Rand16 (Events)

#   ROUTINE: rand16
#   SUMMARY: 16-bit linear congruential pseudorandom number generator, using well-known constants made (in)famous by Peter Grogono in 1978.
#   
#   nextRNG = (prevRNG * 25173 + 13849) mod 2^16
#
0014a48c: 3c048017 lui r4,0x8017
0014a490: 8c843c7c lw r4,0x3c7c(r4)			2 words after next event(?). Previous RNG value, might be specific to events.
0014a494: 00000000 nop
0014a498: 00041840 sll r3,r4,0x01			r4 * 2
0014a49c: 00641821 addu r3,r3,r4			r4 * 3
0014a4a0: 00031100 sll r2,r3,0x04			r4 * 30
0014a4a4: 00621821 addu r3,r3,r2			r4 * 33
0014a4a8: 00031880 sll r3,r3,0x02			r4 * 204
0014a4ac: 00641823 subu r3,r3,r4			r4 * 203
0014a4b0: 00031140 sll r2,r3,0x05			r4 * 6496
0014a4b4: 00431023 subu r2,r2,r3			r4 * 6293
0014a4b8: 00021080 sll r2,r2,0x02			r4 * 25172             # No idea what the purpose of building this constant this way is.
0014a4bc: 00441021 addu r2,r2,r4			r4 * 25173             # Perhaps to intentionally waste cycles to slow this down?
0014a4c0: 24423619 addiu r2,r2,0x3619			r4 * 0x6254 + 0x3619
0014a4c4: 3042ffff andi r2,r2,0xffff			efficient modulo via bitmask
0014a4c8: 3c018017 lui r1,0x8017
0014a4cc: ac223c7c sw r2,0x3c7c(r1)			update the RNG seed
0014a4d0: 03e00008 jr r31
0014a4d4: 00000000 nop