Different results running strategy than optimization results

[sfkiwi]

I have a very simple MA strategy but when I run the strategy I get a different result than what I see through the optimizer using the same values:

  # Initialize the MAs
  def __init__(self):
      self.sma_slow = bt.indicators.SimpleMovingAverage(
          self.datas[0], period=self.params.maslow)
        
      self.sma_fast = bt.indicators.SimpleMovingAverage(
          self.datas[0], period=self.params.mafast)

    # Buy if fast cross above slow
    def next(self):
        if not self.position:
            if self.sma_fast[0] > self.sma_slow[0]:
                self.order = self.buy()
        else:
            if self.sma_fast[0] < self.sma_slow[0]:
                self.order = self.sell()

I ran the optimizer

strats = cerebro.optstrategy(
    TestStrategy,
    mafast=range(11, 100),
    maslow=1)

and logged the results

    def stop(self):
        self.log('(MA Fast %2d Slow %2d) Ending Value %.2f' %
                 (self.params.mafast, self.params.maslow, self.broker.getvalue()))

I got the best result as
2000-12-29, (MA Fast 54 Slow 1) Ending Value 1305.80

so I ran the strategy

cerebro.addstrategy(TestStrategy, mafast = 1, maslow = 54, printlog = True)

But I only get a final value of 595.40

print('Final Portfolio Value: %.2f' % cerebro.broker.getvalue())
Final Portfolio Value: 595.40

What could be causing the difference of 1305.80 during the optimization run and 595.40 during the individual strategy run?

[ab_trader]

@sfkiwi according to your output from optimization mafast=54 and maslow=1. Then you run your strategy with mafast = 1, maslow = 54. Maybe this can cause a difference.