Defining a player's preflop range

A player's range is set in his first preflop decision

A player's preflop range is determined in the first decision he makes preflop.

For example, in our tree we can see that in SB's first decision (the one where he raises to 3) he only raises with the range AA-22,AKs-A2s..., but he does not fold the remaining hands.

In the previous section we discussed that all starting hands had to be accounted for in order for the software to be able to compute the tree. The first decision however, is an exception to this rule. SB will simply be assigned the range AA-22,AKs-A2s... in this hand.

Tip:
Similarly, in BB's first decision, it's also not required to define a strategy for all hands. Please do keep in mind though, that if BB's first decision is not for "all hands" that SB is up against an artificially strong range in hís first decision, which basically renders the data in thát decision almost useless.

The importance of leaving out/adding "fold all hands"

Whether or not you want to add a fold all hands action to a player's first decision will be situation dependent.

If you're working with ranges then you'll probably just want to define all strategies for "all hands".

However, if a player has óne specific combo, then it's rather pointless to let him fold all the other hands.
For example, in the pic below SB raises to 3 with AcKh and folds the remaining 99.9% of the time.
Here, you might as well just leave the "fold all hands" action out.




Working with the Monte Carlo engine?
Now, there is one more spot where you might want to consider working with a predefined range as opposed to "all hands", and that is when you're working with the Monte Carlo engine (click link for more details).

If the Monte Carlo engine is used, then you may want to leave out fold all hands action, in order to prevent a large fraction of your simulations being pointless folds.

For example, in the pic above, SB only raises 8.6% of the time.
If you're working with the Monte Carlo engine here, then you may want to remove the "fold all hands" action.
This will prevent 91.4% of your simulation runs being nothing but folds.