Differences

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--- base:fastest_multiplication [2017-04-17 13:55] – repose
+++ base:fastest_multiplication [2017-04-19 09:59] – repose
@@ Line 7: / Line 7: @@
 Jack Asser's: 233 cycles  ref: [[seriously_fast_multiplication]] \\
 Chris Jam's: 204.5  ref: http://csdb.dk/forums/?roomid=11&topicid=91766 \\
-Mine: 201 zp variation: 198 \\
+Mine: 196 zp variation: 192 \\
 Times above need to add 12 for jsr/rts \\
@@ Line 15: / Line 15: @@
 ;and being less elegant and harder to follow.
 ;by Repose 2017
+;table generator by Graham
+;addition improvement suggested by JackAsser
+;data: 2044 bytes
+;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
+;measurement method: branches/page boundary crossings were averaged
+;How to use:
+;put numbers in x/y and result is Y reg, X reg, z1, z0
 ;tables of squares
@@ Line 35: / Line 46: @@
 y0=$fd;multiplicand, 2 bytes
 y1=$fe
-z0=$80;product, 4 bytes
+z0=$80;product, 2 bytes
 z1=$81
-z2=$82
+;z2=$82 returned in X reg
-z3=$83
+;z3=$83 returned in Y reg
 ;Example showing use
@@ Line 153: / Line 164: @@
 lda (p_sqr_hi),y
 sbc (p_invsqr_hi),y
-sta z3;x1*y1h;31
+tay;x1*y1h;Y=z3, 30 cycles
+;17+33+31+17+31+30=159 cycles for main multiply part
-;4*31+2*17 so far=158
+;jmp do_adds; can put do_adds in zp for a slight speed increase
-;add partials
-;-add first two numbers in column 1
-;jmp do_adds;put in zp to save 3 cycles :)
 do_adds:
-clc
+;-add the first two numbers of column 1
-c1a lda #0
+	clc
-c1b adc #0
+c1a:	lda #0
-sta z1;9
+c1b:	adc #0
-;-continue to first two numbers in column 2
+	sta z1;9
-c2a lda #0
-c2b adc #0
+;-continue to first two numbers of column 2
-sta z2;7
+c2a:	lda #0
-bcc c1c;3 taken/9 not taken, avg 6
+c2b:	adc #0
-inc z3
+	tax;X=z2, 6 cycles
-clc
+	bcc c1c;3/6 avg 4.5
-;-add last number of column 1 (row c)
+	iny;z3++
-c1c lda #0
+	clc
-adc z1
-sta z1;8
+;-add last number of column 1
+c1c:	lda #0
+	adc z1
+	sta z1;8
 ;-add last number of column 2
-c2c lda #0
+	txa;A=z2
-adc z2
+c2c:	adc #0
-sta z2;8
+	tax;X=z2, 6
-bcc fin;3/7 avg 5
+	bcc fin;3/4 avg 3.5
-inc z3
+	iny;z3++
-;9+7+6+8+8+5=43
-fin rts
+;Y=z3, X=z2
+;9+6+4.5+8+6+3.5=37
+fin:	rts
 Diagram of the additions