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  • Session Report - Java on the Raspberry Pi

    - by Janice J. Heiss
    On mid-day Wednesday, the always colorful Oracle Evangelist Simon Ritter demonstrated Java on the Raspberry Pi at his session, “Do You Like Coffee with Your Dessert?”. The Raspberry Pi consists of a credit card-sized single-board computer developed in the UK with the intention of stimulating the teaching of basic computer science in schools. “I don't think there is a single feature that makes the Raspberry Pi significant,” observed Ritter, “but a combination of things really makes it stand out. First, it's $35 for what is effectively a completely usable computer. You do have to add a power supply, SD card for storage and maybe a screen, keyboard and mouse, but this is still way cheaper than a typical PC. The choice of an ARM (Advanced RISC Machine and Acorn RISC Machine) processor is noteworthy, because it avoids problems like cooling (no heat sink or fan) and can use a USB power brick. When you add in the enormous community support, it offers a great platform for teaching everyone about computing.”Some 200 enthusiastic attendees were present at the session which had the feel of Simon Ritter sharing a fun toy with friends. The main point of the session was to show what Oracle was doing to support Java on the Raspberry Pi in a way that is entertaining and fun. Ritter pointed out that, in addition to being great for teaching, it’s an excellent introduction to the ARM architecture, and runs well with Java and will get better once it has official hard float support. The possibilities are vast.Ritter explained that the Raspberry Pi Project started in 2006 with the goal of devising a computer to inspire children; it drew inspiration from the BBC Micro literacy project of 1981 that produced a series of microcomputers created by the Acorn Computer company. It was officially launched on February 29, 2012, with a first production of 10,000 boards. There were 100,000 pre-orders in one day; currently about 4,000 boards are produced a day. Ritter described the specification as follows:* CPU: ARM 11 core running at 700MHz Broadcom SoC package Can now be overclocked to 1GHz (without breaking the warranty!) * Memory: 256Mb* I/O: HDMI and composite video 2 x USB ports (Model B only) Ethernet (Model B only) Header pins for GPIO, UART, SPI and I2C He took attendees through a brief history of ARM Architecture:* Acorn BBC Micro (6502 based) Not powerful enough for Acorn’s plans for a business computer * Berkeley RISC Project UNIX kernel only used 30% of instruction set of Motorola 68000 More registers, less instructions (Register windows) One chip architecture to come from this was… SPARC * Acorn RISC Machine (ARM) 32-bit data, 26-bit address space, 27 registers First machine was Acorn Archimedes * Spin off from Acorn, Advanced RISC MachinesNext he presented its features:* 32-bit RISC Architecture–  ARM accounts for 75% of embedded 32-bit CPUs today– 6.1 Billion chips sold last year (zero manufactured by ARM)* Abstract architecture and microprocessor core designs– Raspberry Pi is ARM11 using ARMv6 instruction set* Low power consumption– Good for mobile devices– Raspberry Pi can be powered from 700mA 5V only PSU– Raspberry Pi does not require heatsink or fanHe described the current ARM Technology:* ARMv6– ARM 11, ARM Cortex-M* ARMv7– ARM Cortex-A, ARM Cortex-M, ARM Cortex-R* ARMv8 (Announced)– Will support 64-bit data and addressingHe next gave the Java Specifics for ARM: Floating point operations* Despite being an ARMv6 processor it does include an FPU– FPU only became standard as of ARMv7* FPU (Hard Float, or HF) is much faster than a software library* Linux distros and Oracle JVM for ARM assume no HF on ARMv6– Need special build of both– Raspbian distro build now available– Oracle JVM is in the works, release date TBDNot So RISCPerformance Improvements* DSP Enhancements* Jazelle* Thumb / Thumb2 / ThumbEE* Floating Point (VFP)* NEON* Security Enhancements (TrustZone)He spent a few minutes going over the challenges of using Java on the Raspberry Pi and covered:* Sound* Vision * Serial (TTL UART)* USB* GPIOTo implement sound with Java he pointed out:* Sound drivers are now included in new distros* Java Sound API– Remember to add audio to user’s groups– Some bits work, others not so much* Playing (the right format) WAV file works* Using MIDI hangs trying to open a synthesizer* FreeTTS text-to-speech– Should work once sound works properlyHe turned to JavaFX on the Raspberry Pi:* Currently internal builds only– Will be released as technology preview soon* Work involves optimal implementation of Prism graphics engine– X11?* Once the JavaFX implementation is completed there will be little of concern to developers-- It’s just Java (WORA). He explained the basis of the Serial Port:* UART provides TTL level signals (3.3V)* RS-232 uses 12V signals* Use MAX3232 chip to convert* Use this for access to serial consoleHe summarized his key points. The Raspberry Pi is a very cool (and cheap) computer that is great for teaching, a great introduction to ARM that works very well with Java and will work better in the future. The opportunities are limitless. For further info, check out, Raspberry Pi User Guide by Eben Upton and Gareth Halfacree. From there, Ritter tried out several fun demos, some of which worked better than others, but all of which were greeted with considerable enthusiasm and support and good humor (even when he ran into some glitches).  All in all, this was a fun and lively session.

