CHECK: Computing C = A + B for sparse vectors A and B
CHECK-NEXT: A (2,10) (3,60) (5,20) (8,40) 
CHECK-NEXT: B (1,50) (2,30) (4,80) (5,30) (7,90) (8,10) 
CHECK-NEXT: C (1,50) (2,40) (3,60) (4,80) (5,50) (7,90) (8,50)