Update cta_backtester.md

2019-05-08 22:18:56 +08:00 · 2019-05-08 22:18:56 +08:00 · 539e7aca1e
commit 539e7aca1e
parent 1d8e7c6897
1 changed files with 269 additions and 1 deletions
--- a/docs/cta_backtester.md
+++ b/docs/cta_backtester.md
@ -102,8 +102,129 @@ def run_backtesting(
 &nbsp;

 ## 参数优化
+vnpy提供2种参数优化的解决方案：穷举算法、遗传算法

-参数优化功能使用的是穷举算法，即多进程对所有参数组合进行回测，并输出最终解集。其操作流程如下：
+
+&nbsp;
+
+### 穷举算法
+
+穷举算法原理：
+- 输入需要优化的参数名、优化区间、优化步进，以及优化目标。
+```
+    def add_parameter(
+        self, name: str, start: float, end: float = None, step: float = None
+    ):
+        """"""
+        if not end and not step:
+            self.params[name] = [start]
+            return
+
+        if start >= end:
+            print("参数优化起始点必须小于终止点")
+            return
+
+        if step <= 0:
+            print("参数优化步进必须大于0")
+            return
+
+        value = start
+        value_list = []
+
+        while value <= end:
+            value_list.append(value)
+            value += step
+
+        self.params[name] = value_list
+
+    def set_target(self, target_name: str):
+        """"""
+        self.target_name = target_name
+```
+
+&nbsp;
+
+
+- 形成全局参数组合, 数据结构为[{key: value, key: value}, {key: value, key: value}]。
+```
+    def generate_setting(self):
+        """"""
+        keys = self.params.keys()
+        values = self.params.values()
+        products = list(product(*values))
+
+        settings = []
+        for p in products:
+            setting = dict(zip(keys, p))
+            settings.append(setting)
+
+        return settings
+```
+&nbsp;
+
+
+- 遍历全局中的每一个参数组合：遍历的过程即运行一次策略回测，并且返回优化目标数值；然后根据目标数值排序，输出优化结果。
+```
+    def run_optimization(self, optimization_setting: OptimizationSetting, output=True):
+        """"""
+        # Get optimization setting and target
+        settings = optimization_setting.generate_setting()
+        target_name = optimization_setting.target_name
+
+        if not settings:
+            self.output("优化参数组合为空，请检查")
+            return
+
+        if not target_name:
+            self.output("优化目标未设置，请检查")
+            return
+
+        # Use multiprocessing pool for running backtesting with different setting
+        pool = multiprocessing.Pool(multiprocessing.cpu_count())
+
+        results = []
+        for setting in settings:
+            result = (pool.apply_async(optimize, (
+                target_name,
+                self.strategy_class,
+                setting,
+                self.vt_symbol,
+                self.interval,
+                self.start,
+                self.rate,
+                self.slippage,
+                self.size,
+                self.pricetick,
+                self.capital,
+                self.end,
+                self.mode
+            )))
+            results.append(result)
+
+        pool.close()
+        pool.join()
+
+        # Sort results and output
+        result_values = [result.get() for result in results]
+        result_values.sort(reverse=True, key=lambda result: result[1])
+
+        if output:
+            for value in result_values:
+                msg = f"参数：{value[0]}, 目标：{value[1]}"
+                self.output(msg)
+
+        return result_values
+```
+
+
+
+
+注意：可以使用multiprocessing库来创建多进程实现并行优化。例如：若用户计算机是2核，优化时间为原来1/2；若计算机是10核，优化时间为原来1/10。
+
+&nbsp;
+
+
+穷举算法操作：

 - 点击“参数优化”按钮，会弹出“优化参数配置”窗口，用于设置优化目标（如最大化夏普比率、最大化收益回撤比）和设置需要优化的参数以及优化区间，如图。
  
@ -118,6 +239,153 @@ def run_backtesting(
 ![](https://vnpy-community.oss-cn-shanghai.aliyuncs.com/forum_experience/yazhang/cta_backtester/optimize_result.png)


