Μake error

[Konagra]

i have made this Makefile but i see this error :

ERROR:
Makefile:3: /config.mk: No such file or directory
make: *** No rule to make target '/config.mk'. Stop.

Makefile
ROOT_DIR :$(realpath ../../..)
include $(ROOT_DIR)/config.mk

PROJECT := outerproduct

SRC_DIR := $(VORTEX_HOME)/tests/opencl/$(PROJECT)

SRCS := $(SRC_DIR)/main.cc $(SRC_DIR)/oclUtils.cpp $(SRC_DIR)/shrUtils.cpp $(SRC_DIR)/cmd_arg_reader.cpp

kernel.cl: $(SRC_DIR)/kernel.cl
cp $< $@

KERNEL_SRCS := kernel.cl

OPTS ?= -size=64

include ../common.mk

WHAT SHOULD I DO TO FIX IT ? IT DOES NOT ALSO ALLOW ME TO RUN THIS INSTRACTION :
make -C /vortex/runtime
make: Entering directory '/vortex/runtime'
Makefile:2: /vortex/config.mk: No such file or directory
make: *** No rule to make target '/vortex/config.mk'. Stop.
make: Leaving directory '/vortex/runtime'