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  • SQL: Speed Improvement - Cluttered union query

    - by vol7ron
    SELECT * FROM ( SELECT a.user_id, a.f_name, a.l_name, b.user_id, b.f_name, b.l_name FROM current_tbl a INNER JOIN import_tbl b ON ( a.user_id = b.user_id ) UNION SELECT a.user_id, a.f_name, a.l_name, b.user_id, b.f_name, b.l_name FROM current_tbl a INNER JOIN import_tbl b ON ( lower(a.f_name)=lower(b.f_name) AND lower(a.l_name)=lower(b.l_name) ) ) foo -- UNION -- SELECT a.user_id , a.f_name , a.l_name , '' , '' , '' FROM current_tbl a WHERE a.user_id NOT IN ( select user_id from( SELECT a.user_id, a.f_name, a.l_name, b.user_id, b.f_name, b.l_name FROM current_tbl a INNER JOIN import_tbl b ON ( a.user_id = b.user_id ) UNION SELECT a.user_id, a.f_name, a.l_name, b.user_id, b.f_name, b.l_name FROM current_tbl a INNER JOIN import_tbl b ON ( lower(a.f_name)=lower(b.f_name) AND lower(a.l_name)=lower(b.l_name) ) ) bar ) ORDER BY user_id Example of table population: current_tbl: ------------------------------- user_id | f_name | l_name ---------+----------+---------- A1 | Adam | Acorn A2 | Beth | Berry A3 | Calv | Chard | | import_tbl: ------------------------------- user_id | f_name | l_name ---------+----------+---------- A1 | Adam | Acorn A2 | Beth | Butcher <- last_name different | | Expected Output: ----------------------------------------------------------------------- user_id1 | f_name1 | l_name1 | user_id2 | f_name2 | l_name2 ----------+-----------+-----------+------------+-----------+----------- A1 | Adam | Acorn | A1 | Adam | Acorn A2 | Beth | Berry | A2 | Beth | Butcher A3 | Calv | Chard | | | Doing this method gets rid of conditions where the row would be: A2 | Beth | Berry | A2 | Beth | Butcher But it keeps the A3 row I hope this makes sense and I haven't overly simplified it. This is a continuation question from my other question. The succession of these improvements has dropped the query down from ~32000ms to where it's at now ~1200ms - quite an improvement. I supect I can optimize by using UNION ALL in the subquery and of course the usual index optimizations, but I'm looking for the best SQL optimization. FYI this particular case is for PostgreSQL.

