Custom Query (1030 matches)

I built a hash table with keys that were simple cons cells of the form

(<type> . <item>)

I had a few <type>s, and lots of atomic <item>s (in particular, strings) for each <type>. The performance was very bad.

Investigation showed that ccl::compute-hash-code was returning a hash code that depended only on the <type> but not on the <item>, meaning that hash table look up was degenerating into a linear search.

Example:

(setq h (make-hash-table :test #'equal))

Then

(ccl::compute-hash-code h '(type . "foo") nil)
(ccl::compute-hash-code h '(type . "bar") nil)
(ccl::compute-hash-code h '(type . "baz") nil)
(ccl::compute-hash-code h '(type . pi) nil)
(ccl::compute-hash-code h '(type . nil) nil)

all return exactly the same results.

I wrote some code to exercise CCL's math functions and found that there were cases where intermediate computations were causing floating point overflows.

Functions affected are exp, tan, atan, tanh and atanh:

exp: fails for very large negative real rationals.

tanh: fails for complex arguments with very large real parts.

atanh: fails for numbers of the form 1 + iy for very small y.

tan and atan: analogous failures as for tanh and atanh.

I'm attaching (i) the code to exercise the functions (you just load it into Lisp) and (ii) a file of patches that fix the issues. (Apart from the exp issue, these are present in the fix to 869 - sorry.)

Welcome to Clozure Common Lisp Version 1.9-r15758 (DarwinX8632)!

? (defstruct (foo (:constructor make-foo (mask)))

(mask 0 :type (unsigned-byte 64)))

(make-foo 4177526783)

Error: The value 4177526783 is not of the expected type (UNSIGNED-BYTE 64). While executing: MAKE-FOO, in process listener(1). Type :POP to abort, :R for a list of available restarts. Type :? for other options.