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--- base:fastest_multiplication [2023-08-21 04:54] – repose
+++ base:fastest_multiplication [2024-02-13 08:24] (current) – accurate timing if Jack Asser code repose
@@ Line 5: / Line 5: @@
 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: 196 zp variation: 192 \\
+Mine: 198.6 zp variation: 194.6 \\
-Times above need to add 12 for jsr/rts \\
+Times above need to add 6 for rts \\
-Note: updated 2023; corrected typos and timings \\
+Note: updated 2023; corrected code, typos and timings \\
+*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>
@@ Line 22: / Line 26: @@
 ;zero page ram required: minimum 8 bytes, ideally 14
 ;do_add: 30 bytes in zp, if used
-;time: 196 cycles, option for 192 if you use 30 more zp bytes for do_add
+;time: 198.6 cycles, option for 194.6 if you use 30 more zp bytes for do_add
 ;measurement method: average timings over all input combinations
 ;How to use:
-;put numbers in x/y and result is Y reg, X reg, z1, z0
+;put numbers in x/y and result is Y reg (z3), A reg (z2), z1, z0
 ;tables of squares
 ;sqr(x)=x^2/4
 ;negsqr(x)=(255-x)^2/4
-sqrlo=$c000;511 bytes
+sqrlo=$c100;511 bytes
-sqrhi=$c200;511 bytes
+sqrhi=$c300;511 bytes
-negsqrlo=$c400;511 bytes
+negsqrlo=$c500;511 bytes
-negsqrhi=$c600;511 bytes
+negsqrhi=$c700;511 bytes
 ;pointers to square tables above
@@ Line 49: / Line 53: @@
 z0=$80;product, 2 bytes
 z1=$81
-z2=$82 ;returned in X reg
+z2=$82 ;returned in A reg
 z3=$83 ;returned in Y reg
 ;Example showing use
+*=$c000
 lda #$ff
 sta x0
@@ Line 60: / Line 65: @@
 jsr makesqrtables
 jsr umult16
-stx z2
+sta z2
 sty z3
+rts
 ;result should be $fffe0001, e.g. as viewed with a typical m 0080 monitor command:
 ;0080 01 00 fe ff
@@ Line 167: / Line 173: @@
 lda (p_sqr_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)
@@ Line 181: / Line 187: @@
 c2a:	lda #0
 c2b:	adc #0
-	tax;X=z2, 6 cycles
+	tax
-	bcc c1c;3/6 avg 4.5
+	bcc c1c;9
 	iny;z3++
-	clc
+	clc;(+3) taken 7% of the time, 3*.07=+.21
 ;-add last number of column 1
@@ Line 192: / Line 198: @@
 ;-add last number of column 2
-	txa;A=z2
+	txa
 c2c:	adc #0
-	tax;X=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, X=z2
+;Y=z3, A=z2
-;9+6+4.5+8+6+3.5=37
+;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