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  • I'm trying to understand why we use generate in verilog along with a for loop.Using a generate and for loop together:reg [3:0] temp; genvar i; generate for (i = 0; i < 3 ; i = i + 1) begin: ...

    I'm trying to understand why we use generate in verilog along with a for loop.

    Using a generate and for loop together:

    reg [3:0] temp;
    genvar i;
    generate
    for (i = 0; i < 3 ; i = i + 1) begin: 
        always @(posedge sysclk) begin
            temp[i] <= 1'b0;
        end
    end
    endgenerate
    

    Using only for loop:

    reg [3:0] temp;
    genvar i;
    always @(posedge sysclk) begin
      for (i = 0; i < 3 ; i = i + 1) begin: 
        temp[i] <= 1'b0;
        end
    end
    

    I'm considering the two snippets would basically produce the same result i.e. temp[0] to temp[10] equal to value 0. What is the difference/advantage we see by using a generate statement in this case ?


    Answer1:

    In general, the main difference between generate for loop and regular for loop is that the generate for loop is generating an instance for each iteration. Meaning that in your example there will be 3 always blocks (as opposed to 1 block in the regular loop case).

    A good example of code that requires generate for is:

    module A();
    ..
    endmodule;
    
    module B();
    parameter NUM_OF_A_MODULES = 2; // should be overriden from higher hierarchy
    genvar i;
    for (i=0 i<NUM_OF_A_MODULES; i=i+1) {
      A A_inst();
    }
    endmodule;
    

    In this example a regular for cannot do the work of creating NUM_OF_A_MODULES instances.

    In your example, you can acheive the required result in both ways. (as long as you fix some minor bugs :) )


    Answer2:

    Generate blocks are useful when change the physical structure of then module via parameters. For example choosing negedge or posedge clock and only enabling one:

    if ( param_use_pos == 1) begin : use_pos
      always @(posedge sysclk) begin
        ...
      end
    end
    else begin : use_neg
      always @(negedge sysclk) begin
         ...
      end
    end
    

    If you are not changing the physical structure, it is typically better to use for loops and if-else statements inside the always block. Both approaches can synthesize the same but when running RTL simulation the non-generate block approach will typically simulate faster. This is because simulators normally can process a single N-bit operation faster than N 1-bit operations. Again synthesis is the same result

    // faster :: 1 always block, simulator can optimize the for loop
    always @(posedge sysclk) begin 
      for (i = 0; i < 3 ; i = i + 1) begin
        temp[i] <= 1'b0;
      end
    end
    
    // slower :: creates 4 always blocks, harder for the simulator to optimize
    genvar i;
    generate // optional if > *-2001
    for (i = 0; i < 3 ; i = i + 1) begin 
        always @(posedge sysclk) begin
            temp[i] <= 1'b0;
        end
    end
    endgenerate // match generate


    展开全文
  • https://www.pythoncentral.io/how-to-use-pythons-xrange-and-range/ xrange() 函数用法与 range 完全相同,所不同是生成不是一个数组,而是一个生成器。 ... ...
    
    

    xrange() 函数用法与 range 完全相同,所不同的是生成的不是一个数组,而是一个生成器。
    http://www.runoob.com/python/python-func-xrange.html

    展开全文
  • make cmake 的区别

    2019-08-12 16:58:48
    make cmake 的区别学习 博客 博客地址:IT老兵驿站 正文 “The build process has one step if you use a Makefile, namely typing “make” at the command line. For CMake, there are two steps: First, you...

    概要

    make 和 cmake 的区别学习

    博客

    博客地址:IT老兵驿站

    正文

    “The build process has one step if you use a Makefile, namely typing “make” at the command line. For CMake, there are two steps: First, you need to setup your build environment (either by typing cmake <source_dir> in your build directory or by running some GUI client). This creates a makefile or something equivalent, depending on the build system of your choice (e.g. Make on *nix, VC++ or MinGW on Windows, etc). The build system can be passed to CMake as a parameter. However, CMake makes reasonable default choices depending on your system configuration. Second, you perform the actual build in the selected build system.”

    参考上文所说,cmake 是两步,通过执行cmake <source_dir>(根据CMakeLists.txt文件的配置), 先根据环境生成 Makefile 文件,然后正常使用 make 去进行编译。

    传统的make,我这里的理解是通过configure去扫描软件的依赖,然后根据Makefile.in(往往是通过automake等工具所生成的),生成Makefile

    cmake更多是帮助进行跨平台的编译。

    初步理解是这样,等待以后来完善。

    参考

    https://www.quora.com/What-is-the-difference-between-CMake-and-make
    https://prateekvjoshi.com/2014/02/01/cmake-vs-make/

    展开全文
  • is==的区别解释1 == is for value equality. Use it when you would like to know if two objects have the same value. is is for reference equality. Use it when you would like to know if two references ...

    is和==的区别

    解释1

    • == is for value equality. Use it when you would like to know if two objects have the same value.
    • is is for reference equality. Use it when you would like to know if two references refer to the same object.

    解释2

    • is: if two variables point to the same object.
    • ==: if the objects referred to by the variables are equal.

