the probe on the top rack and shut the lid. This cheap guy is a little harder to maintain the right temperature of around 225 F, so I do have to keep my eye on it more than my electric one or a more expensive charcoal one with the cool gadgets that regulate your temp for you. Every hour, spray apple juice all over your ribs using that spray bottle. After about 3 hours, you should have a very good crust (called the Bark) on your ribs. Once you have the Bark where you want it, carefully remove your ribs and place them in a tray. We are now ready for a very important part to make the flavor. Get a large piece of foil and place one rib section on it. Splash some of the peach nectar on it, and then a drizzle of the Agave syrup. Then, use your gloved hand to pack on some brown sugar. Do this on BOTH sides, and then completely wrap it up TIGHT in the foil. Do this for each rib section, and then place all the wrapped sections back into the smoker for another 4 to 6 hours. This is where the meat will get tender and flavorful. The first three hours is only to make the smoke bark. You don’t need smoke anymore, since the ribs are wrapped, you only need to keep the heat around 225 for the next 4-6 hours. Obviously you don’t spray anymore. Just time and slow heat. Be patient. It’s actually really hard to overdo it. You can let them go longer, and all that will happen is they will get even MORE tender!!! If you take them out too soon, they will be tough. How do you know? Take out one package (use long tongs) and open it up. If you grab a bone with your tongs and it just falls apart and breaks away from the rest of the meat, you are done!!! Enjoy!!! Step 6. Eat. It pulls apart like this when it’s done. By the way, smoking tri-tip is way easier. Just rub it with the same rub, and put in your smoker for about 2.5 hours at 250 F. That’s it. Low-maintenance. It comes out like this, with a fantastic smoke ring and amazing flavor. Thanks, and I will put up another good tip, about the ZFSSA, around the end of November. Steve 

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  • Game loop and time tracking

    - by David Brown
    Maybe I'm just an idiot, but I've been trying to implement a game loop all day and it's just not clicking. I've read literally every article I could find on Google, but the problem is that they all use different timing mechanisms, which makes them difficult to apply to my particular situation (some use milliseconds, other use ticks, etc). Basically, I have a Clock object that updates each time the game loop executes. internal class Clock { public static long Timestamp { get { return Stopwatch.GetTimestamp(); } } public static long Frequency { get { return Stopwatch.Frequency; } } private long _startTime; private long _lastTime; private TimeSpan _totalTime; private TimeSpan _elapsedTime; /// <summary> /// The amount of time that has passed since the first step. /// </summary> public TimeSpan TotalTime { get { return _totalTime; } } /// <summary> /// The amount of time that has passed since the last step. /// </summary> public TimeSpan ElapsedTime { get { return _elapsedTime; } } public Clock() { Reset(); } public void Reset() { _startTime = Timestamp; _lastTime = 0; _totalTime = TimeSpan.Zero; _elapsedTime = TimeSpan.Zero; } public void Tick() { long currentTime = Timestamp; if (_lastTime == 0) _lastTime = currentTime; _totalTime = TimestampToTimeSpan(currentTime - _startTime); _elapsedTime = TimestampToTimeSpan(currentTime - _lastTime); _lastTime = currentTime; } public static TimeSpan TimestampToTimeSpan(long timestamp) { return TimeSpan.FromTicks( (timestamp * TimeSpan.TicksPerSecond) / Frequency); } } I based most of that on the XNA GameClock, but it's greatly simplified. Then, I have a Time class which holds various times that the Update and Draw methods need to know. public class Time { public TimeSpan ElapsedVirtualTime { get; internal set; } public TimeSpan ElapsedRealTime { get; internal set; } public TimeSpan TotalVirtualTime { get; internal set; } public TimeSpan TotalRealTime { get; internal set; } internal Time() { } internal Time(TimeSpan elapsedVirtualTime, TimeSpan elapsedRealTime, TimeSpan totalVirutalTime, TimeSpan totalRealTime) { ElapsedVirtualTime = elapsedVirtualTime; ElapsedRealTime = elapsedRealTime; TotalVirtualTime = totalVirutalTime; TotalRealTime = totalRealTime; } } My main class keeps a single instance of Time, which it should constantly update during the game loop. So far, I have this: private static void Loop() { do { Clock.Tick(); Time.TotalRealTime = Clock.TotalTime; Time.ElapsedRealTime = Clock.ElapsedTime; InternalUpdate(Time); InternalDraw(Time); } while (!_exitRequested); } The real time properties of the time class turn out great. Now I'd like to get a proper update/draw loop working so that the state is updated a variable number of times per frame, but at a fixed timestep. At the same time, the Time.TotalVirtualTime and Time.ElapsedVirtualTime should be updated accordingly. In addition, I intend for this to support multiplayer in the future, in case that makes any difference to the design of the game loop. Any tips or examples on how I could go about implementing this (aside from links to articles)?