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  • Make an element visible to the user but invisible to events

    - by Acorn
    I'm not quite sure how to describe what I'm looking to do, but I'll do my best. At the moment I have a parent <div>, with absolutely positioned child <div>s within it, and I'm tracking the mouse pointer location coordinates relative to the element your mouse is over. At the moment, when I mouse over my child <div>s, I get the mouse location relative to them, but I want the coordinates to be relative the the parent <div> even when mousing over the child elements. So I basically want the child elements to be visible, but transparent to the mousemove, so I want the mousemove to go straight through to the parent element. How would I do this? Do I maybe need to somehow make the parent <div> be in the forground but still have the child <div>s show through? or make a transparent <div> overlay just to get the mouse coordinates? Here's a link to the page I'm experimenting on: http://acorn.host22.com/mouse.html

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  • Monitoring whether Google Apps email address is reachable

    - by Acorn
    Backstory: I bungled things a bit the other day, and inadvertantly deleted the DNS overrides for my domain including the MX records that point to Google Apps, causing 2 days of lost emails. What I want: I want to be able to monitor the email address/account so that I can be alerted if for any reason something has gone wrong and emails aren't arriving. Thoughts: I was thinking there might be a way to test the email without having to send an actual message. Does this exist? This wouldn't help if the DNS has reset itself to a different mailserver would it? The other idea was sending periodic emails to check the address it working. How would you automate this? You'd need to somehow check that the email address had arrived as well as checking if it had bounced. Are there any scripts that exist that would do something like this? What would be the best method? Maybe a combination of checking that the MX records for the domain are set to what they're supposed to be set to, and sending automatic test emails to check that things are still functioning on the Google Apps end?

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  • Making an element unselectable using jQuery

    - by Acorn
    What's the best way to make an element unselectable using jQuery? I know you can use onselectstart="return false;" ondragstart="return false;" in the HTML, but I'm not sure how cross browser compatible that is. I also see someone's made a jQuery plugin: http://plugins.jquery.com/project/Unselectable .. would a plugin like that be necessary? Is there a simple, compatible way to make an element unselectable? The reason for wanting to do this is purely aesthetic. With webpages that have dragging or click events, it's not very nice when things get selected.

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  • Finding the closest grid coordinate to the mouse position with javascript/jQuery

    - by Acorn
    What I'm trying to do is make a grid of invisible coordinates on the page equally spaced. I then want a <div> to be placed at whatever grid coordinate is closest to the pointer when onclick is triggered. Here's the rough idea: I have the tracking of the mouse coordinates and the placing of the <div> worked out fine. What I'm stuck with is how to approach the problem of the grid of coordinates. First of all, should I have all my coordinates in an array which I then compare my onclick coordinate to? Or seeing as my grid coordinates follow a rule, could I do something like finding out which coordinate that is a multiple of whatever my spacing is is closest to the onclick coordinate? And then, where do I start with working out which grid point coordinate is closest? What's the best way of going about it? Thanks!

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  • How to give an error when no options are given with optparse

    - by Acorn
    I'm try to work out how to use optparse, but I've come to a problem. My script (represented by this simplified example) takes a file, and does different things to it depending on options that are parsed to it. If no options are parsed nothing is done. It makes sense to me that because of this, an error should be given if no options are given by the user. I can't work out how to do this. Am I using options in the wrong way? If so, how should I be doing it instead? #!/usr/bin/python from optparse import OptionParser dict = {'name': foo, 'age': bar} parser = OptionParser() parser.add_option("-n", "--name", dest="name") parser.add_option("-a", "--age", dest="age") (options, args) = parser.parse_args() if options.name: dict['name'] = options.name if options.age: dict['age'] = options.age print dict #END

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  • Finding the closest grid coordinate to the mouse onclick with javascript/jQuery

    - by Acorn
    What I'm trying to do is make a grid of invisible coordinates on the page equally spaced. I then want a <div> to be placed at whatever grid coordinate is closest to the pointer when onclick is triggered. Here's the rough idea: I have the tracking of the mouse coordinates and the placing of the <div> worked out fine. What I'm stuck with is how to approach the problem of the grid of coordinates. First of all, should I have all my coordinates in an array which I then compare my onclick coordinate to? Or seeing as my grid coordinates follow a rule, could I do something like finding out which coordinate that is a multiple of whatever my spacing is is closest to the onclick coordinate? And then, where do I start with working out which grid point coordinate is closest? What's the best way of going about it? Thanks!

