Add README documentation

README.md

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 # merry_mem
-The Robin Hood hash table.
+This project includes a sequential and parallel version of the Robin Hood hash table.
+
+## Project Structure
+
+The project is structured as follows:
+
+```
+|--src/
+|  |--common/           : Common utilities (types and a logger)
+|  |--parallel/         : Parallel implementation (library and simple sanity
+|  |                      check executable)
+|  |--sequential/       : Sequential implementation (library and simple sanity
+|  |                      check executable)
+|  `--traces/           : Code for generating traces to test our implementations
+`--test/
+   |--performance_test/ : Benchmark the sequential vs the parallel parallel
+   |                      implementations with different traces and different
+   |                      numbers of workers
+   |--trace_test/       : Test the trace generating library
+   `--unit_test/        : Unit tests for our sequential and parallel
+                          implementations
+```
+
+## Build
+
+We use the CMake buildsystem (version 3.18.4) that is available on the UG
+machines. After ensuring you have CMake installed, build the CMake project:
+
+```bash
+# In the project's root directory
+mkdir -p build
+cd build
+cmake -S .. -B .
+```
+
+This builds the required `Makefile` that allows you to build the project.
+
+```bash
+# In the build directory
+make
+```
+
+To see the individual targets that can be made, run
+
+```bash
+# In the build directory
+make help
+```
+
+In general, executables are named `*_exe`.
+
+## Test
+
+After building the project, there are three types of tests:
+
+1. Performance tests
+2. Trace tests
+3. Unit tests
+
+Performance tests measure the timing of the sequential and parallel
+implementations when running various traces.
+
+```bash
+#In the build directory
+./test/performance_test/performance_test_exe
+```
+
+Trace tests test the trace generator produces traces in the expected format.
+
+```bash
+# In the build directory
+./test/trace_test/trace_test_exe
+```
+
+Unit tests test that the sequential and parallel implementations match the
+results of the same trace being run on `std::unordered_map`. To run the unit
+tests, run
+
+```bash
+# In the build directory
+./test/unit_test/unit_test_exe
+```
+
+## Performance
+
+After building the performance test, let's run the performance test:
+
+```bash
+#In the build directory
+./test/performance_test/performance_test_exe
+```