Another update from ingydotnet^djgoku

Task/Parallel-calculations/Common-Lisp/parallel-calculations-1.lisp

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+(ql:quickload '(lparallel))
+
+(setf lparallel:*kernel* (lparallel:make-kernel 4)) ;; Configure for your system.
+
+(defun factor (n &optional (acc '()))
+  (when (> n 1)
+    (loop with max-d = (isqrt n)
+       for d = 2 then (if (evenp d) (1+ d) (+ d 2)) do
+         (cond ((> d max-d) (return (cons (list n 1) acc)))
+               ((zerop (rem n d))
+                (return (factor (truncate n d)
+                                (if (eq d (caar acc))
+                                    (cons
+                                     (list (caar acc) (1+ (cadar acc)))
+                                     (cdr acc))
+                                    (cons (list d 1) acc)))))))))
+
+(defun max-minimum-factor (numbers)
+  (lparallel:pmap-reduce
+   (lambda (n) (cons n (apply #'min (mapcar #'car (factor n)))))
+   (lambda (a b) (if (> (cdr a) (cdr b)) a b))
+   numbers))
+
+(defun print-max-factor (pair)
+  (format t "~a has the largest miniumum factor ~a~%" (car pair) (cdr pair)))

Task/Parallel-calculations/Common-Lisp/parallel-calculations-2.lisp

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+CL-USER> (print-max-factor (max-minimum-factor '(12757923 12878611 12878893 12757923 15808973 15780709 197622519)))
+12878893 has the largest miniumum factor 47