机器学习 梯度下降

machine learning gradient descent

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Embedded System interview Question

1. What are static variables? Static variable in a function only remain one copy of itself. Static variable in a module can be used by any function in the module Static function can only be called in its class 2.  What are volatile variables? Volatile variables may change its value unexpectedly in the program. The program will check its value every time, it tries to use it. If a variable is not volatile, the program may keep a copy of the var in its cache. 3. What do you mean by const keyword ? A constant variable is a read only variable. You cant change its value else where except initialization. 4. What is interrupt latency? Interrupt latency is the time between the generation of interrupt and the time for interrupt  handler  to process it. 5. How you can optimize it? We may use polling and message passing for interrupt to handle interrupt immediately. 6. What is size of character, integer, integer pointer, character pointer? The size of character i...
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MicroKernel & Exokernel 操作系统未来可能的发展

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MicroKernel  可以叫做微内核，有人认为传统的monolithic kernel 提供的东西太多，我们可以给内核减负。 最典型的例子就是L4 micro kernel (图中的kernel)只提供最简单的服务，比如IPC (inter process communication), scheduling, address space  剩下的都交给Server 去处理，Server 类似于传统的monolithic kernel 比如Linux, 但是需要改动,L4 把它改为L4Linux. 源代码修改，此外他们还修改了Windows XP (windows 并非完全的不开源，在授权的情况下可以看到源代码). 修改的目的，很简单：以前Server talks to hardware directly, 现在多加了一层 Kernel (L4),它处理所有的hardware interrupt, 然后作为message 传递给server, server 再传递给software. 比如浏览器process 需要一个network packet。 收到packet 以后,L4 作出interrupt,传给Server(比如L4Linux),Server 再与L4,通过IPC 请求packet内容，L4会map到L4Linux的address space，Server 再传给Software(e.g. Firefox).  再比如page fault（由于内存容量有限，有些内容被暂时swap 到硬盘，application 想用的时候发现不在了，就产生page fault） 产生,首先处理interrupt的是Kernel, Kernel sends IPC to L4Linux, L4Linux从自己manage的physical memory 里面分一个page出来，给application,并更新自己的shadow page table(不是真正的page table) .L4Linux 产生一个返回值告诉L4, 已经完成。L4 updates its true hardware page table. Micro Kernel 从设计之初的想法应该是高效的，反映速度快，因为很多东西都由u...
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Embedded systems interview questions

6. Difference between object oriented and object based languages?       Object oriented means everything is an object, they could have all the features of object such as inheritance, implementation of interface. But object based lang means it only uses object idea, it may not let you to create your own object. 7. Multiple inheritance - objects contain howmany multiply inherited ancestor?     Java allows only one inheritance, but lang such as C++ allows multiple inheritance which means one class could inherit the behavior on many parent classes. 10.Is java a pure object oriented language? Why?       Java is not pure OOL, it still maintains some primitives such as int, char 11. Order of constructor and destructor call in case of multiple inheritance     The order of constructor is from base to current which means the constructor of the parent class will be called first, which is the opposite for destructor. ...
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