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  • Results Delphi users who wish to use HID USB in windows

    - by Lex Dean
    Results Delphi users who wish to use HID USB in windows HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\USB Contain a list if keys containing vender ID and Producer ID numbers that co inside with the USB web sites data base. These numbers and the GUID held within the key gives important information to execute the HID.dll that is otherwise imposable to execute. The Control Panel/System/Hardware/Device manager/USB Serial Bus Controllers/Mass Storage Devices/details simply lists the registry data. The access to the programmer has been documented through the API32.dll with a number of procedures that accesses the registry. But that is not the problem yet it looks like the problem!!!!!!!!! The key is info about the registry and how to use it. These keys are viewed in RegEdit.exe it’s self. Some parts of the registry like the USB have been given a windows security system type of protection with a Aurthz.dll to give the USB read and right protection. Even the api32.dll. Now only Microsoft give out these details and we all know Microsoft hate Delphi. Now C users have enjoyed this access for over 10 years now. Now some will make out that you should never give out such information because some idiot may make a stupid virus (true), but the argument is also do Delphi users need to be denied USB access for another ten years!!!!!!!!!!!!. What I do not have is the skill in is assembly code. I’m seeking for some one that can trace how regedit.exe gets its access through Aurthz.dll to access the USB data. So I’m asking all who reads this:- to partition any friend they have that has this skill to get the Aurthz.dll info needed. I find communicating with USB.org they reply when they have a positive email reply but do not bother should their email be a slightly negative policy. For all simple reasoning, all that USB had to do was to have a secure key as they have done, and to update the same data into a unsecured key every time the data is changed for USB developer to access. And not bother developers access to Aurthz.dll. Authz.dll with these functions for USB:- AuthzFreeResourceManager AuthzFreeContext AuthzAccessCheck(Flags: DWORD; AuthzClientContext: AUTHZ_CLIENT_CONTEXT_HANDLE; pRequest: PAUTHZ_ACCESS_REQUEST; AuditInfo: AUTHZ_AUDIT_INFO_HANDLE; pSecurityDescriptor: PSECURITY_DESCRIPTOR; OptionalSecurityDescriptorArray: PSECURITY_DESCRIPTOR; OptionalSecurityDescriptorCount: DWORD; //OPTIONAL, Var pReply: AUTHZ_ACCESS_REPLY; pAuthzHandle: PAUTHZ_ACCESS_CHECK_RESULTS_HANDLE): BOOl; AuthzInitializeContextFromSid(Flags: DWORD; UserSid: PSID; AuthzResourceManager: AUTHZ_RESOURCE_MANAGER_HANDLE; pExpirationTime: int64; Identifier: LUID; DynamicGroupArgs: PVOID; pAuthzClientContext: PAUTHZ_CLIENT_CONTEXT_HANDLE): BOOL; AuthzInitializeResourceManager(flags: DWORD; pfnAccessCheck: PFN_AUTHZ_DYNAMIC_ACCESS_CHECK; pfnComputeDynamicGroups: PFN_AUTHZ_COMPUTE_DYNAMIC_GROUPS; pfnFreeDynamicGroups: PFN_AUTHZ_FREE_DYNAMIC_GROUPS; ResourceManagerName: PWideChar; pAuthzResourceManager: PAUTHZ_RESOURCE_MANAGER_HANDLE): BOOL; further in Authz.h on kolers.com J Lex Dean.

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  • How to parse HTML with TouchXML or some other alternative.

    - by 0SX
    Hi, I'm trying to parse the HTML presented below with TouchXML but it keeps crashing when I try to extract certain attributes. I'm totally new to the parser world so I apologize for being a complete idiot. I need help to parse this HTML. What I'm trying to accomplish is to parse each attribute and value or what not and copy them to a string. I've been trying to find a good parser to parse HTML and I believe TouchXML is the best I've seen because of Tidy. Speaking of Tidy, How could I run this HTML through Tidy first then parse it? I'm not sure how to do this. Here is the code that I have so far that doesn't work due to it's not pulling everything I need from the HTML. Any help or advice would be much appreciated. Thanks My current code: NSMutableArray *res = [[NSMutableArray alloc] init]; // using local resource file NSString *XMLPath = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:@"example.html"]; NSData *XMLData = [NSData dataWithContentsOfFile:XMLPath]; CXMLDocument *doc = [[[CXMLDocument alloc] initWithData:XMLData options:0 error:nil] autorelease]; NSArray *nodes = NULL; nodes = [doc nodesForXPath:@"//div" error:nil]; for (CXMLElement *node in nodes) { NSMutableDictionary *item = [[NSMutableDictionary alloc] init]; [item setObject:[[node attributeForName:@"id"] stringValue] forKey:@"id"]; [res addObject:item]; [item release]; } NSLog(@"%@", res); [res release]; HTML file that needs to be parsed: <html> <head> <base target="_blank" /> </head> <body style="margin:2;"> <div id="group"> <div id="groupURL"><a href="http://www.example.com/groups">Group URL</a></div> <img id="grouplogo" src="http://images.example.com/groups/image.png" /> <div id="groupcomputer"><a href="http://www.example.com/groups/page" title="Group Title">Group title this would be here</a></div> <div id="groupinfos"> <div id="groupinfo-l">Person</div><div id="groupinfo-r">Ralph</div> <div id="groupinfo-l">Years</div><div id="groupinfo-r">4 years</div> <div id="groupinfo-l">Salary</div><div id="groupinfo-r">100K</div> <div id="groupinfo-l">Other</div><div id="groupoth" style="width:15px">other info</div> </body> </html> EDIT: I could use Element Parser but I need to know how to extract the Person's Name from the following example which would be Ralph in this case. <div id="groupinfo-l">Person</div><div id="groupinfo-r">Ralph</div>

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  • Why do I get "Sequence contains no elements"?

