In a comment to the previous article on a case insensitive hash code, Stefan Glienke pointed to an approach used in Spring4D’s comparers, which is a delightful hack.
Rather than converting the string to a “proper lower case”, it converts the string to an “approximate lower case” using an “or $20”, which happens to be good enough for a hash on string identifiers.
To figure the trick, one needs to check the ASCII Table. (more…)
Recent commits to the DWScript repository doubled the compiler performance when compiling many small scripts, like happens in the unit tests suites.
This started from a first profiling run where the memory allocations around the UnicodeLowerCase function came out as top bottlenecks.
Thing is, Pascal being a case-insensitive language, there are lots of case-insensitive comparisons, lookups, searches and hashes, and turns out a key hash code was computed with code like
Here I will share my current workflow for low-level optimization, which these days is basically a roundtrip between Delphi, SamplingProfiler, ChatGPT and Godbolt.
This can allow you to produce code that runs faster than any single C compiler, while staying with Delphi code. (more…)
Just created a new repository with a “LibCBLAS” unit meant to use the OpenBLAS library in its Windows 64bit incarnation from Delphi 10.3+
https://bitbucket.org/egrange/libcblas/
OpenBLAS is an optimized BLAS library (Basic Linear Algebra Subprograms), the DLL itself can be obtained from the “xianyi” repository where pre-compiled Windows DLL are maintained.
It occurred to me that SHA-3 being a cryptographic hash, it is one of those peculiar bits of code that are fully self-testing. Any bug in a cryptographic hash will quickly cascade to a different result, no matter the bug or the input.
This means the ad-hoc-compiler-monkey can be unleashed “safely”, and can be allowed to try “improper changes.”
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A new kernel for SHA-3 (Keccak) cryptographic hashing has been committed to the DWScript repository.
It is almost 3 times faster than the Pascal version, makes use of MMX asm, and involved an “ad hoc compiler”.
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A trivial way to turn a case-sensitive String hash function into a case-insensitive one is to to pass a lower-case (or upper-case) version of the String.
However, in our days of Unicode strings, this is not innocuous…
Following a recent post by A. Bouchez about an optimized CRC32 hash, I took it as an opportunity to re-run a small String Hashing Shootout on the worst hash function collision torture test I know: ZIP codes in UTF-16 (Delphi’s default String format).
In a Google+ comment to my recent article about inlining in XE6, Leif Uneus posted results from Scimark.
It appears that XE6 is about 30% slower than previous versions at least from XE5 to XE for 32bits floating point.
Note that Scimark does not make use of inlining, but does make heavy use of floating-point computations, loops and arrays.
Edit: issue discussed here was reported in QC 124652 (now marked as resolved)
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First noticed by dewresearch, Delphi XE6 introduced a new optimization for inlined functions that return a floating-point value.
Here is an exploration of what was improved… and what was not improved.
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