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Fastest way to find the largest power of 10 smaller than x

由 独自空忆成欢 提交于 2019-12-09 11:35:18
问题 Is there any fast way to find the largest power of 10 smaller than a given number? I'm using this algorithm, at the moment, but something inside myself dies anytime I see it: 10**( int( math.log10(x) ) ) # python pow( 10, (int) log10(x) ) // C I could implement simple log10 and pow functions for my problems with one loop each, but still I'm wondering if there is some bit magic for decimal numbers. 回答1: An alternative algorithm is: i = 1; while((i * 10) < x) i *= 10; 回答2: Log and power are

How do I pass variables to all templates in django? [duplicate]

由 戏子无情 提交于 2019-12-09 09:28:40
问题 This question already has answers here : Django - How to make a variable available to all templates? (2 answers) Closed 3 years ago . I am trying to pass variables (browser variable) to all my templates in my app. Any advice on how to get it to work? View: def browser(request): primary_cat_list = Categories.objects.order_by("category") subcat_list = SubCategories.objects.order_by("sub_category") product = Productbackup.objects.order_by("website") browser = list(chain(primary_cat_list, subcat

C++ inherited class has member of same name

由 天涯浪子 提交于 2019-12-08 14:47:02
问题 In C++ you can put a member in a base class and a member with the same name in the inherited class. How can I access a specific one in the inherited class? 回答1: In that case you should fully qualify a member name. class A { public: int x; }; class B : public A { public: int x; B() { x = 0; A::x = 1; } }; 回答2: If you specify the name you'll access the one in the inherited class automatically. If you mean how do you access the one in the base class, use Base::member 回答3: To access the hidden

libevne核心-event_base

由 半腔热情 提交于 2019-12-08 14:24:24
1.生成一个event_base 在使用其他的libevent函数之前，你必须要先分配一个 event_base 结构， event_base 结构持有 event集合并且能判断那个event是活跃的。 如果 event_base 被设置为使用locking，那么它在多线程内访问是安全的。但是它的loop只能在 一个线程内执行。如果想要多个线程都能polling，就需要每个线程一个 event_base 结构。 每个 event_base 都有一个method（或者backend），用于判断event就绪。这些method有： 1.select 2.poll 3.epoll 3.kqueue 4.devpoll 5.evport 6.win32 你可以用环境变量来disable特定的backend，如果你想关闭kqueue,那么设置 EVENT_NOKQUEUE 环境 变量，或者使用函数 event_config_avoid_method() 。 2.设置一个默认的event_base event_base_new() 分配并返回一个默认设置的 event_base ,如果出错，它返回NULL。 它会选择操作系统支持的最快的method最为自己的method。 接口: #include<event2/event.h> struct event_base* event_base

Base Address of Memory Object OpenCL

由 梦想的初衷 提交于 2019-12-08 13:17:14
问题 I want to traverse a tree at GPU with OpenCL , so i assemble the tree in a contiguous block at host and i change the addresses of all pointers so as to be consistent at device as follows: TreeAddressDevice = (size_t)BaseAddressDevice + ((size_t)TreeAddressHost - (size_t)BaseAddressHost); I want the base address of the memory buffer : At host i allocate memory for the buffer, as follows: cl_mem tree_d = clCreateBuffer(...); The problem is that cl_mems are objects that track an internal

C# - when to call base.OnSomething?

由 |▌冷眼眸甩不掉的悲伤 提交于 2019-12-08 07:53:23
问题 I'm using Windows.Forms and have to inherit some controls to provide custom behavior. This inheritance obviously leads to method overriding. So, here is the question - in which cases the order of calling base.OnSomething(...) can really affect the visible behavior of your program? protected override OnRetrieveVirtualItem(RetrieveVirtualItemEventArgs e) { // base.OnRetrieveVirtualItem(e); - Could this potentially break something? // Perform your custom method. // ... base.OnRetrieveVirtualItem

How to generate all possible combinations of N slots with V possible values? [duplicate]

由 梦想的初衷 提交于 2019-12-08 03:22:21
问题 This question already has answers here : Is there an algorithm to find unique combinations of 2 lists? 5 lists? (7 answers) Number permutations in python iterative (3 answers) In Python, is there a concise way to use a list comprehension with multiple iterators? (4 answers) Generating all possibly length n combinations of two items in python (2 answers) Closed last year . I have N ordered slots. Each slot has a value within V possible values N = 4 # number of objects (e.g. slots) possible

How To: add dynamically HiddenField in masterpage base page

由 淺唱寂寞╮ 提交于 2019-12-08 02:20:31
问题 I have a Base MasterPage class, from which my masterpages will inherit. I have some javascript functions there for it's child pages to include. As it's a base class, it does not have a visual designer nor I can add XHTML code. I need to add a hidden field to the class so I can set it's value in the javascript code, and when a postback occurs I can get the setted value on my content pages. Yet I fail to achieve this, for when I try to add the hidden field to the base masterpage's control

libevent笔记4：Filter_bufferevent过滤器

由 大憨熊 提交于 2019-12-08 00:21:24
Filter_bufferevent是一种基于bufferevent的过滤器，其本身也是一个bufferevent。能够对底层bufferevent输入缓存区中的数据进行操作（加/解密等）后再读取，同样也能在一定的操作后再将数据写入底层bufferevent的输出缓存区。需要注意的是，在创建Filter_bufferevent后，底层bufferevent的读写回调函数就不会再生效了，而缓存区的回调函数依旧有效。 Filter_bufferevent相关函数 struct bufferevent bufferevent_filter_new (struct bufferevent underlying, bufferevent_filter_cb input_filter, bufferevent_filter_cb output_filter, int options, void( free_context)(void ), void *ctx)：创建一个过滤器，参数列表如下： struct bufferevent *underlying：需要过滤的底层bufferevent； bufferevent_filter_cb input_filter/bufferevent_filter_cb output_filter：对底层bufferevent的输入

Convert a decimal number that is not integer to base 4 in Matlab?

由 好久不见. 提交于 2019-12-07 21:24:04
问题 Is there a way to convert a decimal number between $0$ and $1$ that is not integer to base 4 in Matlab? E.g. if I put 2/5 I want to get 0.12121212... (with some approximation I guess) The function dec2base only works for integers. 回答1: Listed in this post is a vectorized approach that works through all possible combinations of digits to select the best one for the final output as a string. Please note that because of its very nature of creating all possible combinations, it would be memory
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