Subscriptions are generated based
on one of the templates with the probabilities shown below. SUB_SYMBOL is chosen following a zipf distribution.

All the stock symbols are ranked alphabetically and ranked 1~100. Suppose N is the total number of the subscriptions you need. Then for the ith stock, create
x= [N/(Sigma_1^100 1/i^0.9) * 1/i^0.9] subscriptions for the symbol. The subscriptions may follow one of the following templates with random SUB_HIGH, SUB_LOW and SUB_VOLUME values.

[class,=,`STOCK'],[symbol,=,`SUB_SYMBOL'],[high,>,SUB_HIGH]
[class,=,`STOCK'],[symbol,=,`SUB_SYMBOL'],[low,<,SUB_LOW]
[class,=,`STOCK'],[symbol,=,`SUB_SYMBOL'],[volume,>,SUB_VOLUME]
[class,=,`STOCK'],[symbol,=,`SUB_SYMBOL']
[class,=,`STOCK'],[volume,>,SUB_VOLUME]