    - by Gary McGill
    NOTE: see edits at bottom. I am an idiot. I had the following code to process set of tag names and identify/process new ones: IEnumberable<string> tagNames = GetTagNames(); List<Tag> allTags = GetAllTags(); var newTagNames = tagNames.Where(n => !allTags.Any(t => t.Name == n)); foreach (var tagName in newTagNames) { // ... } ...and this worked fine, except that it failed to deal with cases where there's a tag called "Foo" and the list contains "foo". In other words, it wasn't doing a case-insensitive comparison. I changed the test to use a case-insensitive comparison, as follows: var newTagNames = tagNames.Where(n => !allTags.Any(t => t.Name.Equals(n, StringComparison.InvariantCultureIgnoreCase))); ... and suddenly I get an exception thrown when the foreach runs (and calls MoveNext on) newTagNames. The exception says: Sequence has no elements I'm confused by this. Why would foreach insist on the sequence being non-empty? I'd expect to see that error if I was calling First(), but not when using foreach? EDIT: more info. This is getting weirder by the minute. Because my code is in an async method, and I'm superstitious, I decided that there was too much "distance" between the point at which the exception is raised, and the point at which it's caught and reported. So, I put a try/catch around the offending code, in the hope of verifying that the exception being thrown really was what I thought it was. So now I can step through in the debugger to the foreach line, I can verify that the sequence is empty, and I can step right up to the bit where the debugger highlights the word "in". One more step, and I'm in my exception handler. But, not the exception handler I just added, no! It lands in my outermost exception handler, without visiting my recently-added one! It doesn't match catch (Exception ex) and nor does it match a plain catch. (I did also put in a finally, and verified that it does visit that on the way out). I've always taken it on faith that an Exception handler such as those would catch any exception. I'm scared now. I need an adult. EDIT 2: OK, so um, false alarm... The exception was not being caught by my local try/catch simply because it was not being raised by the code I thought. As I said above, I watched the execution in the debugger jump from the "in" of the foreach straight to the outer exception handler, hence my (wrong) assumption that that was where the error lay. However, with the empty enumeration, that was simply the last statement executed within the function, and for some reason the debugger did not show me the step out of the function or the execution of the next statement at the point of call - which was in fact the one causing the error. Apologies to all those who responded, and if you would like to create an answer saying that I am an idoit, I will gladly accept it. That is, if I ever show my face on SO again...

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  • css, unordered list not displaying icon in right place...

    - by Ronedog
    I'm really frustrated with this one. A few weeks ago I got it working in both firefox and ie just fine. Went back today to do some testing and found a problem with the display in firefox and I've been searching the code but can't find anything. I could use a few tips from anyone willing, I'm sure I'm looking at the wrong things. I upgraded my firefox version but I imagine my code is broke, not firefox. I'm assuming the problem is somewhere in my css file, but I'm not sure. Here's what I've confirmed so far. There don't seem to be conflicts in other css files with < ul 's or < li 's that may be overriding settings. The other confirmation is that This works fine in Internet Explorer...therefore I must be an idiot, because its usually been the other way around (working in FF, but failing in IE). Here's How it looks in IE (Notice the position of the folder icon right next to the text): Here's how it looks in FF (Notice the folder icon is not being pushed down with its corresponding text). Here's the Unordered List: <ul id="nav"> <li><a>Utah</a></li> <ul> <li><a>ParkCity</a> <ul> <li><a>Com1</a></li> <ul> <li class="folder_closed"><a>Timber</a></li> <div>SQUARE CONTAINER IS INSIDE THIS DIV</div> </ul> </ul> </ul> </ul> Here's the CSS that is used for the whole menu: /* MENU NAVIGATION (<UL><LI> LISTS ****************************************/ ul#nav{ /* This handles the main root <ul> */ margin-left:0; margin-right:0; padding-left:0px; text-indent:15px; } ul#nav div{ overflow: hidden; } #nav li>a:hover { cursor: pointer; } #nav li > ul{ /* This will hide any element with an id of "nav" and an "li" that has a direct child that is a "ul" */ display:none; margin-left:0px; margin-right:0px; padding-left:15px; padding-right:0px; text-indent:15px; } #nav li { list-style-type:none; list-style-image: none; } #nav > li{ vertical-align: top; left:0px; text-align:left; clear: both; margin:0px; margin-right:0px; padding-right:0px; } .menu_parent{ background-image: url(../images/maximize.png); background-repeat: no-repeat; background-position: 0px 1px; position:relative; } .menu_parent_minimized{ background-image: url(../images/minimize.png); background-repeat: no-repeat; background-position: 0px 1px; position:relative; } .folder_closed{ position:relative; background-image: url(../images/folder_closed12x14.png); background-repeat: no-repeat; background-position: 0px -2px; } .folder_open{ position:relative; background-image: url(../images/folder_open12x14.png); background-repeat: no-repeat; background-position: 0px -2px; } </ul>