    解释3

    python中的每个对象都有三种属性:id, value, type. 不同对象实例的id一定是不同的,可以把id看做是和内存地址一一对应的。而value只是检查两个变量的内容是否相等。

    解释4

    == 会调用对应类里的__eq__()函数。例如:

    class Name(object):
        def __eq__(self, other):
            print('__eq__() is called.')
    name1 = Name()
    name2 = Name()
    print(name1  == name2)

    结果:

    __eq__() is called.
    None    # __eq__()里面没有return,所以==的结果为None

    然而如果没有重写__eq__()函数,我猜测就会去调用is的操作。例如:

    class Name(object):
        pass
    
    # 创建两个不同的Name对象
    name1 = Name()  
    name2 = Name()
    # 让name3和name1指向同一个Name对象
    name3 = name1
    
    print(name1 is name2, name1  == name2)
    print(name1 is name3, name1  == name3)

    结果:

    False False
    True True

    例外情况:

    This is inconsistent with the earlier result. It turns out the reference implementation of Python caches integer objects in the range -5~256 as singleton instances for performance reasons.

    Example:

    for i in range(1, 10):
        a = -i
        is_res = a is int(str(a))
        print("%i: %s" % (a, is_res))
    
    print()
    
    for i in range(250, 260):
        a = i
        is_res = a is int(str(a))
        print("%i: %s" % (a, is_res))

    results:

    -1: True
    -2: True
    -3: True
    -4: True
    -5: True
    -6: False
    -7: False
    -8: False
    -9: False
    
    250: True
    251: True
    252: True
    253: True
    254: True
    255: True
    256: True
    257: False
    258: False
    259: False

    参考:Is there a difference between == and is in Python?

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  • BufferCache的区别

    2012-11-10 10:17:37
    A buffer is something that has yet to be "written" to disk. A cache is something that has been "read" from the disk and stored for later use.
  • $ORACLE_BASE$ORACLE_HOME 的区别 $ORACLE_BASE for installation purpose only. oracle will use it to determine the optimal disk structure (oradata oraInventory product etc). it's optional. $ORACLE_H...
  • mysql5.6mysql5.7分配undo回滚段的区别

    千次阅读 2015-08-31 22:22:31
    1、mysql5.7中分为2类:临时表空间回滚段普通回滚段。...MySQL 5.7.2, 32 undo logs are reserved for use by temporary tables and are hosted in the temporary table tablespace (ibtmp1). To allocat
  • using System; using System.ComponentModel; // The following example demonstrates how to use the // GC.SuppressFinalize method in a resource class to prevent // the clean-up code for th...
  • 迷你5迷你4区别So you want to display a Sparkline? There’s no need to use bulky libraries, especially those built on top of D3 (don’t get me wrong, many of them are great), or pay for a commercial ...
  • Vim emacs的区别

    千次阅读 2014-02-11 07:47:08
    1. With Emacs you are expected to have it open 24/7 and live inside the program, almost everything you do can be done from there. You write your own extensions, use it for note taking, organisation
  • <p>I'm a newbie on Golang and I just learnt about the conception... So I just want to know what is exactly the difference between them, why doesn't Go use the routine instead of multi-thread? </div>
  • cachebuffer的区别

    2014-02-10 14:34:00
    A buffer is just a container to hold data for a short period of time when more comes in at any given time than a consumer can use / process. It's a first-in, first-out situation - the data comes in,.....
  • FragmentPagerAdapter官方解释...This version of the pager is best for use when there are a handful of typically more static fragments to be paged through, such as a set of tabs. The fragment of each p...
  • JSONObject中optStringgetString等的区别

    千次阅读 2017-06-03 14:29:49
    The difference is that optString returns the empty string ("") if the key you specify doesn't exist.getString on the other hand throws a JSONException.... it's an error for the data to
  • KVO vs NSNotification vs protocol/delegate: ...1. Use a delegate if you want to talk to only one object. For example, a tableView has a delegate - only one object should be responsible for dealing with
  • 基本所有公司编程规范都有如下规定 Spaces vs. Tabs Use only spaces, and indent 2 ...We use spaces for indentation. Do not use tabs in your code. You should set your editor to emit spaces when you hit
  • tomcat中Catalina里JAVA_OPTSCATALINA_OPTS区别 export JAVA_OPTS="-Dfile.encoding=utf-8" If you start Tomcat after exporting JAVA_OPTS, it will make sure to use UTF-8 encoding for all ...
  • 基本所有公司编程规范都有如下规定 Spaces vs. Tabs Use only spaces, and indent 2 ... We use spaces for indentation. Do not use tabs in your code. You should set your editor to emit spaces when
  • R 语言中1 1L的区别

    千次阅读 2019-06-09 23:10:36
    To explicitly create an integer value for a constant you can call the function as.integer or more simply use "L " suffix. 数字后面, 加上L, 表明他是整数, 运算速度更快, 占用内存更小...
  • Jquery.ajax()中的参数typemethod的区别

    万次阅读 2018-11-30 20:51:16
    You should use type if you’re using versions of jQuery prior to 1.9.0. 即typemethod是一样。只不过是1.9.0版本出method 估计是让程序员更好记,更符合习惯吧。(个人也是认为meth...
  • A buffer is something that has yet to be "written" to disk. A cache issomething that has been "read" from the disk and stored for later use.
  • 在使用VS2013时报错 fopenfopen_s的区别 Consider using fopen_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details. fopen函数: 原型:FILE * fopen(const char * ...
  • For example, I tried to create a list of functions, like this, but it didn’t work: <pre><code>> (define math-fns '(+ - * /)) > (map (lambda (fn) (fn 1)) math-fns) application: not a procedure...

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for和useto的区别use