如何在MATLAB中知道变量的大小

我在MATLAB中有变量，我用

class（）

检查了它们的类，但我也想知道它们在内存中的大小。更准确地说，我知道它们是双精度类型，我想确保它们是32位双精度而不是64位

我使用的MATLAB版本是R2009b。

您可以使用它来获得一组结构，其中包括描述每个变量的字节大小

---

注意，根据定义，double是64位的

我编写了一个简单的便利函数来处理这个问题。用途是：

>> x = ones(1000);
>> ByteSize(x)
7.63 Mb

我运行R2007a，因此Java对象不返回大小的问题可能已在后续版本中得到解决。代码如下：

function ByteSize(in, fid)
% BYTESIZE writes the memory usage of the provide variable to the given file
% identifier. Output is written to screen if fid is 1, empty or not provided.

if nargin == 1 || isempty(fid)
    fid = 1;
end

s = whos('in');
fprintf(fid,[Bytes2str(s.bytes) '\n']);
end

function str = Bytes2str(NumBytes)
% BYTES2STR Private function to take integer bytes and convert it to
% scale-appropriate size.

scale = floor(log(NumBytes)/log(1024));
switch scale
    case 0
        str = [sprintf('%.0f',NumBytes) ' b'];
    case 1
        str = [sprintf('%.2f',NumBytes/(1024)) ' kb'];
    case 2
        str = [sprintf('%.2f',NumBytes/(1024^2)) ' Mb'];
    case 3
        str = [sprintf('%.2f',NumBytes/(1024^3)) ' Gb'];
    case 4
        str = [sprintf('%.2f',NumBytes/(1024^4)) ' Tb'];
    case -inf
        % Size occasionally returned as zero (eg some Java objects).
        str = 'Not Available';
    otherwise
       str = 'Over a petabyte!!!';
end
end

function b = getByteSize(theVariable, returnType, fid)
% getByteSize returns the mem.usage of the provided variable(theVariable) to the given file
% identifier. 
% returnType is assigned meaningfully according to the byte size if not stated
% Output is written to screen if fid is 1, empty or not provided.
s = whos('theVariable');
b = s.bytes;
if nargin == 1 || isempty(returnType)
    scale = floor(log(b)/log(1024));
    switch scale
        case 0
            returnType = 'byte';
        case 1
            returnType = 'kb';
        case 2
            returnType = 'mb';
        case 3
            returnType = 'gb';
        case 4
            returnType = 'tb';
        case -inf
            % Size occasionally returned as zero (eg some Java objects).
            returnType = 'byte';
            warning('Size occasionally returned as zero (eg some Java objects). Bytes assumed');
        otherwise
            returnType = 'petabytes';
            warning('Over 1024 petabyte. petabytes assumed');
    end
end
switch returnType
    case {'b','byte','bytes'}
        b = s.bytes;
    case {'kb','kbs','kilobyte','kilobytes'}
        b = b / 1024;
    case {'mb','mbs','megabyte','megabytes'}
        b = b / 1024^2;
    case {'gb','gbs','gigabyte','gigabytes'}
        b = b / 1024^3;
    case {'tb','tbs','terabyte','terabytes'}
        b = b / 1024^4;
    case {'pb','pbs','petabyte','petabytes'}
        b = b / 1024^5;
    otherwise
        returnType = 'bytes';
end
if nargin <= 2 || isempty(fid) || fid == 1
    fprintf(1,[num2str(b) ' ' returnType '\n']);
elseif nargin > 2 && ~isempty(fid) && fid > 2
    try
        fprintf(fid,[num2str(b) ' ' returnType '\n']);
    catch
        warning(['fid(' num2str(fid) ') could not be edited. Hence the output will be written on the screen.']);
        fprintf(1,[num2str(b) ' ' returnType '\n']);
    end
end
end

---

这将为您提供以MB为单位的大小，例如MB=123.78

我尝试增强“MatlabSorter”的简单功能来处理此问题。用法仍然相同：

>> x = ones(1000);
>> getByteSize(x)
7.63 mb

补充：

1.您可以说明您寻求的返回类型-b、kb、mb、tb或pb

2.无需在屏幕上打印即可将结果作为变量获得

代码如下：

function ByteSize(in, fid)
% BYTESIZE writes the memory usage of the provide variable to the given file
% identifier. Output is written to screen if fid is 1, empty or not provided.

if nargin == 1 || isempty(fid)
    fid = 1;
end

s = whos('in');
fprintf(fid,[Bytes2str(s.bytes) '\n']);
end

function str = Bytes2str(NumBytes)
% BYTES2STR Private function to take integer bytes and convert it to
% scale-appropriate size.