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  • How to get the original variable name of variable passed to a function

    - by Acorn
    Is it possible to get the original variable name of a variable passed to a function? E.g. foobar = "foo" def func(var): print var.origname So that: func(foobar) Returns: >>foobar EDIT: All I was trying to do was make a function like: def log(soup): f = open(varname+'.html', 'w') print >>f, soup.prettify() f.close() .. and have the function generate the filename from the name of the variable passed to it. I suppose if it's not possible I'll just have to pass the variable and the variable's name as a string each time.

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  • Make jQuery-ui draggable handle cover entire page

    - by Acorn
    What would be the best way to make an element draggable when clicking anywhere in the window? Would I have to use a container <div> that covers the whole window? I tried making the body draggable but that didn't work. The problem with using a container <div> is that it moves and therefore doesn't cover the whole of the screen any more after it has been dragged. What about making a really vast container <div> that spans a large number of pixels in every direction so you would never get to the edge of it. Is that a bad idea? The idea (simplified) is to have a page with a square in the middle that can be dragged by dragging any part of the window. Here's a wonderfully unnecessary mockup :)

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  • Getting unpredictable data into a tabular format

    - by Acorn
    The situation: Each page I scrape has <input> elements with a title= and a value= I don't know what is going to be on the page. I want to have all my collected data in a single table at the end, with a column for each title. So basically, I need each row of data to line up with all the others, and if a row doesn't have a certain element, then it should be blank (but there must be something there to keep the alignment). eg. First page has: {animal: cat, colour: blue, fruit: lemon, day: monday} Second page has: {animal: fish, colour: green, day: saturday} Third page has: {animal: dog, number: 10, colour: yellow, fruit: mango, day: tuesday} Then my resulting table should be: animal | number | colour | fruit | day cat | none | blue | lemon | monday fish | none | green | none | saturday dog | 10 | yellow | mango | tuesday Although it would be good to keep the order of the title value pairs, which I know dictionaries wont do. So basically, I need to generate columns from all the titles (kept in order but somehow merged together) What would be the best way of going about this without knowing all the possible titles and explicitly specifying an order for the values to be put in?

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  • Global and local variables in my script

    - by Acorn
    I'm starting out learning javascript, and tried to write a little script that would make a grid of divs on a page. Here's the script: var tileWidth=50; var tileHeight=100; var leftPos=10; var topPos=10; var columns=10; var rows=10; var spacing=5; $('document').ready(function() { placeTiles(); }); function makeRow() { for (var i=0; i<columns; i++) { $('#canvas').append('<div class="tile" style="left:' + leftPos + 'px;top:' + topPos + 'px;"></div>'); var leftPos = leftPos + tileWidth + spacing; } } function placeTiles() { for (var i=0; i<rows; i++) { makeRow(); var topPos = topPos + tileHeight + spacing; } } At the moment, 100 <div>s get created, all with a top position of 10px and a left position of undefined (for the first <div> in the row) or NaN. What should I be doing differently? Why can't makerow() see my global leftPos variable (and all the other variables for that matter)? Thanks.

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  • Defining a class with specific style dynamically in jQuery

    - by Acorn
    Is it possible to define a class with specific style attributes dynamically with jQuery, rather than setting the style of all elements with that class? I could set the attributes of the class at the end of the script once all the elements have been created, but is that the best way to go about it? If I define the style of the class with $('.class').css('property','value'); at the beginning of the script, nothing would happen because the elements with class .class haven't been created yet, right?

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  • Get a CSS value from external style sheet with Javascript/jQuery

    - by Acorn
    Is it possible to get a value from the external CSS of a page if the element that the style refers to has not been generated yet? (the element is to be generated dynamically). The jQuery method I've seen is $('element').css('property','value');, but this relies on element being on the page. Is there a way of finding out what the property is set to within the CSS rather than the computed style of an element? Will I have to do something ugly like add a hidden copy of the element to my page so that I can access its style attributes?

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  • jQuery click event not working when mouse moves from one div to another with button held down

    - by Acorn
    I've made a page that uses jQuery to allow you to place <div>s on the page based on your mouse coordinates when you click. The page And here's the javascript: $('document').ready(function() { $("#canvas").click(function(e){ var x = e.pageX - this.offsetLeft; var y = e.pageY - this.offsetTop; $(document.createElement('div')).css({'left':x + 'px', 'top':y + 'px'}).addClass('tile').appendTo('#canvas'); }); }); I've found that if you mousedown in the div#canvas and mouseup with your pointer over a placed <div> (or vice versa) then a new <div> doesn't get placed. Why is this?

