updating README.md

Author: fschlimb

.gitmodules

@@ -1,6 +1,3 @@
 [submodule "third_party/bitsery"]
 	path = third_party/bitsery
 	url = https://github.com/fraillt/bitsery
-[submodule "third_party/mlir-extensions"]
-	path = third_party/mlir-extensions
-	url = https://github.com/intel/mlir-extensions

README.md

@@ -4,21 +4,27 @@ A tensor implementation following the [array API as defined by the data-API cons
 It supports a controller-worker execution model as well as a CSP-like execution.
 
 ## Setting up build environment
-``` bash
+Install MLIR/LLVM and IMEX from branch refactor (see https://github.com/intel/mlir-extensions/tree/refactor).
+```bash
 git --recurse-submodules clone https://github.com/intel-sandbox/personal.fschlimb.ddptensor
 cd personal.fschlimb.ddptensor
 conda env create -f conda-env.yml -n ddpt
 conda activate ddpt
 export MPIROOT=$CONDA_PREFIX
 export MKLROOT=$CONDA_PREFIX
+export MLIRROOT=<your-MLIR-install-dir>
+export IMEXROOT=<your-IMEX-install-dir>
 ```
 ## Building ddptensor
-``` bash
-CC=gcc-9 CXX=g++-9 CMAKE_BUILD_PARALLEL_LEVEL=8 python setup.py develop
+```bash
+python setup.py develop
 ```
+If your compiler does not default to a recent version, try something like `CC=gcc-9 CXX=g++-9 python setup.py develop`
 
 ## Running Tests
-``` bash
+__Test are currently not operational on this branch.__
+
+```bash
 # single rank
 pytest test
 # multiple ranks, controller-worker, controller spawns ranks
@@ -28,3 +34,27 @@ mpirun -n $N python -m pytest test
 # multiple ranks, CSP
 DDPT_CW=0 mpirun -n $N python -m pytest test
 ```
+
+## Running
+```python
+import ddptensor as dt
+dt.init(False)
+a = dt.arange(0, 10, 1, dt.int64)
+#print(a)       # should trigger compilation
+b = dt.arange(0, 100, 10, dt.int64)
+#print(b.dtype) # should _not_ trigger compilation
+c = a * b
+#print(c)
+d = dt.sum(c, [0])
+#del b          # generated function should _not_ return b
+print(a, c, d) # printing of c (not a!) should trigger compilation
+dt.fini()
+```
+Assuming the above is in file `simple.py` a single-process run is executed like
+```bash
+python DDPT_IDTR_SO=`pwd`/ddptensor/libidtr.so python simple.py
+```
+and multi-process run is executed like
+```bash
+python DDPT_IDTR_SO=`pwd`/ddptensor/libidtr.so mpirun -n 5 python simple.py
+```