switch language models in sphinx

void switchModel(ps_decoder_t* ps, const char* modelFileName, const char* modelName)
{
        cmd_ln_t *config = ps_get_config(ps);
        logmath_t *logmath = ps_get_logmath(ps);
        ngram_model_t *baseLanguageModel = ps_get_lmset(ps);
        ngram_model_t *newLanguageModelToAdd = ngram_model_read(config, modelFileName, NGRAM_AUTO, logmath);

        ngram_model_set_add(baseLanguageModel, newLanguageModelToAdd, modelName, 1.0, TRUE);
        ngram_model_set_select(baseLanguageModel, modelName);
}