\(\newcommand{\W}[1]{ \; #1 \; }\) \(\newcommand{\R}[1]{ {\rm #1} }\) \(\newcommand{\B}[1]{ {\bf #1} }\) \(\newcommand{\D}[2]{ \frac{\partial #1}{\partial #2} }\) \(\newcommand{\DD}[3]{ \frac{\partial^2 #1}{\partial #2 \partial #3} }\) \(\newcommand{\Dpow}[2]{ \frac{\partial^{#1}}{\partial {#2}^{#1}} }\) \(\newcommand{\dpow}[2]{ \frac{ {\rm d}^{#1}}{{\rm d}\, {#2}^{#1}} }\)
base_hash¶
View page sourceBase Type Requirements for Hash Coding Values¶
Syntax¶
hash_code ( x )Purpose¶
CppAD uses a table of Base type values when recording
AD < Base > operations.
A hashing function is used to reduce number of values stored in this table;
for example, it is not necessary to store the value 3.0 every
time it is used as a Parameter .
Default¶
The default hashing function works with the set of bits that correspond
to a Base value.
In most cases this works well, but in some cases
it does not. For example, in the
base_adolc.hpp case, an adouble value can have
fields that are not initialized and valgrind reported an error
when these are used to form the hash code.
x¶
This argument has prototype
const
Base&x
It is the value we are forming a hash code for.
code¶
The return value code has prototype
unsigned shortcode
It is the hash code corresponding to x . This intention is the commonly used values will have different hash codes. The hash code must satisfy
code <
CPPAD_HASH_TABLE_SIZE
so that it is a valid index into the hash code table.
inline¶
If you define this function, it should declare it to be inline ,
so that you do not get multiple definitions from different compilation units.