(42S) matrix permanent

01152024, 02:45 PM
(This post was last modified: 01162024 04:54 PM by Werner.)
Post: #3




RE: (42S) matrix permanent
Hi, Albert!
The SQRT is a quick way to turn a 4 into a 2 ;) The only part, I think, that requires some explanation is lines 2351. There, I determine j and dj (+/2) from k, as John Keith explained. So, j is the place of the least significant bit in k. Let >>k be k shifted right till the least significant bit is 1, then dj=2 if >>k MOD 4 equals 3, else dj=2 (I *add* dj*Mj, so my signs are swapped). I also technically calculate the permanent of the transposed matrix, which is of course the same  to save a TRANS(M) which on a 42S will duplicate the matrix. I subsequently fetch the jth *column* of M instead of the row. Instead of trying to find the least significant bit of k, successively dividing by 2, I perform k MOD 4 right away, and use GTO IND ST X to branch off:  half of the time, it is either 1 or 3 and we're done (j=1 and dj=2 for 1 and 2 for 3).  if it is 0, divide k by 4, add 2 to j and loop  if it is 2, add 1 to j, and k MOD 8 is now 2 or 6, and dj 2 or 2, respectively I had a version using v,f and d vectors (even one using only the stack), but this latest version runs almost twice as fast, also because I store the vector v in REGS, so that I don't need to switch indexing/editing matrices, and the calculation of product(v) is faster. Cheers, Werner 41CVâ€ ,42S,48GX,49G,DM42,DM41X,17BII,15CE,DM15L,12C,16CE 

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Messages In This Thread 
(42S) matrix permanent  Werner  01152024, 12:33 PM
RE: (42S) matrix permanent  Albert Chan  01152024, 02:24 PM
RE: (42S) matrix permanent  Werner  01152024 02:45 PM
RE: (42S) matrix permanent  Albert Chan  01152024, 04:06 PM
RE: (42S) matrix permanent  Werner  01152024, 04:22 PM
RE: (42S) matrix permanent  Albert Chan  01162024, 01:00 AM
RE: (42S) matrix permanent  Werner  01162024, 08:47 AM
RE: (42S) matrix permanent  Albert Chan  01162024, 12:24 PM
RE: (42S) matrix permanent  John Keith  01172024, 08:17 PM
RE: (42S) matrix permanent  John Keith  01262024, 10:28 PM

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