Error: cts.tcl, 146 ERROR: Reading sources failed.(When performing cluster flops)

[tfcdys]

When I use the design execution flow under asap7, I report an error when adding cluster flops to other designs after imitating aes-mbff. Multiple designs appear：
Error: cts.tcl, 146 ERROR: Reading sources failed.
As shown in the figure: For example, for design: uart, I modify the given config.mk and only add ：
export CLUSTER_FLOPS = 1.
Then the execution reports an error.
(Please note that it can be executed correctly when no modifications are made).

[maliberty]

This makes little sense as cluster_flops is part of global_place.tcl not cts.tcl. Can you provide a test case?

[tfcdys]

Yes, this is indeed part of global_place.tcl, but after I add the variable "CLUSTER_FLOPS " to case: uart and jpeg in asap7, the above error appears at cts.tcl. My specific steps are as follows:
Step1: I copy an asap7 uart folder as uart-mbff, and modify the config.mk file to add the variable "CLUSTER_FLOPS " as follows：

export PLATFORM               = asap7
export CORNER                 = TC

export DESIGN_NAME            = uart
export DESIGN_NICKNAME        = uart-mbff

export VERILOG_FILES          = $(sort $(wildcard $(DESIGN_HOME)/src/uart/*.v))
export SDC_FILE               = $(DESIGN_HOME)/$(PLATFORM)/$(DESIGN_NICKNAME)/constraint.sdc

export PLACE_DENSITY          = 0.5
export DIE_AREA               = 0 0 20 20
export CORE_AREA              = 1.08 1.08 19 19
export TNS_END_PERCENT        = 100
export CLUSTER_FLOPS            = 1

export EQUIVALENCE_CHECK     ?=   1
export REMOVE_CELLS_FOR_EQY   = TAPCELL*
export SKIP_GATE_CLONING      = 1

Step2: I enabled the design in the makefile:

Step3: I executed make and then the error shown in the picture appeared：