Read a portion from a persistent globally shared memory
[sim, data] = ld_read_global_memory(sim, events, index, ident_str, datatype, ElementsToRead)
data *+(ElementsToRead) - data
index * - index to store the data. Starts at 1
ident_str (string) - name of the memory
datatype - ORTD datatype of the memory (for now only ORTD.DATATYPE_FLOAT)
ElementsToRead (integer) - number of elements to read from the memory