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  • Ruby on Rails is complaining about a method that doesn't exist that is built into Active Record. Wha

    - by grg-n-sox
    This will probably just be a simple problem and I am just blind or an idiot but I could use some help. So I am going over some basic guides in Rails, reviewing the basics and such for an upcoming exam. One of the guides included was the sort-of-standard getting started guide over at guide.rubyonrails.org. Here is the link if you need it. Also all my code is for my app is from there, so I have no problem releasing any of my code since it should be the same as shown there. I didn't do a copy paste, but I basically was typing with Vim in one half of my screen and the web page in the other half, typing what I see. http://guides.rubyonrails.org/getting_started.html So like I said, I am going along the guide when I noticed past a certain point in the tutorial, I was always getting an error on the site. To find the section of code, just hit Ctrl+f on the page (or whatever you have search/find set to) and enter "accepts_". This should immediately direct you to this chunk of code. class Post < ActiveRecord::Base validates_presence_of :name, :title validates_length_of :title, :minimum => 5 has_many :comments has_many :tags accepts_nested_attributes_for :tags, :allow_destroy => :true , :reject_if => proc { |attrs| attrs.all? { |k, v| v.blank? } } end So I tried putting this in my code. It is in ~/Rails/blog/app/models/post.rb in case you are wondering. However, even after all the other code I put in past that in the guide, hoping I was just missing some line of code that would come up later in the guide. But nothing, same error every time. This is what I get. NoMethodError in PostsController#index undefined method `accepts_nested_attributes_for' for #<Class:0xb7109f98> /usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/base.rb:1833:in `method_missing' app/models/post.rb:7 app/controllers/posts_controller.rb:9:in `index' Request Parameters: None Response Headers: {"Content-Type"=>"", "cookie"=>[], "Cache-Control"=>"no-cache"} Now, I copied the above code from the guide. The two code sections I edited mentioned in the error message I will paste as is below. class PostsController < ApplicationController # GET /posts # GET /posts.xml before_filter :find_post, :only => [:show, :edit, :update, :destroy] def index @posts = Post.find(:all) # <= the line 9 referred to in error message respond_to do |format| format.html # index.html.erb format.xml { render :xml => @posts } end end class Post < ActiveRecord::Base validates_presence_of :name, :title validates_length_of :title, :minimum => 5 has_many :comments has_many :tags accepts_nested_attributes_for :tags, :allow_destroy => :true , # <= problem :reject_if => proc { |attrs| attrs.all? { |k, v| v.blank? } } end Also here is gem local gem list. I do note that they are a bit out of date, but the default Rails install any of the school machines (an environment likely for my exam) is basically 'gem install rails --version 2.2.2' and since they are windows machines, they come with all the normal windows ruby gems that comes with the ruby installer. However, I am running this off a Debian virtual machine of mine, but trying to set it up similarly and I figured the windows ruby gems wouldn't change anything in Rails. *** LOCAL GEMS *** actionmailer (2.2.2) actionpack (2.2.2) activerecord (2.2.2) activeresource (2.2.2) activesupport (2.2.2) gem_plugin (0.2.3) hpricot (0.8.2) linecache (0.43) log4r (1.1.7) ptools (1.1.9) rack (1.1.0) rails (2.2.2) rake (0.8.7) sqlite3-ruby (1.2.3) So any ideas on what the problem is? Thanks in advanced.

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  • File Segmentation when trying to write in a file

