In ROMIO, setting hints looks like this:<\/p>\n
MPI_Info info;
\nMPI_Info_create(&info);
\nMPI_Info_set(“cb_buffer_size”, “8388608”);<\/p><\/blockquote>\nSetting these hints in the program\u00a0 can make sense in many cases — for example, you know something specific about the workload and wish to guide ROMIO’s optimizations a bit.\u00a0 But what if you want to explore the impact of hints on your program?\u00a0 There are a few options to do so:<\/p>\n
\n
- \u00a0Modify your program to look at an environment variable and use that as the value for your hint.<\/li>\n
- \u00a0Take a command line parameter.<\/li>\n
- Repeatedly edit and re-compile your program.<\/li>\n<\/ul>\n
While good practice, the approaches require additional work.\u00a0 It also assumes access to the source code — common, but not a guarantee.
\nAdditionally, we notice very few users set hints on their own.\u00a0 They will gladly do so if we suggest it, but what would be great is if every application on a system ran with the best hints for that system.\u00a0\u00a0 Sometimes you can count on the system’s vendor to set the defaults, but it is our experience that vendor defaults are exceedingly conservative.
\nWe added a new feature in ROMIO called “system hints<\/a>“.\u00a0\u00a0 You can now populate a config file with the same key-value pairs you would pass to MPI_Info_set and ROMIO will add those hints to your program.
\nHere’s an example of what that file might look like:<\/p>\n$ cat romio_hints
\nromio_cb_read enable
\nromio_cb_write enable
\ncb_config_list *:2<\/p><\/blockquote>\nBy default, ROMIO will look for \/etc\/romio-hints<\/tt> , but you can set the environment variable ROMIO_HINTS to select a different location (for example, your application’s working directory)<\/p>\n","protected":false},"excerpt":{"rendered":"
In ROMIO, setting hints looks like this: MPI_Info info; MPI_Info_create(&info); MPI_Info_set(“cb_buffer_size”, “8388608”); Setting these hints in the program\u00a0 can make sense in many cases — for example, you know something specific about the workload and wish to guide ROMIO’s optimizations a bit.\u00a0 But what if you want to explore the impact of hints on your …<\/p>\n","protected":false},"author":362,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"categories":[1],"tags":[],"class_list":["post-31","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"acf":[],"_links":{"self":[{"href":"https:\/\/wordpress.cels.anl.gov\/romio\/wp-json\/wp\/v2\/posts\/31","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/wordpress.cels.anl.gov\/romio\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/wordpress.cels.anl.gov\/romio\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/wordpress.cels.anl.gov\/romio\/wp-json\/wp\/v2\/users\/362"}],"replies":[{"embeddable":true,"href":"https:\/\/wordpress.cels.anl.gov\/romio\/wp-json\/wp\/v2\/comments?post=31"}],"version-history":[{"count":1,"href":"https:\/\/wordpress.cels.anl.gov\/romio\/wp-json\/wp\/v2\/posts\/31\/revisions"}],"predecessor-version":[{"id":570,"href":"https:\/\/wordpress.cels.anl.gov\/romio\/wp-json\/wp\/v2\/posts\/31\/revisions\/570"}],"wp:attachment":[{"href":"https:\/\/wordpress.cels.anl.gov\/romio\/wp-json\/wp\/v2\/media?parent=31"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wordpress.cels.anl.gov\/romio\/wp-json\/wp\/v2\/categories?post=31"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wordpress.cels.anl.gov\/romio\/wp-json\/wp\/v2\/tags?post=31"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}