How to make the engine extremely aggressive or defensive ?

[MahmoudUthman]

Especially against humans ?

[Dann Corbit]

Especially against humans ?

Castle opposite and pawn storm.
Add bonus to keep the pawn formations open.
Add bonus to trade when equal.
Raise contempt to a high value.

[jdart]

My king safety score is based primarily on how well-protected the King is by pawns (King cover), and how many/what types of pieces are attacking the king.

These can be pretty easily tuned up or down. Right now they are set so that the program doesn't usually sacrifice a piece to open up the opposing King or to generate an attack, unless it looks like there will be substantial compensation. But if you give more reward for those factors, it will start to make sacrifices and in that respect play more aggressively.

--Jon

[Vinvin]

Especially against humans ?

Castle opposite and pawn storm.
Add bonus to keep the pawn formations open.
Add bonus to trade when equal.
Raise contempt to a high value.

I understand the 3 other but not this one : "Add bonus to trade when equal.".
From my experience it's better to hold pieces to build an attack. Trading pieces would simplify the position.

[Daniel Anulliero]

Especially against humans ?

Add bonus to trade when equal
.

Don't you mean " trade when ahead In material instead" ?

[Vinvin]

Especially against humans ?

Add bonus to trade when equal
.

Don't you mean " trade when ahead In material instead" ?

The general rule in chess is :
"Trade pieces but not pawns when ahead in material"
and the correlation : "Trade pawns but not pieces when behind in material".
The idea is to reach a drawish endgame.