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- Log ----------------------------------------------------------------- commit 106bf4fc7687741b27523b23db3c9b2443237b2d Author: Raymond Toy toy.raymond@gmail.com Date: Wed Sep 24 19:53:07 2014 -0700

Make the LOG function match what the deftransform for LOG does.

Without this, compiled code produces different answers from interpreted code.

* src/code/irrat.lisp: * Add cases where the base is 2 or 10 to compute the log in the same way as the deftransform for LOG does. * tests/float.lisp: * Fix comparison to use equalp, not equal. * Add test for log10.

diff --git a/src/code/irrat.lisp b/src/code/irrat.lisp index 61d4314..daf6166 100644 --- a/src/code/irrat.lisp +++ b/src/code/irrat.lisp @@ -645,74 +645,112 @@ ;; ANSI spec base) ((and (realp number) (realp base)) - ;; CLHS 12.1.4.1 says - ;; - ;; When rationals and floats are combined by a - ;; numerical function, the rational is first converted - ;; to a float of the same format. - ;; - ;; So assume this applies to floats as well convert all - ;; numbers to the largest float format before computing - ;; the log. - ;; - ;; This makes (log 17 10.0) = (log 17.0 10) and so on. - (number-dispatch ((number real) (base real)) - ((double-float - (foreach double-float single-float)) - (/ (log2 number) (log2 base))) - (((foreach fixnum bignum ratio) - (foreach fixnum bignum ratio single-float)) - (let* ((result (/ (log2 number) (log2 base)))) - ;; Figure out the right result type - (if (realp result) - (coerce result 'single-float) - (coerce result '(complex single-float))))) - (((foreach fixnum bignum ratio) - double-float) - (/ (log2 number) (log2 base))) - ((single-float - (foreach fixnum bignum ratio)) - (let* ((result (/ (log2 number) (log2 base)))) - ;; Figure out the right result type - (if (realp result) - (coerce result 'single-float) - (coerce result '(complex single-float))))) - ((double-float - (foreach fixnum bignum ratio)) - (/ (log2 number) (log2 base))) - ((single-float double-float) - (/ (log (coerce number 'double-float)) (log base))) - #+double-double - ((double-double-float - (foreach fixnum bignum ratio)) - (/ (log2 number 1w0) (log2 base 1w0))) - #+double-double - ((double-double-float - (foreach double-double-float double-float single-float)) - (/ (log number) (log (coerce base 'double-double-float)))) - #+double-double - (((foreach fixnum bignum ratio) - double-double-float) - (/ (log2 number 1w0) (log2 base 1w0))) - #+double-double - (((foreach double-float single-float) - double-double-float) - (/ (log (coerce number 'double-double-float)) (log base))) - (((foreach single-float) - (foreach single-float)) - ;; Converting everything to double-float helps the - ;; cases like (log 17 10) = (/ (log 17) (log 10)). - ;; This is usually handled above, but if we compute (/ - ;; (log 17) (log 10)), we get a slightly different - ;; answer due to roundoff. This makes it a bit more - ;; consistent. + (cond + ((and (= base 2) + (floatp number) + #+double-double + (not (typep number 'ext:double-double-float)) + (or (plusp number) + (eql number 0.0) + (eql number 0d0))) + ;; Do the same thing as the deftranform does for + ;; log base 2 and 10 for non-negative arguments. + (number-dispatch ((number real) (base real)) + ((double-float + (foreach integer single-float double-float)) + (log2 number)) + ((single-float + (foreach integer single-float)) + (float (log2 (float number 1d0)) 1f0)) + ((single-float double-float) + (log2 (float number 1d0))))) + ((and (= base 10) + (floatp number) + #+double-double + (not (typep number 'double-double-float)) + (or (plusp number) + (eql number 0.0) + (eql number 0d0))) + ;; Do the same thing as the deftranform does for + ;; log base 