# How to install

## Install from Source
If you encounter some troubles, see [troubleshooting](http://qulacs.org/md_4__trouble_shooting.html).

### Requirements

- python 2.7 or 3.x
- gcc/g++ >= 7.0.0 or VisualStudio 2017
- cmake >= 2.8
- git

### C++ Library(cppsim)

#### GCC
```
git clone https://github.com/qulacs/qulacs.git
cd qulacs
./script/build_gcc.sh
```

#### MSVC
```
git clone https://github.com/qulacs/qulacs.git
cd qulacs
generate_msvc_project.bat
```
Then, open `Project.sln` in `./qulacs/visualstudio/`, and build all.

### Python Interface(Qulacs)

Install
```
git clone https://github.com/qulacs/qulacs.git
cd qulacs
python setup.py install
```

Uninstall
```
pip uninstall qulacs
```

## Getting started

See the following document for more detail.  
[C++ Tutorial](http://qulacs.org/md_2__tutorial__c_p_p.html)  
[Python Tutorial](http://qulacs.org/md_3__tutorial_python.html)   
[Examples](https://github.com/qulacs/quantum-circuits)  
[API document](http://qulacs.org/annotated.html)   

### C++ Libraries

Add `./<qulacs_path>/include/` to include path, and `./<qulacs_path>/lib/` to library path. If you use dynamic link library, add `./<qulacs_path>/bin/` to library path instead.


Example of C++ code:
```cpp
#include <iostream>
#include <cppsim/state.hpp>
#include <cppsim/circuit.hpp>
#include <cppsim/observable.hpp>

int main(){
    QuantumState state(3);
    state.set_Haar_random_state();

    QuantumCircuit circuit(3);
    circuit.add_X_gate(0);
    auto merged_gate = gate::merge(gate::CNOT(0,1),gate::Y(1));
    circuit.add_gate(merged_gate);
    circuit.add_RX_gate(1,0.5);
    circuit.update_quantum_state(&state);

    Observable observable(3);
    observable.add_operator(2.0, "X 2 Y 1 Z 0");
    observable.add_operator(-3.0, "Z 2");
    auto value = observable.get_expectation_value(&state);
    std::cout << value << std::endl;
    return 0;
}
```

Example of build command:

#### GCC
```sh
g++ -O2 -I ./<qulacs_path>/include -L ./<qulacs_path>/lib <your_code>.cpp -lcppsim_static -lcsim_static -fopenmp
```

#### MSVC
```sh
cl -O2 -I ./<qulacs_path>/include <your_code>.cpp ./<qulacs_path>/cppsim_static.lib ./<qulacs_path>/csim_static.lib /openmp
```

### C++ Libraries with GPU

qulacs uses cuBLAS library, so you need to include it.
if you want to use QuantumStateGpu, define `_USE_GPU` to load QuantumStateGpu definitions.

Example of C++ code:
```cpp
#include <iostream>
#include <cppsim/state_gpu.hpp>
#include <cppsim/circuit.hpp>
#include <cppsim/observable.hpp>

int main(){
    QuantumStateGpu state(3);
    state.set_Haar_random_state();

    QuantumCircuit circuit(3);
    circuit.add_X_gate(0);
    auto merged_gate = gate::merge(gate::CNOT(0,1),gate::Y(1));
    circuit.add_gate(merged_gate);
    circuit.add_RX_gate(1,0.5);
    circuit.update_quantum_state(&state);

    Observable observable(3);
    observable.add_operator(2.0, "X 2 Y 1 Z 0");
    observable.add_operator(-3.0, "Z 2");
    auto value = observable.get_expectation_value(&state);
    std::cout << value << std::endl;
    return 0;
}
```

Example of build command:

#### GCC
```sh
nvcc -O2 -I ./<qulacs_path>/include -L ./<qulacs_path>/lib <your_code>.cu -lcppsim_static -lcsim_static -lgpusim_static -D _USE_GPU -lcublas  -Xcompiler -fopenmp 
```

#### MSVC
```sh
nvcc -O2 -I ./<qulacs_path>/include -L ./<qulacs_path>/lib <your_code>.cu ./<qulacs_path>/cppsim_static.lib ./<qulacs_path>/csim_static.lib ./<qulacs_path>/gpusim_static.lib -D _USE_GPU -lcublas  -Xcompiler /openmp 
```


### Python Libraries
You can use features by simply importing `qulacs`.

Example of python code:
```python
from qulacs import Observable, QuantumCircuit, QuantumState
from qulacs.gate import Y,CNOT,merge

state = QuantumState(3)
state.set_Haar_random_state()

circuit = QuantumCircuit(3)
circuit.add_X_gate(0)
merged_gate = merge(CNOT(0,1),Y(1))
circuit.add_gate(merged_gate)
circuit.add_RX_gate(1,0.5)
circuit.update_quantum_state(state)

observable = Observable(3)
observable.add_operator(2.0, "X 2 Y 1 Z 0")
observable.add_operator(-3.0, "Z 2")
value = observable.get_expectation_value(state)
print(value)
```