m1_limits.hlp

是一个经济学管理应用软件 很难找的 但是经济学学生又必须用到

{smcl}
{* 03may2005}{...}
{cmd:help m1 limits}
{hline}
{* index limits}{...}
{* index memory utilization}{...}
{* index matsize tt}{...}
{* index maximum length of string}{...}
{* index maximum size of matrix}{...}

{title:Title}

{pstd}
{bf:[M-1] limits -- Limits and memory utilization}


{title:Summary}

    Limits:
	                              minimum          maximum
	{hline 54}
	Scalars, vectors, matrices
	    rows                         0       2,147,483,647
	    columns                      0       2,147,483,647

        String elements, length          0       2,147,483,647
	{hline 54}
	Stata's {cmd:matsize} plays no role in these limits


    Size approximations:
				      memory requirements
	{hline 66}
	real matrices                 {it:oh} + {it:r}*{it:c}*8 
        complex matrices              {it:oh} + {it:r}*{it:c}*16 
        pointer matrices              {it:oh} + {it:r}*{it:c}*8
	string matrices               {it:oh} + {it:r}*{it:c}*8 + {it:total_length_of_strings}
	{hline 66}
	where {it:r} and {it:c} represent the number of rows and columns and where
	{it:oh} is overhead and is approximately 64 bytes
       

{title:Description}

{pstd}
Mata imposes limits, but those limits are of little importance 
compared with the memory requirements.  Mata stores matrices in memory and 
requests the memory for them from the operating system.


{title:Remarks}

{pstd}
Mata requests (and returns) memory from the operating system as it needs it,
and if the operating system cannot provide it, Mata issues the error:

	: {cmd:x = foo(A, B)}
	             {err}foo():  3900  unable to allocate{txt} ...
		   {err}<istmt>:     -  function returned error{txt}
	r(3900);

{pstd}
	
{pstd}
Stata's {cmd:matsize} (see {bf:{help matsize:[R] matsize}}) 
and 
Stata's {cmd:set memory} value (see {bf:{help memory:[D] memory}}) 
play no role in Mata or, at least, they play no direct role.  
{cmd:set} {cmd:memory} specifies 
the amount of memory to be set aside for the storage of Stata's dataset;
hence, larger values of {cmd:set} {cmd:memory} leave less memory 
for Mata.


{title:Also see}

{psee}
Manual:  {bf:[M-1] limits}

{psee}
Online:  
{bf:{help mata_memory:[M-3] mata memory}};
{bf:{help mf_mindouble:[M-5] mindouble()}};
{bf:{help m1_intro:[M-1] intro}}
{p_end}