A quick benchmark to evaluate the cost of converting a MPI collective communication name into the collective identifier. The benchmark does not check the cost for a particular permutation of the collectives, as they all have the same chance to be in the configuration file I look at the cost to search for all of them once.

check_coll_names.c

#include <stdio.h>
#include <string.h>
#include <time.h>
#include <inttypes.h>

extern int mca_coll_base_name_to_colltype(const char* name);

typedef enum COLLTYPE {
    ALLGATHER = 0,       /*  0 */
    ALLGATHERV,          /*  1 */
    ALLREDUCE,           /*  2 */
    ALLTOALL,            /*  3 */
    ALLTOALLV,           /*  4 */
    ALLTOALLW,           /*  5 */
    BARRIER,             /*  6 */
    BCAST,               /*  7 */
    EXSCAN,              /*  8 */
    GATHER,              /*  9 */
    GATHERV,             /* 10 */
    REDUCE,              /* 11 */
    REDUCESCATTER,       /* 12 */
    REDUCESCATTERBLOCK,  /* 13 */
    SCAN,                /* 14 */
    SCATTER,             /* 15 */
    SCATTERV,            /* 16 */
    NEIGHBOR_ALLGATHER,  /* 17 */
    NEIGHBOR_ALLGATHERV, /* 18 */
    NEIGHBOR_ALLTOALL,   /* 19 */
    NEIGHBOR_ALLTOALLV,  /* 20 */
    NEIGHBOR_ALLTOALLW,  /* 21 */
    COLLCOUNT            /* 22 end counter keep it as last element */
} COLLTYPE_T;

static const char* colltype_translation_table[] = {
    [ALLGATHER] = "allgather",
    [ALLGATHERV] = "allgatherv",
    [ALLREDUCE] = "allreduce",
    [ALLTOALL] = "alltoall",
    [ALLTOALLV] = "alltoallv",
    [ALLTOALLW] = "alltoallw",
    [BARRIER] = "barrier",
    [BCAST] = "bcast",
    [EXSCAN] = "exscan",
    [GATHER] = "gather",
    [GATHERV] = "gatherv",
    [REDUCE] = "reduce",
    [REDUCESCATTER] = "reduce_scatter",
    [REDUCESCATTERBLOCK] = "reduce_scatter_block",
    [SCAN] = "scan",
    [SCATTER] = "scatter",
    [SCATTERV] = "scatterv",
    [NEIGHBOR_ALLGATHER] = "neighbor_allgather",
    [NEIGHBOR_ALLGATHERV] = "neighbor_allgatherv",
    [NEIGHBOR_ALLTOALL] = "neighbor_alltoall",
    [NEIGHBOR_ALLTOALLV] = "neighbor_alltoallv",
    [NEIGHBOR_ALLTOALLW] = "neighbor_alltoallw",
    [COLLCOUNT] = NULL
};

int mca_coll_base_name_to_colltype_gb(const char* name)
{
    if( 'n' == name[0] ) {
        if( 0 == strncmp(name, "neighbor_all", 12) ) {
            if( 't' != name[12] ) {
                if( 0 == strncmp(name+12, "gather", 6) ) {
                    if('\0' == name[18]) return NEIGHBOR_ALLGATHER;
                    if( 'v' == name[18]) return NEIGHBOR_ALLGATHERV;
                }
            } else {
                if( 0 == strncmp(name+12, "toall", 5) ) {
                    if( '\0' == name[17] ) return NEIGHBOR_ALLTOALL;
                    if( 'v' == name[17] ) return NEIGHBOR_ALLTOALLV;
                    if( 'w' == name[17] ) return NEIGHBOR_ALLTOALLW;
                }
            }
        }
        return -1;
    }
    if( 'a' == name[0] ) {
        if( 0 != strncmp(name, "all", 3) ) {
            return -1;
        }
        if( 't' != name[3] ) {
            if( 'r' == name[3] ) {
                if( 0 == strcmp(name+3, "reduce") )
                    return ALLREDUCE;
            } else {
                if( 0 == strncmp(name+3, "gather", 6) ) {
                    if( '\0' == name[9] ) return ALLGATHER;
                    if( 'v'  == name[9] ) return ALLGATHERV;
                }
            }
        } else {
            if( 0 == strncmp(name+3, "toall", 5) ) {
                if( '\0' == name[8] ) return ALLTOALL;
                if( 'v' == name[8] ) return ALLTOALLV;
                if( 'w' == name[8] ) return ALLTOALLW;
            }
        }
        return -1;
    }
    if( 'r' > name[0] ) {
        if( 'b' == name[0] ) {
            if( 0 == strcmp(name, "barrier") )
                return BARRIER;
            if( 0 == strcmp(name, "bcast") )
                return BCAST;
        } else if( 'g'== name[0] ) {
            if( 0 == strncmp(name, "gather", 6) ) {
                if( '\0' == name[6] ) return GATHER;
                if( 'v' == name[6] ) return GATHERV;
            }
        }
        if( 0 == strcmp(name, "exscan") )
            return EXSCAN;
        return -1;
    }
    if( 's' > name[0] ) {
        if( 0 == strncmp(name, "reduce", 6) ) {
            if( '\0' == name[6] ) return REDUCE;
            if( '_' == name[6] ) {
                if( 0 == strncmp(name+7, "scatter", 7) ) {
                    if( '\0' == name[14] ) return REDUCESCATTER;
                    if( 0 == strcmp(name+14, "_block") ) return REDUCESCATTERBLOCK;
                }
            }
        }
        return -1;
    }
    if( 0 == strcmp(name, "scan") )
        return SCAN;
    if( 0 == strcmp(name, "scatterv") )
        return SCATTERV;
    if( 0 == strcmp(name, "scatter") )
        return SCATTER;
    return -1;
}

int mca_coll_base_name_to_colltype_ch(const char* name)
{
    int i;
    for (i = 0; i < COLLCOUNT; i++) {
        if (0 == strcmp(name, colltype_translation_table[i])) {
            return i;}
    }
    return -1;
}

uint64_t diff(struct timespec* start, struct timespec* end)
{
    uint64_t temp = (end->tv_sec - start->tv_sec) * 1000000000;
    temp += end->tv_nsec - start->tv_nsec;
    return temp;
}

#define MAX_REPEAT 1000

int main(int argc, char* argv[])
{
    int rc, i;
    struct timespec start, end;

    clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &start);
    for(int repeat = 0; repeat < 1000; repeat++ ) {
        for( i = 0; NULL != colltype_translation_table[i]; i++ ) {
            rc = mca_coll_base_name_to_colltype_gb(colltype_translation_table[i]);
            if( rc != i ) {
                printf("This is bad for index %d collective %s\n", i, colltype_translation_table[i]);
            }
        }
    }
    clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &end);
    printf("gb: search all collectives for %ld secs\n", diff(&start, &end)/MAX_REPEAT);

    clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &start);
    for(int repeat = 0; repeat < 1000; repeat++ ) {
        for( i = 0; NULL != colltype_translation_table[i]; i++ ) {
            rc = mca_coll_base_name_to_colltype_ch(colltype_translation_table[i]);
            if( rc != i ) {
                printf("This is bad for index %d collective %s\n", i, colltype_translation_table[i]);
            }
        }
    }
    clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &end);
    printf("ch: search all collectives for %ld secs\n", diff(&start, &end)/MAX_REPEAT);

    return 0;
}