mirror of
https://github.com/Asraelite/littlebigcomputer.git
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105 lines
1.5 KiB
Text
105 lines
1.5 KiB
Text
; calculate all primitive pythogorean triples (a^2 + b^2 = c^2) where c <= 32
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nop
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b _start
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results:
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.repeat 0 15
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table:
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.repeat 0 33
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result_index:
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.data 0
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_start:
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li x7, 32 ; limit
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li x0, 1 ; prime
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li x2, 1 ; prime factor bit
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slli x2, x2, 23
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loop_prime:
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addi x0, x0, 1
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bgt x0, x7, squares
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lw x4, table(x0)
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srli x4, x4, 12
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bnez x4, loop_prime
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mv x3, x0 ; multiple
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loop_index:
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lw x4, table(x3) ; x4 = current prime factor bits
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or x4, x4, x2 ; x4 |= add current prime factor bit
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sw x4, table(x3)
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add x3, x3, x0
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ble x3, x7, loop_index
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srli x2, x2, 1 ; update prime bit
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b loop_prime
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squares:
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li x0, 0 ; n
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li x1, 0 ; n^2
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loop_squares:
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lw x4, table(x0) ; 70
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or x4, x4, x1
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sw x4, table(x0)
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add x1, x1, x0
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add x1, x1, x0
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addi x1, x1, 1
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addi x0, x0, 1
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ble x0, x7, loop_squares
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li x0, 1 ; a = 1
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iterate_a:
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addi x0, x0, 1 ; 79
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bgt x0, x7, end
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lw x2, table(x0) ; a^2 (with prime bits)
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mv x6, x0 ; b = a
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iterate_b:
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addi x6, x6, 1 ; 83
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bgt x6, x7, iterate_a
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lw x3, table(x6) ; b^2 (with prime bits)
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and x4, x2, x3 ; check if a and b are coprime
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srli x4, x4, 12
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bnez x4, iterate_b ; 87
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add x3, x2, x3
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andi x3, x3, 0o77 ; a^2 + b^2
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mv x5, x6 ; x5 = c = b
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; x0 = a, x1 = sp, x2 = a^2, x3 = a^2+b^2, x4 = (unused)
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; x5 = c, x6 = b, x7 = limit
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iterate_c:
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addi x5, x5, 1 ; c++ ; 92
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bgt x5, x7, iterate_b
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lw x4, table(x5) ; x4 = c^2|cp
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andi x4, x4, 0o77 ; x4 = c^2
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bgt x4, x3, iterate_b
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bne x5, x3, iterate_c
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; found triple
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; x0 = a, x6 = b, x5 = c
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lw x4, result_index
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sw x0, 0(x4)
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sw x6, 1(x4)
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sw x5, 2(x4)
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addi x4, x4, 3
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sw x4, result_index
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b iterate_a
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end:
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wfi
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