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  • VBNC in Mono.

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    At 10:52 AM 13/09/2006 +0200, K P wrote:
    >>But what is the reason for changing some of the .ToString into DirectCast ?
    >
    >If you check for the exact data type (as you did in all the cases I modified
    >to DirectCast) either for value types of for reference types there is no use
    >to do tricky conversions because we know the type of the variable so a
    >DirectCast is the most efficient and most reasonable conversion because
    >after a T <valueIs <typea DirectCast(<value>, <type>) will succeed
    >for sure. So I only suggest to change CType to DirectCast in these contexts.
    In the case of an that is known to contain a String, a call to
    ToString() may perform better than a direct cast. A cast still needs to
    check the type, even though the code has already just done it with a T
    (I'd be very surprised if the JIT can detect that pattern and only do one
    check). Calling .ToString() will be a virtual call to "return this;". It'd
    be interesting to do a comparison, but my intuition is that .ToString()
    would be significantly faster in this case.
    Jonathan Gilbert
    Mono-list maillist - Mono-list (AT) lists (DOT) ximian.com

  • No.1 | | 1177 bytes | |

    Thu, 14 Sep 2006 17:22:34 +0200, Jonathan Gilbert
    <2a5gjx302 (AT) sneakemail (DOT) comwrote:

    In the case of an that is known to contain a String, a call to
    .ToString() may perform better than a direct cast. A cast still needs to
    check the type, even though the code has already just done it with a
    T
    (I'd be very surprised if the JIT can detect that pattern and only do one
    check). Calling .ToString() will be a virtual call to "return this;".
    It'd
    be interesting to do a comparison, but my intuition is that .ToString()
    would be significantly faster in this case.

    Just tried it, but I got inconclusive results (sometimes .ToString()
    performed better, sometimes DirectCast performed better). During the first
    test runs .ToString() did perform better (5-10% better), then suddenly
    DirectCast started performed better (5-20% better), so I don't really
    think there is any big difference. I tried running with and without
    debugger, DEBUG and RELEASE builds, and with and without integer checks
    on, and always got inconclusive results (only on MS, I don't know how Mono
    will perform).

    Rolf

Re: VBNC in Mono.


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