gidx_union_volume()

static float gidx_union_volume ( GIDX *  a, GIDX *  b  )

static

Definition at line 261 of file gserialized_gist_nd.c.

References gidx_dimensionality_check(), gidx_is_unknown(), and gidx_volume().

Referenced by gserialized_gist_penalty().

{
        float result;
        int i;
        int ndims_a, ndims_b;

        POSTGIS_DEBUG(5,"entered function");

        if ( a == NULL && b == NULL )
        {
                elog(ERROR, "gidx_union_volume received two null arguments");
                return 0.0;
        }

        if ( a == NULL || gidx_is_unknown(a) )
                return gidx_volume(b);

        if ( b == NULL || gidx_is_unknown(b) )
                return gidx_volume(a);

        if ( gidx_is_unknown(a) && gidx_is_unknown(b) )
        {
                return 0.0;
        }

        /* Ensure 'a' has the most dimensions. */
        gidx_dimensionality_check(&a, &b);

        ndims_a = GIDX_NDIMS(a);
        ndims_b = GIDX_NDIMS(b);

        /* Initialize with maximal length of first dimension. */
        result = Max(GIDX_GET_MAX(a,0),GIDX_GET_MAX(b,0)) - Min(GIDX_GET_MIN(a,0),GIDX_GET_MIN(b,0));

        /* Multiply by maximal length of remaining dimensions. */
        for ( i = 1; i < ndims_b; i++ )
        {
                result *= (Max(GIDX_GET_MAX(a,i),GIDX_GET_MAX(b,i)) - Min(GIDX_GET_MIN(a,i),GIDX_GET_MIN(b,i)));
        }

        /* Add in dimensions of higher dimensional box. */
        for ( i = ndims_b; i < ndims_a; i++ )
        {
                result *= (GIDX_GET_MAX(a,i) - GIDX_GET_MIN(a,i));
        }

        POSTGIS_DEBUGF(5, "volume( %s union %s ) = %.12g", gidx_to_string(a), gidx_to_string(b), result);

        return result;
}

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