Root of Unity by SL Huang Page B

don’t believe in guns, okay?” It was an argument we’d been having for months. “Story, end of.”
    “You’ll start believing real fast the day someone shoots you,” I said. “Where are we?”
    He rolled his eyes and started clattering away at a keyboard as he talked. Skinny and hyper, Checker didn’t sacrifice anything in the way of energy to Pilar, though his was more of the manic and terrifying variety. “You’ve got a workstation there,” he said, pointing to a monitor that had just unblanked itself. “If you can pick up tracking the van, I want to keep working on facial recognition on the goons. Nothing useful’s popped so far, but I still have a lot of avenues to try.”
    “I don’t know how your program things work,” I groused, plopping down in the chair Pilar had vacated.
    “Really? Really? You with the superpowered math brain who can figure out the abstraction behind an undocumented program in a night can’t handle doing calculations via a graphical user interface? Quit whining and do it.” He pointed at another monitor. “Go forth and constraint propagate. This is for Arthur, remember.”
    He was right, dammit—I could be pissy later. I told myself it must be the vestiges of the concussion that were still making me grumpy. I rubbed my eyes and took a glance at the way his program was set up—I got a sense of the mathematics right away, the calculus of moving objects, the grid of cameras and other surveillance he could hack into, the ever-expanding search algorithm and, yes, constraint propagation. I fiddled with it for about forty seconds, plugging in different values, and narrowed down his heuristic empirically until the bounds almost touched.
    “You can do a lot better,” I said. “Faster for more likely inputs. If you make it probabilistic—”
    “That’s why I wanted you here,” he interrupted. “Just do it. After this is over, you can help me reprogram the search. I’ll pay you in tequila.”
    We started working. Checker was a bundle of nerves, tapping a pencil against whatever monitor he was at when his fingers weren’t going a mile a minute on the keyboard, and checking his phone every five minutes.
    “Arthur has your number,” I said. “And Pilar hasn’t even gotten there yet.”
    “I know, but what if—” He sighed and took his glasses off, tossing them next to the keyboard in frustration and going back to typing.
    Hell if I knew what he wanted from me. Just like Arthur.
    I kept working, mixing in manual checks of the maps in the area and pulling cherry-picked data from the program’s algorithms to figure into my calculations.
    “Arthur’s lost a lot of people,” Checker said suddenly, a few minutes later. “I’ll be damned if he loses one more, okay?”
    “I didn’t say anything,” I bit out. “I’m helping, aren’t I?”
    “I know. I know. I’m sorry.”
    But Arthur hadn’t thought I’d be willing to jump in, either. He’d probably only forced himself to call me because he was willing to go to hell and back for this woman. To try everything.
    Even me.
    “What is it with him and Halliday, anyway?” I groused.
    “What do you mean?” asked Checker. “He’d do the same for you, or me, or Pilar, or—or anyone else close to him. You know that.”
    I sincerely doubted the part about me. I rubbed my eyes again and reapplied myself to the computer, hating everyone. My head still throbbed.
    Checker stopped typing for a moment and leaned back. “They were best friends since they were about five, okay? Until, uh, a few years ago. They got each other through a lot, as kids. At least from my understanding of it.”
    “Oh, best friends,” I said snidely. “Is that what they’re calling it?”
    “What are you, a thirteen-year-old?” Checker snorted and went back to his keyboard. “I know I’m the last person you expect to say this, but not everything is about sex. Besides, Arthur’s had himself figured out since he was about ten. I’d be very