To: J3 07-315 From: Bill Long and John Reid Subject: UTI 119 (p547): Annex B note on collectives Date: 2007 October 26 References: J3/07-007r3 Discussion Making the collectives elemental would be a technical change with these effects: 1. There would have to be a restriction that TEAM be scalar. 2. Either there would have to be a restriction that the first argument be an array when the second argument is an array or the functionality of broadcasting to an array argument would need to be added. 3. It would exclude a future extension for a complete reduction to be performed when the input argument is an array and the output argument is a scalar. We are therefore not proposing this change. It is the elemental nature of the collectives that forces the CO_MAXLOC and CO_MINLOC to return image indices rather than an array of subscripts. Yes, we could add a CO_DIM argument, but a call with such an argument would involve a number of independent sub-teams and more synchronization than necessary. The effect is available by declaring another IMAGE_TEAM variable for the sub-team on each image. Futhermore, adding a CO_DIM argument represents an increase in the size of the co-array feature at a time when there is some sentiment within WG5 that the co-array feature should be reduced. Edits to 07-007r3: none