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           CPU_XOR_S, CPU_EQUAL_S - macros for manipulating CPU sets


           #define _GNU_SOURCE             /* See feature_test_macros(7) */
           #include <sched.h>
           void CPU_ZERO(cpu_set_t *set);
           void CPU_SET(int cpu, cpu_set_t *set);
           void CPU_CLR(int cpu, cpu_set_t *set);
           int  CPU_ISSET(int cpu, cpu_set_t *set);
           int  CPU_COUNT(cpu_set_t *set);
           void CPU_AND(cpu_set_t *destset,
                        cpu_set_t *srcset1, cpu_set_t *srcset2);
           void CPU_OR(cpu_set_t *destset,
                        cpu_set_t *srcset1, cpu_set_t *srcset2);
           void CPU_XOR(cpu_set_t *destset,
                        cpu_set_t *srcset1, cpu_set_t *srcset2);
           int  CPU_EQUAL(cpu_set_t *set1, cpu_set_t *set2);
           cpu_set_t *CPU_ALLOC(int num_cpus);
           void CPU_FREE(cpu_set_t *set);
           size_t CPU_ALLOC_SIZE(int num_cpus);
           void CPU_ZERO_S(size_t setsize, cpu_set_t *set);
           void CPU_SET_S(int cpu, size_t setsize, cpu_set_t *set);
           void CPU_CLR_S(int cpu, size_t setsize, cpu_set_t *set);
           int  CPU_ISSET_S(int cpu, size_t setsize, cpu_set_t *set);
           int  CPU_COUNT_S(size_t setsize, cpu_set_t *set);
           void CPU_AND_S(size_t setsize, cpu_set_t *destset,
                        cpu_set_t *srcset1, cpu_set_t *srcset2);
           void CPU_OR_S(size_t setsize, cpu_set_t *destset,
                        cpu_set_t *srcset1, cpu_set_t *srcset2);
           void CPU_XOR_S(size_t setsize, cpu_set_t *destset,
                        cpu_set_t *srcset1, cpu_set_t *srcset2);
           int  CPU_EQUAL_S(size_t setsize, cpu_set_t *set1, cpu_set_t *set2);


           The cpu_set_t data structure represents a set of CPUs.   CPU  sets  are
           used by sched_setaffinity(2) and similar interfaces.
           The  cpu_set_t data type is implemented as a bitset.  However, the data
           structure treated as considered opaque: all manipulation  of  CPU  sets
           should be done via the macros described in this page.
           since the above macros may evaluate the argument more than once.
           The first available CPU on the system corresponds to a cpu value of  0,
           the  next CPU corresponds to a cpu value of 1, and so on.  The constant
           CPU_SETSIZE (currently 1024) specifies a value  one  greater  than  the
           maximum CPU number that can be stored in cpu_set_t.
           The following macros perform logical operations on CPU sets:
           CPU_AND()        Store the intersection of the sets srcset1 and srcset2
                            in destset (which may be one of the source sets).
           CPU_OR()         Store the union of the sets  srcset1  and  srcset2  in
                            destset (which may be one of the source sets).
           CPU_XOR()        Store the XOR of the sets srcset1 and srcset2 in dest-
                            set (which may be one of the source  sets).   The  XOR
                            means  the  set  of CPUs that are in either srcset1 or
                            srcset2, but not both.
           CPU_EQUAL()      Test whether two CPU  set  contain  exactly  the  same
       Dynamically sized CPU sets
           Because  some  applications may require the ability to dynamically size
           CPU sets (e.g., to allocate sets larger than that defined by the  stan-
           dard  cpu_set_t  data type), glibc nowadays provides a set of macros to
           support this.
           The following macros are used to allocate and deallocate CPU sets:
           CPU_ALLOC()      Allocate a CPU set large enough to hold  CPUs  in  the
                            range 0 to num_cpus-1.
           CPU_ALLOC_SIZE() Return  the size in bytes of the CPU set that would be
                            needed to hold CPUs in  the  range  0  to  num_cpus-1.
                            This macro provides the value that can be used for the
                            setsize argument in  the  CPU_*_S()  macros  described
           CPU_FREE()       Free a CPU set previously allocated by CPU_ALLOC().
           The  macros  whose names end with "_S" are the analogs of the similarly
           named macros without the suffix.  These macros perform the  same  tasks
           as  their  analogs, but operate on the dynamically allocated CPU set(s)
           whose size is setsize bytes.


           CPU_ISSET() and CPU_ISSET_S() return nonzero if cpu is in  set;  other-
           wise, it returns 0.
           CPU_COUNT() and CPU_COUNT_S() return the number of CPUs in set.
           in glibc 2.3.3.
           CPU_COUNT() first appeared in glibc 2.6.
           CPU_AND(),     CPU_OR(),     CPU_XOR(),    CPU_EQUAL(),    CPU_ALLOC(),
           CPU_ALLOC_SIZE(), CPU_FREE(), CPU_ZERO_S(),  CPU_SET_S(),  CPU_CLR_S(),
           CPU_ISSET_S(),  CPU_AND_S(), CPU_OR_S(), CPU_XOR_S(), and CPU_EQUAL_S()
           first appeared in glibc 2.7.


           These interfaces are Linux-specific.


           To duplicate a CPU set, use memcpy(3).
           Since CPU sets are bitsets allocated in units of long words, the actual
           number of CPUs in a dynamically allocated CPU set will be rounded up to
           the next multiple of sizeof(unsigned long).  An application should con-
           sider the contents of these extra bits to be undefined.
           Notwithstanding  the  similarity  in  the names, note that the constant
           CPU_SETSIZE indicates the number of CPUs in  the  cpu_set_t  data  type
           (thus, it is effectively a count of bits in the bitset), while the set-
           size argument of the CPU_*_S() macros is a size in bytes.
           The data types for arguments and return values shown  in  the  SYNOPSIS
           are  hints  what  about is expected in each case.  However, since these
           interfaces are implemented as macros, the  compiler  won't  necessarily
           catch all type errors if you violate the suggestions.


           On  32-bit  platforms with glibc 2.8 and earlier, CPU_ALLOC() allocates
           twice as much space as is  required,  and  CPU_ALLOC_SIZE()  returns  a
           value  twice  as  large  as  it should.  This bug should not affect the
           semantics of a program, but does result in wasted memory and less effi-
           cient operation of the macros that operate on dynamically allocated CPU
           sets.  These bugs are fixed in glibc 2.9.


           The following program demonstrates the use of some of the  macros  used
           for dynamically allocated CPU sets.
           #define _GNU_SOURCE
           #include <sched.h>
           #include <stdlib.h>
           #include <unistd.h>
           #include <stdio.h>
           #include <assert.h>
           main(int argc, char *argv[])
               size = CPU_ALLOC_SIZE(num_cpus);
               CPU_ZERO_S(size, cpusetp);
               for (cpu = 0; cpu < num_cpus; cpu += 2)
                   CPU_SET_S(cpu, size, cpusetp);
               printf("CPU_COUNT() of set:    %d\n", CPU_COUNT_S(size, cpusetp));


           sched_setaffinity(2), pthread_attr_setaffinity_np(3), pthread_setaffin-
           ity_np(3), cpuset(7)

    Linux 2012-03-15 CPU_SET(3)


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