The OMP_AFFINITY_FORMAT environment variable sets the initial value of the affinity-format-var ICV which defines the format when displaying OpenMP thread affinity information.
The value of this environment variable is a character string that may contain as substrings one or more field
specifiers, in addition to other characters. The format of each field specifier is
%[[[0].] size ] type
where an individual field specifier must contain the percent symbol (%) and a type. The type can be a single character short name or its corresponding long name delimited with curly braces, such as %n or %{thread_num}. A literal percent is specified as %%. Field specifiers can be provided in any order.
The 0 modifier indicates whether or not to add leading zeros to the output, following any indication of sign or base. The . modifier indicates the output should be right justified when size is specified. By default, output is left justified. The minimum field length is size, which is a decimal digit string with a non-zero first digit. If no size is specified, the actual length needed to print the field will be used. If the 0 modifier is used with type of A, {thread_affinity}, H, {host}, or a type that is not printed as a number, the result is unspecified. Any other characters in the format string that are not part of a field specifier will be included literally in the output.
| Table 6.2: | Available Field Types for Formatting OpenMP Thread Affinity Information |
| Short Name | Long Name | Meaning |
| t | team_num | The value returned by omp_get_team_num(). |
| T | num_teams | The value returned by omp_get_num_teams(). |
| L | nesting_level | The value returned by omp_get_level(). |
| n | thread_num | The value returned by omp_get_thread_num(). |
| N | num_threads | The value returned by omp_get_num_threads(). |
| a | ancestor_tnum | The value returned by omp_get_ancestor_thread_num(level), where level is omp_get_level() minus 1. |
| H | host | The name for the host machine on which the OpenMP program is running. |
| P | process_id | The process identifier used by the implementation. |
| i | native_thread_id | The native thread identifier used by the implementation. |
| A | thread_affinity | The list of numerical identifiers, in the format of a comma-separated list of integers or integer ranges, that represent processors on which a thread may execute, subject to OpenMP thread affinity control and/or other external affinity mechanisms. |
Implementations may define additional field types. If an implementation does not have information for a field type, "undefined" is printed for this field when displaying the OpenMP thread affinity information.
setenv OMP_AFFINITY_FORMAT
"Thread Affinity: %0.3L %.8n %.15{thread_affinity} %.12H"
The above example causes an OpenMP implementation to display OpenMP thread affinity information in
the following form:
Thread Affinity: 001 0 0-1,16-17 nid003
Thread Affinity: 001 1 2-3,18-19 nid003