Efficient algorithm for computing the Euler-Poincar\'e characteristic of   a semi-algebraic set defined by few quadratic inequalities
  We present an algorithm which takes as input a closed semi-algebraic set, $S \subset \R^k$, defined by \[ P_1 \leq 0, ..., P_\ell \leq 0, P_i \in \R[X_1,...,X_k], \deg(P_i) \leq 2, \] and computes the Euler-Poincar\'e characteristic of $S$. The complexity of the algorithm is $k^{O(\ell)}$. 
Saugata Basu