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+How fast *is* Boyer-Moore? Listing 14.1 is a C implementation of
+Boyer-Moore searching; Listing 14.2 is a test-bed program that searches
+up to the first 32K of a file for a pattern. Table 14.1 (all times
+measured with Turbo Profiler on a 20 MHz cached 386, searching a
+modified version of the text of this chapter) shows that this
+implementation is generally much slower than **REPNZ SCASB,** although
+it does come close when searching for long patterns. Listing 14.1 is
+designed primarily to make later assembly implemenmore comprehensible,
+rather than faster; Sedge’s implementation uses arrays rather than
+pointers, is a great deal more compact and very clever, and may be
+somewhat faster. Regardless, the far superior performance of **REPNZ
+SCASB** clearly indicates that assembly language is in order at this
+point.
+
+* * * * *
+
+“g;”
+
+“Yogi”
+
+“igoY”
+
+“Adrian”
+
+“Conclusion”
+
+“You don’t know what you know”
+
+* * * * *
+
+Searching approach
+
+(16K)
+
+(16K)
+
+(16K)
+
+(\<1K)
+
+(16K)
+
+(16K)
+
+REPNZ SCASB on first char a(Listing 9.1)
+
+8.2
+
+7.5
+
+9.7
+
+0.4
+
+7.4
+
+8.1
+
+REPNZ SCASB on least common char (Listing 9.2)
+
+7.6
+
+7.5
+
+7.5
+
+0.5
+
+7.5
+
+7.5
+
+Boyer-Moore in C (Listing 14.1)
+
+71.0
+
+38.4
+
+37.7
+
+1.8
+
+18.2
+
+9.2
+
+Standard Boyer-Moore in ASM(code not shown)
+
+38.5
+
+21.0
+
+20.5
+
+0.8
+
+9.4
+
+4.8
+
+Quick handling of first mismatch Boyer-Moore in ASM(Listing 14.3)
+
+14.1
+
+8.9
+
+7.7
+
+0.4
+
+4.0
+
+2.0
+
+\<=255 pattern length + sentinelBoyer-Moore in ASM(Listing 14.4)
+
+8.1
+
+5.2
+
+4.6
+
+0.3
+
+2.6
+
+1.2
+
+Search pattern (approximate distance searched before match is shown in
+parentheses).\
+ Times are in milliseconds; shorter is better.
+
+* * * * *
+
+Table 14.1 Comparison of searching techniques.
+
+* * * * *
+
+The entry “Standard Boyer-Moore in ASM” in Table 14.1 refers to
+straight-forward hand optimization of Listing 14.1, code that is not
+included in this chapter for the perfectly good reason that it is slower
+in most cases than **REPNZ SCASB.** I say this casually now, but not so
+yesterday, when I had all but concluded that Boyer-Moore was simply
+inferior on the x86, due to two architectural quirks: the string
+instructions and slow branch. I had even coined a neat phrase for it:
+Architecture is destiny. Has a nice ring, doesn’t it?
+
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+  [Previous](14-02.html)   [Table of Contents](index.html)   [Next](14-04.html)
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+
+* * * * *
+
+Graphics Programming Black Book © 2001 Michael Abrash