Re: implementation of boschloo's test: very slow execution

["Michael Blasnik" <michael.blasnik@verizon.net>]

...

I have a couple of potential speed imrpovement ideas (besides moving it to 
Mata):

1) Do you really need to get the p value to 4 decimals?  If you changed

qui gen double p = (_n-1)/10001 to qui gen double p = (_n-1)/1001

Then you have a 90% reduction in some of the calculations.

2) I don't know much about this test, but wouldn't the optimum point be a smooth 
function of p?  If that is so, you may want to create an iterative approach to 
narrowing the range of p.  Start with perhaps p ranging by  .01.  Then just keep 
the interval on either side of the optimum and reduce the increment to .001. 
That may reduce the calculations substantially.

3) Don't use tabi.  -tabi- requires a preserve and has a lot of ado machinery to 
set up the desired table.   It ends up creating a dataset with RxC observations 
and a frequency weight variable that contains the counts.   You could instead 
hardwire a 2x2 table with values for row, col, and fw.  A loop would then just 
change the fw values to cycle through all of the n1 and n2 values.  You could 
then  use -post- to post the values of p_exact, xx1 and xx2.  You may then be 
able to do the binomial calculation and summation just once on the resulting 
dastaset.

I'm not sure I understand the algorithm fully enough to be sure how these 
changes would work or could be optimized and combined, but I wouldn't be 
suprised with a large speed improvement.

Michael Blasnik



*
*   For searches and help try:
*   http://www.stata.com/support/faqs/res/findit.html
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/