scale = floor(log(NumBytes)/log(1024));
switch scale
    case 0
        str = [sprintf('%.0f',NumBytes) ' b'];
    case 1
        str = [sprintf('%.2f',NumBytes/(1024)) ' kb'];
    case 2
        str = [sprintf('%.2f',NumBytes/(1024^2)) ' Mb'];
    case 3
        str = [sprintf('%.2f',NumBytes/(1024^3)) ' Gb'];
    case 4
        str = [sprintf('%.2f',NumBytes/(1024^4)) ' Tb'];
    case -inf
        % Size occasionally returned as zero (eg some Java objects).
        str = 'Not Available';
    otherwise
       str = 'Over a petabyte!!!';
end
end

function b = getByteSize(theVariable, returnType, fid)
% getByteSize returns the mem.usage of the provided variable(theVariable) to the given file
% identifier. 
% returnType is assigned meaningfully according to the byte size if not stated
% Output is written to screen if fid is 1, empty or not provided.
s = whos('theVariable');
b = s.bytes;
if nargin == 1 || isempty(returnType)
    scale = floor(log(b)/log(1024));
    switch scale
        case 0
            returnType = 'byte';
        case 1
            returnType = 'kb';
        case 2
            returnType = 'mb';
        case 3
            returnType = 'gb';
        case 4
            returnType = 'tb';
        case -inf
            % Size occasionally returned as zero (eg some Java objects).
            returnType = 'byte';
            warning('Size occasionally returned as zero (eg some Java objects). Bytes assumed');
        otherwise
            returnType = 'petabytes';
            warning('Over 1024 petabyte. petabytes assumed');
    end
end
switch returnType
    case {'b','byte','bytes'}
        b = s.bytes;
    case {'kb','kbs','kilobyte','kilobytes'}
        b = b / 1024;
    case {'mb','mbs','megabyte','megabytes'}
        b = b / 1024^2;
    case {'gb','gbs','gigabyte','gigabytes'}
        b = b / 1024^3;
    case {'tb','tbs','terabyte','terabytes'}
        b = b / 1024^4;
    case {'pb','pbs','petabyte','petabytes'}
        b = b / 1024^5;
    otherwise
        returnType = 'bytes';
end
if nargin <= 2 || isempty(fid) || fid == 1
    fprintf(1,[num2str(b) ' ' returnType '\n']);
elseif nargin > 2 && ~isempty(fid) && fid > 2
    try
        fprintf(fid,[num2str(b) ' ' returnType '\n']);
    catch
        warning(['fid(' num2str(fid) ') could not be edited. Hence the output will be written on the screen.']);
        fprintf(1,[num2str(b) ' ' returnType '\n']);
    end
end
end

函数b=getByteSize（变量，返回类型，fid）
%getByteSize将所提供变量（变量）的mem.usage返回给给定文件
%标识符。
%如果未说明，则根据字节大小有意义地分配returnType
%如果fid为1、为空或未提供，则输出写入屏幕。
s=whos（“变量”）；
b＝s字节；
如果nargin==1 | |为空（returnType）
刻度=地板（对数（b）/对数（1024））；
开关秤
案例0
returnType='byte'；
案例1
returnType='kb'；
案例2
returnType='mb'；
案例3
returnType='gb'；
案例4
returnType='tb'；
case-inf
%大小偶尔返回为零（例如一些Java对象）。
returnType='byte'；
警告（'大小偶尔返回为零（例如一些Java对象）。假定为字节'）；
否则
returnType='petabytes'；
警告（“假定超过1024 PB.PB”）；
结束
结束
开关返回式
大小写{b'，byte'，bytes}
b＝s字节；
大小写{'kb'，'kbs'，'kb'，'kb'}
b=b/1024；
大小写{'mb'，'mbs'，'mb'，'mb'}
b=b/1024^2；
大小写{gb'，gbs'，gb'，gb}
b=b/1024^3；
大小写{'tb'，'tbs'，'tb'，'tb'}
b=b/1024^4；
大小写{pb'，pbs'，pb'，pb}
b=b/1024^5；
否则
returnType='bytes'；
结束
如果nargin 2&&~为空（fid）&&fid>2
尝试
fprintf（fid，[num2str（b）'returnType'\n']）；
抓住
警告（['fid（'num2str（fid）'）无法编辑。因此，输出将写入屏幕上。'）；
fprintf（1，[num2str（b）'returnType'\n']）；
结束
结束
结束