Using Coarrays to Parallelize Legacy Fortran Applications: Strategy and Case Study

Table 2

Runtime in seconds for parallel using 128 bands, and different collective sum routines.

	Number of Images
	1	2	4	8	16	32
Intel Serial co_sum	35.55	19.80	11.69	9.73	18.71	66.82
Intel Parallel co_sum	37.30	19.33	10.00	6.17	4.62	5.41
Cray Native co_sum	46.71	23.68	11.88	6.06	3.06	1.73