+&nbsp;
+
+### 遗传算法
+
+遗传算法原理：
+
+- 输入需要优化的参数名、优化区间、优化步进，以及优化目标；
+
+- 形成全局参数组合，该组合的数据结构是列表内镶嵌元组，即[[(key, value), (key, value)] , [(key, value), (key,value)]]，与穷举算法的全局参数组合的数据结构不同。这样做的目的是有利于参数间进行交叉互换和变异。
+```
+    def generate_setting_ga(self):
+        """""" 
+        settings_ga = []
+        settings = self.generate_setting()     
+        for d in settings:            
+            param = [tuple(i) for i in d.items()]
+            settings_ga.append(param)
+        return settings_ga
+```
+
+&nbsp;
+
+
+- 形成个体：调用random()函数随机从全局参数组合中获取参数。
+```
+        def generate_parameter():
+            """"""
+            return random.choice(settings)
+```
+
+&nbsp;
+
+
+- 定义个体变异规则: 即发生变异时，旧的个体完全被新的个体替代。
+```
+        def mutate_individual(individual, indpb):
+            """"""
+            size = len(individual)
+            paramlist = generate_parameter()
+            for i in range(size):
+                if random.random() < indpb:
+                    individual[i] = paramlist[i]
+            return individual,
+```
+
+&nbsp;
+
+
+- 定义评估函数：入参的是个体，即[(key, value), (key, value)]形式的参数组合，然后通过dict()转化成setting字典，然后运行回测，输出目标优化数值，如夏普比率、收益回撤比。(注意，修饰器@lru_cache作用是缓存计算结果，避免遇到相同的输入重复计算，大大降低运行遗传算法的时间)
+```
+@lru_cache(maxsize=1000000)
+def _ga_optimize(parameter_values: tuple):
+    """"""
+    setting = dict(parameter_values)
+
+    result = optimize(
+        ga_target_name,
+        ga_strategy_class,
+        setting,
+        ga_vt_symbol,
+        ga_interval,
+        ga_start,
+        ga_rate,
+        ga_slippage,
+        ga_size,
+        ga_pricetick,
+        ga_capital,
+        ga_end,
+        ga_mode
+    )
+    return (result[1],)
+
+
+def ga_optimize(parameter_values: list):
+    """"""
+    return _ga_optimize(tuple(parameter_values))
+```
+
+&nbsp;
+
+- 运行遗传算法：调用deap库的算法引擎来运行遗传算法，其具体流程如下。
+1）先定义优化方向，如夏普比率最大化；
+2）然后随机从全局参数组合获取个体，并形成族群；
+3）对族群内所有个体进行评估（即运行回测），并且剔除表现不好个体；
+4）剩下的个体会进行交叉或者变异，通过评估和筛选后形成新的族群；（到此为止是完整的一次种群迭代过程）；
+5）多次迭代后，种群内差异性减少，整体适应性提高，最终输出建议结果。该结果为帕累托解集，可以是1个或者多个参数组合。
+
+注意：由于用到了@lru_cache, 迭代中后期的速度回提高非常多，因为很多重复的输入都避免了再次的回测，直接在内存中查询并且返回计算结果。
+```
+from deap import creator, base, tools, algorithms
+creator.create("FitnessMax", base.Fitness, weights=(1.0,))
+creator.create("Individual", list, fitness=creator.FitnessMax)
+        ......
+        # Set up genetic algorithem
+        toolbox = base.Toolbox() 
+        toolbox.register("individual", tools.initIterate, creator.Individual, generate_parameter)                          
+        toolbox.register("population", tools.initRepeat, list, toolbox.individual)                                            
+        toolbox.register("mate", tools.cxTwoPoint)                                               
+        toolbox.register("mutate", mutate_individual, indpb=1)               
+        toolbox.register("evaluate", ga_optimize)                                                
+        toolbox.register("select", tools.selNSGA2)       
+
+        total_size = len(settings)
+        pop_size = population_size                      # number of individuals in each generation
+        lambda_ = pop_size                              # number of children to produce at each generation
+        mu = int(pop_size * 0.8)                        # number of individuals to select for the next generation
+
+        cxpb = 0.95         # probability that an offspring is produced by crossover    
+        mutpb = 1 - cxpb    # probability that an offspring is produced by mutation
+        ngen = ngen_size    # number of generation
+                
+        pop = toolbox.population(pop_size)      
+        hof = tools.ParetoFront()               # end result of pareto front
+
+        stats = tools.Statistics(lambda ind: ind.fitness.values)
+        np.set_printoptions(suppress=True)
+        stats.register("mean", np.mean, axis=0)
+        stats.register("std", np.std, axis=0)
+        stats.register("min", np.min, axis=0)
+        stats.register("max", np.max, axis=0)
+
+        algorithms.eaMuPlusLambda(
+            pop, 
+            toolbox, 
+            mu, 
+            lambda_, 
+            cxpb, 
+            mutpb, 
+            ngen, 
+            stats,
+            halloffame=hof
+        )
+
+        # Return result list
+        results = []
+
+        for parameter_values in hof:
+            setting = dict(parameter_values)
+            target_value = ga_optimize(parameter_values)[0]
+            results.append((setting, target_value, {}))
+        
+        return results
+```
+
+
+
+