    - by user1286390
    I am trying in C language to use the method of bisection to find the roots of some equation, however when I try to write every step of this process in a file I get the problem "Segmentation fault". This might be an idiot fault that I did, however I have been trying to solve this for a long time. I am compiling using gcc and that is the code: #include <stdio.h> #include <stdlib.h> #include <math.h> #define R 1.0 #define h 1.0 double function(double a); void attractor(double *a1, double *a2, double *epsilon); void attractor(double *a1, double *a2, double *epsilon) { FILE* bisection; double a2_copia, a3, fa1, fa2; bisection = fopen("bisection-part1.txt", "w"); fa1 = function(*a1); fa2 = function(*a2); if(function(*a1) - function(*a2) > 0.0) *epsilon = function(*a1) - function(*a2); else *epsilon = function(*a2) - function(*a1); fprintf(bisection, "a1 a2 fa1 fa2 epsilon\n"); a2_copia = 0.0; if(function(*a1) * function(*a2) < 0.0 && *epsilon >= 0.00001) { a3 = *a2 - (*a2 - *a1); a2_copia = *a2; *a2 = a3; if(function(*a1) - function(*a2) > 0.0) *epsilon = function(*a1) - function(*a2); else *epsilon = function(*a2) - function(*a1); if(function(*a1) * function(*a2) < 0.0 && *epsilon >= 0.00001) { fprintf(bisection, "%.4f %.4f %.4f %.4f %.4f\n", *a1, *a2, function(*a1), function(*a1), *epsilon); attractor(a1, a2, epsilon); } else { *a2 = a2_copia; *a1 = a3; if(function(*a1) - function(*a2) > 0) *epsilon = function(*a1) - function(*a2); else *epsilon = function(*a2) - function(*a1); if(function(*a1) * function(*a2) < 0.0 && *epsilon >= 0.00001) { fprintf(bisection, "%.4f %.4f %.4f %.4f %.4f\n", *a1, *a2, function(*a1), function(*a1), *epsilon); attractor(a1, a2, epsilon); } } } fa1 = function(*a1); fa2 = function(*a2); if(function(*a1) - function(*a2) > 0.0) *epsilon = function(*a1) - function(*a2); else *epsilon = function(*a2) - function(*a1); fprintf(bisection, "%.4f %.4f %.4f %.4f %.4f\n", a1, a2, fa1, fa2, epsilon); } double function(double a) { double fa; fa = (a * cosh(h / (2 * a))) - R; return fa; } int main() { double a1, a2, fa1, fa2, epsilon; a1 = 0.1; a2 = 0.5; fa1 = function(a1); fa2 = function(a2); if(fa1 - fa2 > 0.0) epsilon = fa1 - fa2; else epsilon = fa2 - fa1; if(epsilon >= 0.00001) { fa1 = function(a1); fa2 = function(a2); attractor(&a1, &a2, &epsilon); fa1 = function(a1); fa2 = function(a2); if(fa1 - fa2 > 0.0) epsilon = fa1 - fa2; else epsilon = fa2 - fa1; } if(epsilon < 0.0001) printf("Vanish at %f", a2); else printf("ERROR"); return 0; } Thanks anyway and sorry if this question is not suitable.

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  • The Windows Store... why did I sign up with this mess again?

