RFC: extracting coefficients of a multivariate polynomial
Subject: RFC: extracting coefficients of a multivariate polynomial
From: Stavros Macrakis
Date: Fri, 25 Apr 2008 11:02:54 -0400
On Fri, Apr 25, 2008 at 10:40 AM, Richard Fateman <fateman at cs.berkeley.edu>
wrote:
> hmm, I didn't get the same timing results, maybe because I set
> ratvars:[x,y,z] first ....
>
> %o40) [x, y, z]
> (%i41) ex:rat((x+y+z)^200)$
> Evaluation took 00.90 seconds (00.90 elapsed)
> (%i42) thru 10 do ratcoef(ex,x,100)$
> Evaluation took 7.34 seconds (7.34 elapsed)
> (%i43) thru 10 do ratcoef(ex,z,100)$
> Evaluation took 00.90 seconds (00.90 elapsed)
>
This seems to imply that ratcoef first converts to the current ratvars
before selecting the coeff.
That doesn't seem right.
-s