c++ - What is best approach for performing operations on pairs of 2d lines? -

so have 10 000 lines defined on 2d plane each line presented (a1, a2, b1, b2) (a, b points). have array of functions need perform on each pair of lines:

angle(a,b)     return atan((b.y-a.y) / (b.x-a.x))   nearlyparallel(angle1, angle2)     delta = abs(angle1-angle2)     return (delta < threshold) or (delta > pi-threshold)  collinear(a,b, c,d)     return nearlyparallel(angle(a,c), angle(b,d)) , nearlyparallel(angle(a,d), angle(b,c)) 

so need line collinear , 1 nearlyparallel each line.

i need in c++ using boost , opensource library needed. under windows in visual studio 2010.

what library, , part can me in organizing fast calculations data? example boost graph lib helpful? mean need perform thread/processors optimizations speeding up. , not have fancy video card perform all...

you use angle function on every line , store result in std::map, using angle key. bring lines similar angles close together, can choose pairs test nearlyparallel , collinear.