    - by FransBouma
    Yesterday, Microsoft revealed that the Windows Store is now open to all developers in a wide range of countries and locations. For the people who think "wtf is the 'Windows Store'?", it's the central place where Windows 8 users will be able to find, download and purchase applications (or as we now have to say to not look like a computer illiterate: <accent style="Kentucky">aaaaappss</accent>) for Windows 8. As this is the store which is integrated into Windows 8, it's an interesting place for ISVs, as potential customers might very well look there first. This of course isn't true for all kinds of software, and developer tools in general aren't the kind of applications most users will download from the Windows store, but a presence there can't hurt. Now, this Windows Store hosts two kinds of applications: 'Metro-style' applications and 'Desktop' applications. The 'Metro-style' applications are applications created for the new 'Metro' UI which is present on Windows 8 desktop and Windows RT (the single color/big font fingerpaint-oriented UI). 'Desktop' applications are the applications we all run and use on Windows today. Our software are desktop applications. The Windows Store hosts all Metro-style applications locally in the store and handles the payment for these applications. This means you upload your application (sorry, 'app') to the store, jump through a lot of hoops, Microsoft verifies that your application is not violating a tremendous long list of rules and after everything is OK, it's published and hopefully you get customers and thus earn money. Money which Microsoft will pay you on a regular basis after customers buy your application. Desktop applications are not following this path however. Desktop applications aren't hosted by the Windows Store. Instead, the Windows Store more or less hosts a page with the application's information and where to get the goods. I.o.w.: it's nothing more than a product's Facebook page. Microsoft will simply redirect a visitor of the Windows Store to your website and the visitor will then use your site's system to purchase and download the application. This last bit of information is very important. So, this morning I started with fresh energy to register our company 'Solutions Design bv' at the Windows Store and our two applications, LLBLGen Pro and ORM Profiler. First I went to the Windows Store dashboard page. If you don't have an account, you have to log in or sign up if you don't have a live account. I signed in with my live account. After that, it greeted me with a page where I had to fill in a code which was mailed to me. My local mail server polls every several minutes for email so I had to kick it to get it immediately. I grabbed the code from the email and I was presented with a multi-step process to register myself as a company or as an individual. In red I was warned that this choice was permanent and not changeable. I chuckled: Microsoft apparently stores its data on paper, not in digital form. I chose 'company' and was presented with a lengthy form to fill out. On the form there were two strange remarks: Per company there can just be 1 (one, uno, not zero, not two or more) registered developer, and only that developer is able to upload stuff to the store. I have no idea how this works with large companies, oh the overhead nightmares... "Sorry, but John, our registered developer with the Windows Store is on holiday for 3 months, backpacking through Australia, no, he's not reachable at this point. M'yeah, sorry bud. Hey, did you fill in those TPS reports yesterday?" A separate Approver has to be specified, which has to be a different person than the registered developer. Apparently to Microsoft a company with just 1 person is not a company. Luckily we're with two people! *pfew*, dodged that one, otherwise I would be stuck forever: the choice I already made was not reversible! After I had filled out the form and it was all well and good and accepted by the Microsoft lackey who had to write it all down in some paper notebook ("Hey, be warned! It's a permanent choice! Written down in ink, can't be changed!"), I was presented with the question how I wanted to pay for all this. "Pay for what?" I wondered. Must be the paper they were scribbling the information on, I concluded. After all, there's a financial crisis going on! How could I forget! Silly me. "Ok fair enough". The price was 75 Euros, not the end of the world. I could only pay by credit card, so it was accepted quickly. Or so I thought. You see, Microsoft has a different idea about CC payments. In the normal world, you type in your CC number, some date, a name and a security code and that's it. But Microsoft wants to verify this even more. They want to make a verification purchase of a very small amount and are doing that with a special code in the description. You then have to type in that code in a special form in the Windows Store dashboard and after that you're verified. Of course they'll refund the small amount they pull from your card. Sounds simple, right? Well... no. The problem starts with the fact that I can't see the CC activity on some website: I have a bank issued CC card. I get the CC activity once a month on a piece of paper sent to me. The bank's online website doesn't show them. So it's possible I have to wait for this code till October 12th. One month. "So what, I'm not going to use it anyway, Desktop applications don't use the payment system", I thought. "Haha, you're so naive, dear developer!" Microsoft won't allow you to publish any applications till this verification is done. So no application publishing for a month. Wouldn't it be nice if things were, you know, digital, so things got done instantly? But of course, that lackey who scribbled everything in the Big Windows Store Registration Book isn't that quick. Can't blame him though. He's just doing his job. Now, after the payment was done, I was presented with a page which tells me Microsoft is going to use a third party company called 'Symantec', which will verify my identity again. The page explains to me that this could be done through email or phone and that they'll contact the Approver to verify my identity. "Phone?", I thought... that's a little drastic for a developer account to publish a single page of information about an external hosted software product, isn't it? On Facebook I just added a page, done. And paying you, Microsoft, took less information: you were happy to take my money before my identity was even 'verified' by this 3rd party's minions! "Double standards!", I roared. No-one cared. But it's the thought of getting it off your chest, you know. Luckily for me, everyone at Symantec was asleep when I was registering so they went for the fallback option in case phone calls were not possible: my Approver received an email. Imagine you have to explain the idiot web of security theater I was caught in to someone else who then has to reply a random person over the internet that I indeed was who I said I was. As she's a true sweetheart, she gave me the benefit of the doubt and assured that for now, I was who I said I was. Remember, this is for a desktop application, which is only a link to a website, some pictures and a piece of text. No file hosting, no payment processing, nothing, just a single page. Yeah, I also thought I was crazy. But we're not at the end of this quest yet. I clicked around in the confusing menus of the Windows Store dashboard and found the 'Desktop' section. I get a helpful screen with a warning in red that it can't find any certified 'apps'. True, I'm just getting started, buddy. I see a link: "Check the Windows apps you submitted for certification". Well, I haven't submitted anything, but let's see where it brings me. Oh the thrill of adventure! I click the link and I end up on this site: the hardware/desktop dashboard account registration. "Erm... but I just registered...", I mumbled to no-one in particular. Apparently for desktop registration / verification I have to register again, it tells me. But not only that, the desktop application has to be signed with a certificate. And not just some random el-cheapo certificate you can get at any mall's discount store. No, this certificate is special. It's precious. This certificate, the 'Microsoft Authenticode' Digital Certificate, is the only certificate that's acceptable, and jolly, it can be purchased from VeriSign for the price of only ... $99.-, but be quick, because this is a limited time offer! After that it's, I kid you not, $499.-. 500 dollars for a certificate to sign an executable. But, I do feel special, I got a special price. Only for me! I'm glowing. Not for long though. Here I started to wonder, what the benefit of it all was. I now again had to pay money for a shiny certificate which will add 'Solutions Design bv' to our installer as the publisher instead of 'unknown', while our customers download the file from our website. Not only that, but this was all about a Desktop application, which wasn't hosted by Microsoft. They only link to it. And make no mistake. These prices aren't single payments. Every year these have to be renewed. Like a membership of an exclusive club: you're special and privileged, but only if you cough up the dough. To give you an example how silly this all is: I added LLBLGen Pro and ORM Profiler to the Visual Studio Gallery some time ago. It's the same thing: it's a central place where one can find software which adds to / extends / works with Visual Studio. I could simply create the pages, add the information and they show up inside Visual Studio. No files are hosted at Microsoft, they're downloaded from our website. Exactly the same system. As I have to wait for the CC transcripts to arrive anyway, I can't proceed with publishing in this new shiny store. After the verification is complete I have to wait for verification of my software by Microsoft. Even Desktop applications need to be verified using a long list of rules which are mainly focused on Metro-style applications. Even while they're not hosted by Microsoft. I wonder what they'll find. "Your application wasn't approved. It violates rule 14 X sub D: it provides more value than our own competing framework". While I was writing this post, I tried to check something in the Windows Store Dashboard, to see whether I remembered it correctly. I was presented again with the question, after logging in with my live account, to enter the code that was just mailed to me. Not the previous code, a brand new one. Again I had to kick my mail server to pull the email to proceed. This was it. This 'experience' is so beyond miserable, I'm afraid I have to say goodbye for now to the 'Windows Store'. It's simply not worth my time. Now, about live accounts. You might know this: live accounts are tied to everything you do with Microsoft. So if you have an MSDN subscription, e.g. the one which costs over $5000.-, it's tied to this same live account. But the fun thing is, you can login with your live account to the MSDN subscriptions with just the account id and password. No additional code is mailed to you. While it gives you access to all Microsoft software available, including your licenses. Why the draconian security theater with this Windows Store, while all I want is to publish some desktop applications while on other Microsoft sites it's OK to simply sign in with your live account: no codes needed, no verification and no certificates? Microsoft, one thing you need with this store and that's: apps. Apps, apps, apps, apps, aaaaaaaaapps. Sorry, my bad, got carried away. I just can't stand the word 'app'. This store's shelves have to be filled to the brim with goods. But instead of being welcomed into the store with open arms, I have to fight an uphill battle with an endless list of rules and bullshit to earn the privilege to publish in this shiny store. As if I have to be thrilled to be one of the exclusive club called 'Windows Store Publishers'. As if Microsoft doesn't want it to succeed. Craig Stuntz sent me a link to an old blog post of his regarding code signing and uploading to Microsoft's old mobile store from back in the WinMo5 days: http://blogs.teamb.com/craigstuntz/2006/10/11/28357/. Good read and good background info about how little things changed over the years. I hope this helps Microsoft make things more clearer and smoother and also helps ISVs with their decision whether to go with the Windows Store scheme or ignore it. For now, I don't see the advantage of publishing there, especially not with the nonsense rules Microsoft cooked up. Perhaps it changes in the future, who knows.

