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base:fastest_multiplication [2023-08-21 05:18] – reposebase:fastest_multiplication [2024-02-13 08:24] (current) – accurate timing if Jack Asser code repose
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 Requires tables or a generator routine such as [[table_generator_routine_for_fast_8_bit_mul_table]] Requires tables or a generator routine such as [[table_generator_routine_for_fast_8_bit_mul_table]]
  
-Jack Asser's: 233* cycles  ref: [[seriously_fast_multiplication]] \\+Jack Asser's: 238.1 cycles  ref: [[seriously_fast_multiplication]] \\
 Chris Jam's: 204.5*  ref: http://csdb.dk/forums/?roomid=11&topicid=91766 \\ Chris Jam's: 204.5*  ref: http://csdb.dk/forums/?roomid=11&topicid=91766 \\
 Mine: 198.6 zp variation: 194.6 \\ Mine: 198.6 zp variation: 194.6 \\
 Times above need to add 6 for rts \\ Times above need to add 6 for rts \\
 Note: updated 2023; corrected code, typos and timings \\ Note: updated 2023; corrected code, typos and timings \\
-*Timing approximate for external code+*Timing approximate for external code \\ 
 +This is the winner out of 120 published algorithms as independently tested here: 
 +https://github.com/TobyLobster/multiply_test \\ 
 +Note: I have a new version which is 188.1 cycles, excepting the RTS. \\
  
 <code> <code>
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 ;How to use: ;How to use:
-;put numbers in x/y and result is Y reg, A reg, z1, z0+;put numbers in x/y and result is Y reg (z3), A reg (z2), z1, z0
  
 ;tables of squares ;tables of squares
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 z0=$80;product, 2 bytes z0=$80;product, 2 bytes
 z1=$81 z1=$81
-z2=$82 ;returned in X reg+z2=$82 ;returned in A reg
 z3=$83 ;returned in Y reg z3=$83 ;returned in Y reg
  
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 lda (p_sqr_hi),y lda (p_sqr_hi),y
 sbc (p_invsqr_hi),y sbc (p_invsqr_hi),y
-tay;x1*y1h;Y=z3, 30.992 cycles+tay;Y=x1*y1h, 30.992 cycles
 ;17+34+33+17+33+31=164.97 cycles for main multiply part (minimum=157, maximum=173) ;17+34+33+17+33+31=164.97 cycles for main multiply part (minimum=157, maximum=173)
  
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 c2a: lda #0 c2a: lda #0
 c2b: adc #0 c2b: adc #0
- tax;X=z2, 6 cycles + tax 
- bcc c1c;3/6 avg 4.5+ bcc c1c;9
  iny;z3++  iny;z3++
- clc+ clc;(+3) taken 7% of the time, 3*.07=+.21
  
 ;-add last number of column 1 ;-add last number of column 1
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 ;-add last number of column 2 ;-add last number of column 2
- txa;A=z2+ txa
 c2c: adc #0 c2c: adc #0
- ;A=z2, 6 + ;A=z2 
- bcc fin;3/4 avg 3.5 + bcc fin;7 
- iny;z3+++ iny;(+1) taken 42% of the time, 1*.42=.42
  
 ;Y=z3, A=z2 ;Y=z3, A=z2
-;33.63 +;add partials part total cycles=33.63 (minimum=33, maximum=37) 
-fin: rts+;total time=164.97+33.63=198.6 
 +fin: rts;add 6 to include this (204.6)
  
 Diagram of the additions Diagram of the additions
base/fastest_multiplication.1692587911.txt.gz · Last modified: 2023-08-21 05:18 by repose