modify_model_interface removing input float tensor is not completed, memory allocator occupied this dummy tensor

1. System information

TFLM
Tensorflow r2.5

2. Code

code in tensorflow\tensorflow\lite\tools\optimize\modify_model_interface.cc

Function: RemoveInputTensor
code: c // Removes the input tensor and the related operator. for (auto tot : inputs) { SubGraphT* subgraph = model->subgraphs.at(tot.subgraph_index).get(); TFLITE_DCHECK(tot.input_index < subgraph->tensors.size()); TFLITE_DCHECK(tot.op_index < subgraph->operators.size()); if (tot.input_index >= original_number_tensors) { subgraph->tensors.erase(subgraph->tensors.begin() + tot.input_index); // DID NOT REMOVED } subgraph->operators.erase(subgraph->operators.begin() + tot.op_index); subgraph->inputs[tot.model_index] = tot.output_index; }

1. We have float input/output from quantization aware model to, reduce tensor arena size, using tool "modify_model_interface" utility convert to int8 - int8.
2. Convert result can run successfully, but memory allocator show unknown scratch buffer used.
   To check it print memory plan enable TF_LITE_SHOW_MEMORY_USE in micro_allocator.cc, that show original float input tensor still exist.
   0 (id=0): size=24576, offset=0, first_used=-1 last_used=-1

I think removing shift all other tensor index in the graph, that could not a easy to remove.
To workaround this I was resizing the dummy float input tensor to smaller one, and keep as it.

Thanks
Jim

Start in tensorflow/tensorflow/lite/tools/optimize/modify_model_interface.cc at RemoveInputTensor, then inspect the memory report enabled by TF_LITE_SHOW_MEMORY_USE in micro_allocator.cc. Reproduce the float-input/output conversion to int8-int8 and verify that the original dummy float input no longer occupies the tensor arena without breaking the converted model.