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  • linux thread synchronization

    - by johnnycrash
    I am new to linux and linux threads. I have spent some time googling to try to understand the differences between all the functions available for thread synchronization. I still have some questions. I have found all of these different types of synchronizations, each with a number of functions for locking, unlocking, testing the lock, etc. gcc atomic operations futexes mutexes spinlocks seqlocks rculocks conditions semaphores My current (but probably flawed) understanding is this: semaphores are process wide, involve the filesystem (virtually I assume), and are probably the slowest. Futexes might be the base locking mechanism used by mutexes, spinlocks, seqlocks, and rculocks. Futexes might be faster than the locking mechanisms that are based on them. Spinlocks dont block and thus avoid context swtiches. However they avoid the context switch at the expense of consuming all the cycles on a CPU until the lock is released (spinning). They should only should be used on multi processor systems for obvious reasons. Never sleep in a spinlock. The seq lock just tells you when you finished your work if a writer changed the data the work was based on. You have to go back and repeat the work in this case. Atomic operations are the fastest synch call, and probably are used in all the above locking mechanisms. You do not want to use atomic operations on all the fields in your shared data. You want to use a lock (mutex, futex, spin, seq, rcu) or a single atomic opertation on a lock flag when you are accessing multiple data fields. My questions go like this: Am I right so far with my assumptions? Does anyone know the cpu cycle cost of the various options? I am adding parallelism to the app so we can get better wall time response at the expense of running fewer app instances per box. Performances is the utmost consideration. I don't want to consume cpu with context switching, spinning, or lots of extra cpu cycles to read and write shared memory. I am absolutely concerned with number of cpu cycles consumed. Which (if any) of the locks prevent interruption of a thread by the scheduler or interrupt...or am I just an idiot and all synchonization mechanisms do this. What kinds of interruption are prevented? Can I block all threads or threads just on the locking thread's CPU? This question stems from my fear of interrupting a thread holding a lock for a very commonly used function. I expect that the scheduler might schedule any number of other workers who will likely run into this function and then block because it was locked. A lot of context switching would be wasted until the thread with the lock gets rescheduled and finishes. I can re-write this function to minimize lock time, but still it is so commonly called I would like to use a lock that prevents interruption...across all processors. I am writing user code...so I get software interrupts, not hardware ones...right? I should stay away from any functions (spin/seq locks) that have the word "irq" in them. Which locks are for writing kernel or driver code and which are meant for user mode? Does anyone think using an atomic operation to have multiple threads move through a linked list is nuts? I am thinking to atomicly change the current item pointer to the next item in the list. If the attempt works, then the thread can safely use the data the current item pointed to before it was moved. Other threads would now be moved along the list. futexes? Any reason to use them instead of mutexes? Is there a better way than using a condition to sleep a thread when there is no work? When using gcc atomic ops, specifically the test_and_set, can I get a performance increase by doing a non atomic test first and then using test_and_set to confirm? *I know this will be case specific, so here is the case. There is a large collection of work items, say thousands. Each work item has a flag that is initialized to 0. When a thread has exclusive access to the work item, the flag will be one. There will be lots of worker threads. Any time a thread is looking for work, they can non atomicly test for 1. If they read a 1, we know for certain that the work is unavailable. If they read a zero, they need to perform the atomic test_and_set to confirm. So if the atomic test_and_set is 500 cpu cycles because it is disabling pipelining, causes cpu's to communicate and L2 caches to flush/fill .... and a simple test is 1 cycle .... then as long as I had a better ratio of 500 to 1 when it came to stumbling upon already completed work items....this would be a win.* I hope to use mutexes or spinlocks to sparilngly protect sections of code that I want only one thread on the SYSTEM (not jsut the CPU) to access at a time. I hope to sparingly use gcc atomic ops to select work and minimize use of mutexes and spinlocks. For instance: a flag in a work item can be checked to see if a thread has worked it (0=no, 1=yes or in progress). A simple test_and_set tells the thread if it has work or needs to move on. I hope to use conditions to wake up threads when there is work. Thanks!

