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From |
George Vega Yon <g.vegayon@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: MATA function modifies global variables |

Date |
Fri, 7 Jun 2013 09:30:02 -0400 |

Now I get why the performance other functions didn't change after I replace several variables by pointers... Great news though! A must know for MATA users. Thanks! George Vega Yon 7 647 2552 http://cl.linkedin.com/in/georgevegayon 2013/6/6 Sergiy Radyakin <serjradyakin@gmail.com>: > That's right. See the chapter "The by-address calling convention" in > the mata manual and a quote: > > "Arguments are passed to functions by address, not by value. If you > change the value of an argument, > you will change the caller’s argument." > > Here are some simpler examples: > mata mata clear > mata > Y=1,2,3,4,5 > real matrix foobar(real matrix y) { > y=y' > return(y) > } > > Y > foobar(Y) > foobar(Y) > > > S="abcdefg" > strlen(S) > string foobars(string s) { > s=substr(s,1,strlen(s)-1) > return(s) > } > > S > foobars(S) > foobars(S) > > > N=17 > real foobarn(real n) { > n=n-1 > return(n) > } > > foobarn(N) > foobarn(N) > > > end > > > > Best, Sergiy > > On Thu, Jun 6, 2013 at 4:23 PM, George Vega Yon <g.vegayon@gmail.com> wrote: >> Sorry, I forgot to change that, blop_vec() is "myfun" and neig is "X". >> I'll just rewrite the code with the corrections. Thank you! >> >> __________________________ >> mata: >> /* Function definition */ >> real colvector myfun(real colvector y, real matrix x) { >> >> real matrix z >> >> y = y' >> x = x' >> >> ... some code lines (no poiter to Y or X)... >> >> return(z) >> } >> >> X = ( >> 0,0 \ >> 1,0 \ >> 1,1 \ >> 0,1 \ >> 1/2,1/2\ >> .9,1/2 \ >> .2,.5 \ >> .8,.3 >> ) >> Y = runiform(rows(X),1) >> >> >> /* Testing */ >> timer_clear() >> for(i=1;i<=100;i++) { >> timer_on(1) >> YC = myfun(Y,X) >> timer_off(1) >> } >> timer() >> >> end >> __________________________ >> George Vega Yon >> 7 647 2552 >> http://cl.linkedin.com/in/georgevegayon >> >> >> 2013/6/6 Sergiy Radyakin <serjradyakin@gmail.com>: >>> Can you tell us what neig is? what blop_vec is? >>> >>> On Thu, Jun 6, 2013 at 4:10 PM, George Vega Yon <g.vegayon@gmail.com> wrote: >>>> Dear Statalisters, >>>> >>>> I'm having a weird problem on variables' scope. I have a function that >>>> takes two objects (a real colvector and a matrix) wich, once inside >>>> the function, are transposed. This function returns a matrix (builded >>>> inside of the function of course). The problem is that the function >>>> seems to actually transpose the global objects (not only the copies >>>> within the function), thing that, as far as I know, should not be >>>> happening as I'm not using pointers to the global objects. >>>> >>>> My code looks something like this >>>> __________________________ >>>> mata: >>>> /* Function definition */ >>>> real colvector myfun(real colvector y, real matrix x) { >>>> >>>> real matrix z >>>> >>>> y = y' >>>> x = x' >>>> >>>> ... some code lines (no poiter to Y or X)... >>>> >>>> return(z) >>>> } >>>> >>>> Y = runiform(rows(neig),1) >>>> X = ( >>>> 0,0 \ >>>> 1,0 \ >>>> 1,1 \ >>>> 0,1 \ >>>> 1/2,1/2\ >>>> .9,1/2 \ >>>> .2,.5 \ >>>> .8,.3 >>>> ) >>>> >>>> >>>> /* Testing */ >>>> timer_clear() >>>> for(i=1;i<=100;i++) { >>>> timer_on(1) >>>> YC = blop_vec(Y,X) >>>> timer_off(1) >>>> } >>>> timer() >>>> >>>> end >>>> __________________________ >>>> >>>> >>>> I get the error >>>> >>>> __________________________ >>>> myfun: 3203 Y[1,8] found where colvector required >>>> <istmt>: - function returned error >>>> __________________________ >>>> >>>> Thanks in advanced, >>>> >>>> George Vega Yon >>>> 7 647 2552 >>>> http://cl.linkedin.com/in/georgevegayon >>>> * >>>> * For searches and help try: >>>> * http://www.stata.com/help.cgi?search >>>> * http://www.stata.com/support/faqs/resources/statalist-faq/ >>>> * http://www.ats.ucla.edu/stat/stata/ >>> * >>> * For searches and help try: >>> * http://www.stata.com/help.cgi?search >>> * http://www.stata.com/support/faqs/resources/statalist-faq/ >>> * http://www.ats.ucla.edu/stat/stata/ >> * >> * For searches and help try: >> * http://www.stata.com/help.cgi?search >> * http://www.stata.com/support/faqs/resources/statalist-faq/ >> * http://www.ats.ucla.edu/stat/stata/ > > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/faqs/resources/statalist-faq/ > * http://www.ats.ucla.edu/stat/stata/ * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/

**References**:**st: MATA function modifies global variables***From:*George Vega Yon <g.vegayon@gmail.com>

**Re: st: MATA function modifies global variables***From:*Sergiy Radyakin <serjradyakin@gmail.com>

**Re: st: MATA function modifies global variables***From:*George Vega Yon <g.vegayon@gmail.com>

**Re: st: MATA function modifies global variables***From:*Sergiy Radyakin <serjradyakin@gmail.com>

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