     unsigned last_example = min(total_num_examples, example_num_base + examples_per_block);
 
     unsigned example_num = example_num_base;
-#if 0
+#if 1
     for (;  example_num < last_example - 3;  example_num += 4) {
         const float * input1 = feature_vectors + example_num * feature_vector_width;
         const float * input2 = input1 + feature_vector_width;

    }
#endif

#if 1
    for (;  example_num < last_example;  example_num += 1) {
        const float * input1 = feature_vectors + example_num * feature_vector_width;
        const float * input2 = input1 + feature_vector_width;


        next_layer_outputs = this_layer_outputs + no;

#if defined(__DEVICE_EMULATION__) && 0
        if (tid == 0)
            fprintf(stderr, "fprop: tid %d layer %d ni %d no %d last_layer_outputs %p this_layer_outputs %p next_layer_outputs %p\n",
                    tid, l, ni, no, last_layer_outputs, this_layer_outputs,