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  • Help needed with Javascript Variable Scope / OOP and Call Back Functions

    - by gargantaun
    I think this issue goes beyond typical variable scope and closure stuff, or maybe I'm an idiot. Here goes anyway... I'm creating a bunch of objects on the fly in a jQuery plugin. The object look something like this function WedgePath(canvas){ this.targetCanvas = canvas; this.label; this.logLabel = function(){ console.log(this.label) } } the jQuery plugin looks something like this (function($) { $.fn.myPlugin = function() { return $(this).each(function() { // Create Wedge Objects for(var i = 1; i <= 30; i++){ var newWedge = new WedgePath(canvas); newWedge.label = "my_wedge_"+i; globalFunction(i, newWedge]); } }); } })(jQuery); So... the plugin creates a bunch of wedgeObjects, then calls 'globalFunction' for each one, passing in the latest WedgePath instance. Global function looks like this. function globalFunction(indicator_id, pWedge){ var targetWedge = pWedge; targetWedge.logLabel(); } What happens next is that the console logs each wedges label correctly. However, I need a bit more complexity inside globalFunction. So it actually looks like this... function globalFunction(indicator_id, pWedge){ var targetWedge = pWedge; someSql = "SELECT * FROM myTable WHERE id = ?"; dbInterface.executeSql(someSql, [indicator_id], function(transaction, result){ targetWedge.logLabel(); }) } There's a lot going on here so i'll explain. I'm using client side database storage (WebSQL i call it). 'dbInterface' an instance of a simple javascript object I created which handles the basics of interacting with a client side database [shown at the end of this question]. the executeSql method takes up to 4 arguments The SQL String an optional arguments array an optional onSuccess handler an optional onError handler (not used in this example) What I need to happen is: When the WebSQL query has completed, it takes some of that data and manipulates some attribute of a particular wedge. But, when I call 'logLabel' on an instance of WedgePath inside the onSuccess handler, I get the label of the very last instance of WedgePath that was created way back in the plugin code. Now I suspect that the problem lies in the var newWedge = new WedgePath(canvas); line. So I tried pushing each newWedge into an array, which I thought would prevent that line from replacing or overwriting the WedgePath instance at every iteration... wedgeArray = []; // Inside the plugin... for(var i = 1; i <= 30; i++){ var newWedge = new WedgePath(canvas); newWedge.label = "my_wedge_"+i; wedgeArray.push(newWedge); } for(var i = 0; i < wedgeArray.length; i++){ wedgeArray[i].logLabel() } But again, I get the last instance of WedgePath to be created. This is driving me nuts. I apologise for the length of the question but I wanted to be as clear as possible. END ============================================================== Also, here's the code for dbInterface object should it be relevant. function DatabaseInterface(db){ var DB = db; this.sql = function(sql, arr, pSuccessHandler, pErrorHandler){ successHandler = (pSuccessHandler) ? pSuccessHandler : this.defaultSuccessHandler; errorHandler = (pErrorHandler) ? pErrorHandler : this.defaultErrorHandler; DB.transaction(function(tx){ if(!arr || arr.length == 0){ tx.executeSql(sql, [], successHandler, errorHandler); }else{ tx.executeSql(sql,arr, successHandler, errorHandler) } }); } // ---------------------------------------------------------------- // A Default Error Handler // ---------------------------------------------------------------- this.defaultErrorHandler = function(transaction, error){ // error.message is a human-readable string. // error.code is a numeric error code console.log('WebSQL Error: '+error.message+' (Code '+error.code+')'); // Handle errors here var we_think_this_error_is_fatal = true; if (we_think_this_error_is_fatal) return true; return false; } // ---------------------------------------------------------------- // A Default Success Handler // This doesn't do anything except log a success message // ---------------------------------------------------------------- this.defaultSuccessHandler = function(transaction, results) { console.log("WebSQL Success. Default success handler. No action taken."); } }

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