Merge pull request #502 from Gathros/monte_carlo_asm

Monte carlo in X86_64

Author: Gathros

contents/monte_carlo_integration/code/asm-x64/monte_carlo.s

@@ -0,0 +1,88 @@
+.intel_syntax noprefix
+
+.section .rodata
+  pi:            .double 3.141592653589793
+  one:           .double 1.0
+  four:          .double 4.0
+  hundred:       .double 100.0
+  rand_max:      .long 4290772992
+                 .long 1105199103
+  fabs_const:    .long 4294967295
+                 .long 2147483647
+                 .long 0
+                 .long 0
+  estimate_fmt:  .string "The estaimate of pi is %lf\n"
+  error_fmt:     .string "Percentage error: %0.2f\n"
+
+.section .text
+  .global main
+  .extern printf, srand, time, rand
+
+# xmm0 - x
+# xmm1 - y
+# RET rax - bool
+in_circle:
+  mulsd  xmm0, xmm0                  # Calculate x * x + y * y
+  mulsd  xmm1, xmm1
+  addsd  xmm0, xmm1
+  movsd  xmm1, one                   # Set circle radius to 1
+  xor    rax, rax
+  comisd xmm1, xmm0                  # Return bool xmm0 < xmm1
+  seta al
+  ret
+
+# rdi - samples
+# RET xmm0 - estimate
+monte_carlo:
+  pxor   xmm2, xmm2                  # Setting it to zero for loop
+  cvtsi2sd xmm3, rdi                 # From int to double
+  pxor   xmm4, xmm4                  # Setting to zero for counter
+monte_carlo_iter:
+  comisd xmm2, xmm3                  # Check if we went through all samples
+  je     monte_carlo_return
+  call   rand                        # Get random point in the first quartile
+  cvtsi2sd xmm0, rax
+  divsd  xmm0, rand_max
+  call   rand
+  cvtsi2sd xmm1, rax
+  divsd  xmm1, rand_max
+  call   in_circle                   # Check if its in the circle
+  test   rax, rax
+  jz     monte_carlo_false
+  addsd  xmm4, one                   # if so increment counter
+monte_carlo_false:
+  addsd  xmm2, one
+  jmp    monte_carlo_iter
+monte_carlo_return:
+  mulsd  xmm4, four                  # Return estimate
+  divsd  xmm4, xmm2
+  movsd  xmm0, xmm4
+  ret
+
+main:
+  push   rbp
+  sub    rsp, 16
+  mov    rdi, 0
+  call   time
+  mov    rdi, rax
+  call   srand
+  mov    rdi, 1000000
+  call   monte_carlo
+  movsd  QWORD PTR [rsp], xmm0      # Save estimate to stack
+  mov    rdi, OFFSET estimate_fmt   # Print estimate
+  mov    rax, 1
+  call   printf
+  movsd  xmm0, QWORD PTR [rsp]      # Get estimate from stack
+  movsd  xmm1, pi                   # Calculate fabs(M_PI - estimate)
+  subsd  xmm0, xmm1
+  movq   xmm1, fabs_const
+  andpd  xmm0, xmm1
+  divsd  xmm0, pi                   # Print percentage error on pi
+  mulsd  xmm0, hundred
+  mov    rdi, OFFSET error_fmt
+  mov    rax, 1
+  call   printf
+  add    rsp, 16
+  pop    rbp
+  ret
+

contents/monte_carlo_integration/monte_carlo_integration.md

@@ -81,6 +81,8 @@ each point is tested to see whether it's in the circle or not:
 [import:2-4, lang:"lisp"](code/racket/monte_carlo.rkt)
 {% sample lang="scala" %}
 [import:3-3, lang:"scala"](code/scala/monte_carlo.scala)
+{% sample lang="asm-x64" %}
+[import:21-32, lang:"asm-x64"](code/asm-x64/monte_carlo.s)
 {% endmethod %}
 
 If it's in the circle, we increase an internal count by one, and in the end,
@@ -161,6 +163,8 @@ Feel free to submit your version via pull request, and thanks for reading!
 [import, lang:"lisp"](code/racket/monte_carlo.rkt)
 {% sample lang="scala" %}
 [import, lang:"scala"](code/scala/monte_carlo.scala)
+{% sample lang="asm-x64" %}
+[import, lang:"asm-x64"](code/asm-x64/monte_carlo.s)
 {% endmethod %}