favicon – In , is the sizes attribute required or optional?

I note that in the WHAT-WG section on:

link rel="icon"

Every icon referenced includes a sizes attribute:

<link rel=icon href=favicon.png sizes="16x16" type="image/png">
<link rel=icon href=windows.ico sizes="32x32 48x48" type="image/vnd.microsoft.icon">
<link rel=icon href=mac.icns sizes="128x128 512x512 8192x8192 32768x32768">
<link rel=icon href=iphone.png sizes="57x57" type="image/png">
<link rel=icon href=gnome.svg sizes="any" type="image/svg+xml">
<link rel=stylesheet href=lsforums.css>

Source: https://html.spec.whatwg.org/dev/links.html#rel-icon

But, to my knowledge, the sizes attribute has never been compulsory.

However, now that I’m trying to find an authoritative source confirming the sizes attribute is optional, I cannot.

In <link rel="icon">, is the sizes attribute required or optional?

I am specifically looking for an authoritative source – thanks.

Plotting a well defined function displays nothing for two-thirds of the range required

The plot in question concerns the second derivative of an inverse Laplace transform (ILT) of a function with five parameters. Here is the ILT

prod = (s - cr1) (s - cr2) (s - cr3) (s - cr4);
LW = (1 + s)^2/(si prod);
Print("symbolic W'=", Wp = D(InverseLaplaceTransform(LW, s, x), x))

Four parameters are functions of the fifth parameter “si”, defined as the roots of a fourth order equation

cr = {cr1, cr2, cr3, cr4} = 
   s /. Solve(si s^2 + 107 s/5 + 10 ((1 + s)^(-2) - 1) - 1/10 == 0, 

Plotting the first derivative of the ILT takes .64

lx = 13; Timing(
 pd = Plot(Evaluate(Wp /. si -> 1), {x, 0, lx}, 
   PlotRange -> {{0, lx}, {0.0225, .0275}}))

Plotting of the second derivative of the ILT takes 14.84 and displays nothing for two-thirds of the range lx

    Wd = D(Wp, x);
Timing(Plot((Wd /. si -> 1), {x, 0, lx}, 
 PlotRange -> {{0, lx}, {-0.002, .002}}))

kvm virtualization – How much disk space is required to install KVM hypervisor on a CentOS machine?

If you want to install KVM, QEMU, libvirt, virt-manager, your available space is more than enough. The absolute minimum is KVM and QEMU which take very little space.
If you want to install oVirt, a vSphere or MS SCVMM like web console, you can also proceed, but probably you’ll soon need more space – it also needs a DB backend.

But you should be careful regarding the locations of VMs – virtual disks and ISOs, that’s the ones taking space. Probably you’ll have to change the default location of the libraries.

database design – MS ACCESS : On a subject form, how can I highlight a required control IF AND ONLY IF the user misses it (an error is thrown)

I have built a subject form and would like to find a way to highlight a textbox control that is required (it is paired to a required field) IF AND ONLY IF the user fails to enter it. I know that there are validation rules that are built as part of the subject table that will give the user an indication of an error when they fail to enter required data. But, I am looking for a more “colorful” or “visual” indication, so to speak. I have seen people simply give a colorful border to a required field. This is fine, but I am trying to find a way to either highlight or make a colorful border on the required control IF AND ONLY IF an error is thrown.

I hope my question is clear. This is my first question on here so I apologize if it’s messy. I am using ACCESS 2016

posts – How to make Feature Image required for a Particular Template

For a particular post, I use a specific template (Story template) to display it. And any post with this particular template should have Featured Image.

I am using this snippet code to check if the item to be published is a post or a page. I would want to include if the user selects the template (Story template), s/he would need to add a featured image else the post would not be published.

add_action('save_story_post', 'check_featured_image');
add_action('admin_notices', 'featured_image_error');
function check_featured_image($post_id) {
    // Check if it is a post
    if(get_post_type($post_id) != 'post')
    if ( !has_post_thumbnail( $post_id ) ) {
        // set a transient to show the users an admin message
        set_transient( "has_post_thumbnail", "no" );
        // unhook this function so it doesn't loop infinitely
        remove_action('save_post', 'check_featured_image');
        // update the post set it to draft
        wp_update_post(array('ID' => $post_id, 'post_status' => 'draft'));
        add_action('save_post', 'check_featured_image');
    } else {
        delete_transient( "has_post_thumbnail" );
function featured_image_error()
    // check if the transient is set, and display the error message
    if ( get_transient( "has_post_thumbnail" ) == "no" ) {
        echo "&lt;div id='message' class='error'&gt;&lt;p&gt;&lt;strong&gt;You must select Featured Image. Your Post is saved but it can not be published.&lt;/strong&gt;&lt;/p&gt;&lt;/div&gt;";
        delete_transient( "has_post_thumbnail" );

dynamic programming – Speeding up the Rummikub algorithm – explanation required

Regarding this question: Rummikub algorithm.

I was reading the first part of the solution in the posted answer (specifically, when there are no jokers involved, all tiles are distinct and only four colours are involved). Then, I reached the part in which the says that the algorithm runs in $O(ABCD(A+B+C+D))$ time, which is easy to determine why.

However, he the goes on to saying that we can speed up the algorithm so as to run in $O(ABCD)$ time by changing
“the recurrence to ensure this occurs only once while maintaining correctness, which leads to $O(1)$ time for every ‘cell’ in the DP-table”.

My problem is: I do not see how this can be done. I have tried playing around a bit with the recurrence, but I do not see how it can be modified, or what else we should keep track of so that we can speed up the time.



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distributed systems – Why is the ‘Integrity’ property required in consensus protocols?

Formally a consensus protocol must satisfy the following three properties:


  • Eventually, every correct process decides some value.


  • If all the correct processes proposed the same value “v”, then any correct process must decide “v”.


  • Every correct process must agree on the same value.

“Termination” certifies the protocol is resilient to halting failures. “Agreement” deters any two correct processes from deciding on different values which would break consensus. But what about “Integrity”, why is it required? If all correct processes propose “x” but then they all decide “y” (e.g. f(x) = y), is that a violation of consensus?

magento2.3 – Translate *Required Fields – Magento 2.3

We have an issue that we are not able to translate “*Required Field” and “This is a Required field”

I also notice that the previous developer have put the Norwegian Language pack under /vendor/magento2translations. I would like to think it should be under app/i18n/magento2translations (create this path ofc.

The owner told me they have used translateline to translate everything on the web page, as in manually. Shouldn’t the translate pack do this for them? except if there is any specific translation? We also have problems where we are able to translate via translateline but will not save after we put the site back to production mode.

Another question, do i need to set the i18n/no/NO on every module i have, or have does this work?

Any help is appreciated

Is UK transit visa required for a permanent resident in Schengen?

I have a permanent residence card from a Schengen country. Do I need any visa to arrive at Heathrow and transit to a SAS flight? From the rules I read at gov.uk, there is a line in exceptions saying:

“a common format residence permit issued by an European Economic Area
(EEA) country or Switzerland”

The wording confuses me a bit. So asking to double check. Thanks