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  • Using mercurial for web-design version control (dealing with images)

    - by Acorn
    I'm very new to Version Control, and I was wondering if I could get some advice on how it can fit into website design. At the moment I'm working on a typical, simple website that includes images: A few .html files and a .css file One folder full of photographs Another folder with the corresponding thumbnails Can I just put the whole lot in a repository? Or is there a better way I could apply Version Control to it? How should I deal with the images? edit: How well will it work with changes to the images? What if I decide to try and optimise my photographs or resize them. I wont be able to see what exactly changed about the images, should comments be enough to keep track of that?

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  • Javascript/jQuery get external CSS value

    - by Acorn
    Is it possible to get a value from the external CSS of a page if the element that the style refers to has not been generated yet? (the element is to be generated dynamically). The jQuery method I've seen is $('element').css('property','value');, but this relies on element being on the page. Is there a way of finding out what the property is set to within the CSS rather than the computed style of an element?

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  • How to append() an element and set its style with css() at the same time with jQuery

    - by Acorn
    I tried: $('#canvas').append('<div class="tile"></div>').css({left: leftPos, top: topPos});, but that sets the style of #canvas rather than the appended element. I then tried: $('#canvas').append(('<div class="tile"></div>').css({left: leftPos, top: topPos}));, but that gives the error "Object <div class="tile"></div> has no method 'css'". How can I add the element and set its style at the same time?

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  • Finding out event that called a CGI script

    - by Acorn
    What I want is to be able to make my CGI script do different things depending on what action initiated the calling of the script. For example, if one button is pressed, a database is cleared. If another button is pressed, a form is submitted and that data is added to the database. Should I be doing something like adding the name of the form/button to the end of the POST data submitted in jQuery and then .poping it off in the script? Or is there some other data that's already sent in the POST that I could get from FieldStorage that would give me the information I need to decide what the script should do when it's called? And what if I wasn't using javascript? Would I have to have a hidden field that gets submitted with the name of the form/button? Or is it best to use a different target script for each button on a page?

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  • Stop an input field in a form from being submitted

    - by Acorn
    I'm writing some javascript that will insert some input fields into a form on a website. The thing is, I don't want those input fields to affect the form in any way, I don't want them to be submitted when the form is submitted, I only want my javascript to have access to their values. Is there some way I could add some input fields into the middle of a form and not have them submitted when the form is submitted? Obviously the ideal thing would be for the input fields to not be in the form element, but I want the layout of my resulting page to have my inserted input fields appear between elements of the original form.

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  • "Zooming" elements on a page while keeping the centre of enlargement in the centre of the window

    - by Acorn
    I'm trying to work out how to enlarge all elements on a page, but keep the centre of enlargement in the centre of the window. Example Page (up and down arrows to resize the image, you can also drag the image around) On this page, once the image reaches the top or the left side of the window the centre of enlargement changes. It also changes when you move the image. (exactly what you would expect) I'm thinking I'd need to take a completely different approach to achieve what I want. But I'm not sure what that approach is.. Any ideas?

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  • Et si Apple rachetait le fournisseur de puces de ses principaux concurrents ? L'hypothèse est sérieu

    Et si Apple rachetait ARM, le fournisseur de puces de ses concurrents ? L'hypothèse est sérieusement envisagée dans les milieux financiers Soyons clairs. Il s'agit d'une rumeur. Mais une rumeur persistante qui ne cesse de faire le tour de la City de Londres. Résultat, ce « bruit qui court » a fait bondir le cours d'ARM, la joint-venture fondée entre Acorn Computers, Apple et VLSI Technology, de +8 points en une seule et unique journée. ARM est la holding qui possède la technologie des célèbres puces qui équipent les teminaux de Nokia, Samsung, HTC (avec lequel il est en procès), la Nintendo DS ou encore la PSP de Sony (pour ne citer que ceux-ci). Bref, autant de concurrents...

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