On Sat, 8 Aug 2009, Allin Cottrell wrote: > On Sat, 8 Aug 2009, Sven Schreiber quoted: > > > That is, you can use the keyword "rfunc" to indicate that you're > > > giving a constraint function rather than explicit statement of a > > > restriction. As in Jack's script, this function should take as > > > its single argument the coefficient vector (in "pointer" form), > > > and it should return a vector that is zero under H0, non-zero > > > under the alternative...
and replied: > > > > Certainly a very nice feature! > > > > Why is the pointer form necessary? And I reponded: > Ah, it's not actually necessary, though it is a bit more > efficient. However, we do need to standardize on pointer-form or > not. I suppose the straight, non-pointer form is more "natural". Fixed in CVS. The signature for the callback function for a nonlinear restriction, in the context of the "restrict" command, should now be: function foo (const matrix m) (replace "foo" and "m" as desired). This is linked to a general modification of the effect of the "const" qualifier for matrix arguments: if you promise not to modify a matrix argument then you get the matrix "directly", not a copy. That is, it's the same, speed-wise, as passing a "pointer to matrix" (but it's an error if you try to modify the argument). I think the business of using the pointer formulation purely for speed-up in gretl was potentially a bit confusing; it's no longer necessary for matrices, just use "const" instead. Allin