2 and 10 for non-negative arguments. + (number-dispatch ((number real) (base real)) + ((double-float + (foreach double-float single-float integer)) + (%log10 number)) + ((single-float + (foreach single-float integer)) + (float (%log10 (float number 1d0)) 1f0)) + ((single-float double-float) + (%log10 (float number 1d0))))) + (t + ;; CLHS 12.1.4.1 says + ;; + ;; When rationals and floats are combined by a + ;; numerical function, the rational is first converted + ;; to a float of the same format. + ;; + ;; So assume this applies to floats as well convert all + ;; numbers to the largest float format before computing + ;; the log. ;; - ;; FIXME: This probably needs more work. - (let ((result (/ (log (float number 1d0)) - (log (float base 1d0))))) - (if (realp result) - (coerce result 'single-float) - (coerce result '(complex single-float))))))) + ;; This makes (log 17 10.0) = (log 17.0 10) and so on. + (number-dispatch ((number real) (base real)) + ((double-float + (foreach double-float single-float)) + (/ (log2 number) (log2 base))) + (((foreach fixnum bignum ratio) + (foreach fixnum bignum ratio single-float)) + (let* ((result (/ (log2 number) (log2 base)))) + ;; Figure out the right result type + (if (realp result) + (coerce result 'single-float) + (coerce result '(complex single-float))))) + (((foreach fixnum bignum ratio) + double-float) + (/ (log2 number) (log2 base))) + ((single-float + (foreach fixnum bignum ratio)) + (let* ((result (/ (log2 number) (log2 base)))) + ;; Figure out the right result type + (if (realp result) + (coerce result 'single-float) + (coerce result '(complex single-float))))) + ((double-float + (foreach fixnum bignum ratio)) + (/ (log2 number) (log2 base))) + ((single-float double-float) + (/ (log (coerce number 'double-float)) (log base))) + #+double-double + ((double-double-float + (foreach fixnum bignum ratio)) + (/ (log2 number 1w0) (log2 base 1w0))) + #+double-double + ((double-double-float + (foreach double-double-float double-float single-float)) + (/ (log number) (log (coerce base 'double-double-float)))) + #+double-double + (((foreach fixnum bignum ratio) + double-double-float) + (/ (log2 number 1w0) (log2 base 1w0))) + #+double-double + (((foreach double-float single-float) + double-double-float) + (/ (log (coerce number 'double-double-float)) (log base))) + (((foreach single-float) + (foreach single-float)) + ;; Converting everything to double-float helps the + ;; cases like (log 17 10) = (/ (log 17) (log 10)). + ;; This is usually handled above, but if we compute (/ + ;; (log 17) (log 10)), we get a slightly different + ;; answer due to roundoff. This makes it a bit more + ;; consistent. + ;; + ;; FIXME: This probably needs more work. + (let ((result (/ (log (float number 1d0)) + (log (float base 1d0))))) + (if (realp result) + (coerce result 'single-float) + (coerce result '(complex single-float))))))))) (t ;; FIXME: This probably needs some work as well. (/ (log number) (log base)))) diff --git a/tests/float.lisp b/tests/float.lisp index ff07270..eeb221b 100644 --- a/tests/float.lisp +++ b/tests/float.lisp @@ -11,7 +11,13 @@ (decode-float x))) 1d0)))

-(define-test log2 +(define-test log2.interp (loop for k from -1074 to 1023 do (let ((x (scale-float 1d0 k))) - (assert-equal k (log x 2))))) + (assert-equalp k (log x 2))))) + +(define-test log10.interp + (loop for k from 0 to 22 do + (let ((x (float (expt 10 k) 1d0))) + (assert-equalp k (log x 10))))) +

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Summary of changes: src/code/irrat.lisp | 172 +++++++++++++++++++++++++++++++-------------------- tests/float.lisp | 10 ++- 2 files changed, 113 insertions(+), 69 deletions(-)

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