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谷歌在这个问题上保持沉默。我目前在 Matlab 中仅在 16 位有符号定点上实现数值计算器。但是对 16 位定点的算术运算导致数据类型扩展为以下

>> a = int16(1.5 * 4)
a = 6
>> T = numerictype(1, 16, 2)

T = DataTypeMode: Fixed-point: binary point scaling
            Signedness: Signed
            WordLength: 16
        FractionLength: 2
>> dis = reinterpretcast(a, T)

dis = 1.5000

          DataTypeMode: Fixed-point: binary point scaling
            Signedness: Signed
            WordLength: 16
        FractionLength: 2
>> c = dis * dis

c = 2.2500

          DataTypeMode: Fixed-point: binary point scaling
            Signedness: Signed
            WordLength: 32
        FractionLength: 4

我希望变量c保持在 WordLength 16，FractionLength 2。是否可以在不扩展基础数据类型的情况下完成 16 位定点上的算术运算？我将承担任何上溢和下溢的风险。任何帮助都是极好的。

编辑：输入fimath命令窗口会导致错误。为什么会出现这个错误？

>> F = fimath('OverflowAction','Wrap', 'RoundingMethod', 'Floor', ...
           'ProductWordLength', 16, 'ProductFractionLength', 2);
No public field OverflowAction exists for class embedded.fimath.

Error in fimath (line 72)
  this.(varargin{k}) = varargin{k+1};
4

1 回答 1

5

本地解决方案： 您可以使用fimath对象来指定产品结果的精度：

F = fimath('OverflowMode','Wrap', 'RoundMode', 'Floor', ...
           'ProductMode', 'SpecifyPrecision', ...
           'ProductWordLength', 16, 'ProductFractionLength', 2);
dis.fimath = F;

那么结果将是：

>> dis*dis
ans =
         2.25

          DataTypeMode: Fixed-point: binary point scaling
            Signedness: Signed
            WordLength: 16
        FractionLength: 2

             RoundMode: floor
          OverflowMode: wrap
           ProductMode: SpecifyPrecision
     ProductWordLength: 16
 ProductFractionLength: 2
               SumMode: FullPrecision
      MaxSumWordLength: 128

全局解决方案：或者，如果您希望将其应用于您可以使用的所有定点变量

globalfimath('OverflowMode','Wrap', 'RoundMode', 'Floor', ...
             'ProductMode', 'SpecifyPrecision', ...
             'ProductWordLength', 16, 'ProductFractionLength', 2);

请注意，要限制为 16 位，您还需要指定 sum 的精度（使用SumMode和SumWordLength的属性fimath），否则 sum 的字长为 17：

>> dis+dis
ans =
     3

          DataTypeMode: Fixed-point: binary point scaling
            Signedness: Signed
            WordLength: 17
        FractionLength: 2
于 2013-09-25T11:44:10.447 回答