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我正在使用 ns2 模拟器和 tcl script.on 执行以下代码，它引发了浮点异常错误。在我更改以下代码部分中的速率值之前

$ns duplex-link $n0 $n2 2.0Mb 10ms RED
$ns duplex-link $n1 $n2 2.0Mb 10ms DropTail
$ns duplex-link $n2 $n3 1.1Mb 20ms DropTail
$ns duplex-link $n3 $n2 1.2Mb 10ms DropTail

它工作正常，但在更改为以下内容后，即在我使用变量rate02,rate12,rate23,rate32而不是值之后发生浮点异常。有人可以帮忙吗？

整个tcl代码如下：

    #Create a simulator object

    set ns [new Simulator]

    global set rate02 2.0Mb 
    global set rate12 2.0Mb
    global set rate23 1.1Mb
    global set rate32 1.2Mb

    #Define different colors for data flows (for NAM)
    $ns color 1 Blue
    $ns color 2 Red
    $ns color 3 Green

    #Open the NAM trace file
    set nf [open out.nam w]
    $ns namtrace-all $nf

    #Define a 'finish' procedure
    proc finish {} {
        global ns nf
        $ns flush-trace
        #Close the NAM trace file
        close $nf
        #Execute NAM on the trace file
        exec nam out.nam &
        exit 0
    }

    #Create four nodes
    set n0 [$ns node]
    set n1 [$ns node]
    set n2 [$ns node]
    set n3 [$ns node]

    #Create links between the nodes
    $ns duplex-link $n0 $n2 rate02 10ms RED
    $ns duplex-link $n1 $n2 rate12 10ms DropTail
    $ns duplex-link $n2 $n3 rate23 20ms DropTail
    $ns duplex-link $n3 $n2 rate32 10ms DropTail

        #Set Queue Size of link (n2-n3) to 10
        $ns queue-limit $n2 $n3 20
        $ns queue-limit $n3 $n2 22

        #Give node position (for NAM)
        $ns duplex-link-op $n0 $n2 orient right-down
        $ns duplex-link-op $n1 $n2 orient right-up
        $ns duplex-link-op $n2 $n3 orient right

        #Monitor the queue for link (n2-n3). (for NAM)
        $ns duplex-link-op $n2 $n3 queuePos 0.5


        #Setup a TCP connection
        set tcp1 [new Agent/TCP]
        $tcp1 set class_ 2
        $ns attach-agent $n0 $tcp1
        set sink [new Agent/TCPSink]
        $ns attach-agent $n3 $sink
        $ns connect $tcp1 $sink
        $tcp1 set fid_ 1
        #########################################
        #Setup a TCP connection
        set tcp3 [new Agent/TCP]
        $tcp3 set class_ 2
        $ns attach-agent $n3 $tcp3
        set sink2 [new Agent/TCPSink]
        $ns attach-agent $n2 $sink2
        $ns connect $tcp3 $sink2
        $tcp3 set fid_ 3

        #Setup a FTP over TCP connection
        set ftp3 [new Application/FTP]
        $ftp3 attach-agent $tcp3
        $ftp3 set type_ FTP
        ############################################
        #Setup a FTP over TCP connection
        set ftp1 [new Application/FTP]
        $ftp1 attach-agent $tcp1
        $ftp1 set type_ FTP

        #Setup a TCP connection
        set tcp2 [new Agent/TCP]
        $tcp2 set class_ 2
        $ns attach-agent $n1 $tcp2
        set sink [new Agent/TCPSink]
        $ns attach-agent $n3 $sink
        $ns connect $tcp2 $sink
        $tcp2 set fid_ 2

        #Setup a FTP over TCP connection
        set ftp2 [new Application/FTP]
        $ftp2 attach-agent $tcp2
        $ftp2 set type_ FTP

         proc openTrace { stopTime testName } {
            $self instvar ns_
            exec rm -f out.tr temp.rands
            set traceFile [open out.tr w]
            puts $traceFile "v testName $testName"
            $ns_ at $stopTime \
                "close $traceFile ; $self finish $testName"
            return $traceFile
        }
        proc traceQueues { node traceFile } {
            $self instvar ns_
            foreach nbr [$node neighbors] {
                $ns_ trace-queue $node $nbr $traceFile
                [$ns_ link $node $nbr] trace-dynamics $ns_ $traceFile
            }
        }


        #Schedule events for the CBR and FTP agents
        $ns at 0.1 "$ftp2 start"
        $ns at 1.0 "$ftp1 start"
        $ns at 1.0 "$ftp3 start"
        $ns at 4.0 "$ftp2 stop"
        $ns at 4.5 "$ftp1 stop"
        $ns at 4.5 "$ftp3 stop"

        #Detach tcp and sink agents (not really necessary)
        $ns at 4.5 "$ns detach-agent $n0 $tcp1 ; $ns detach-agent $n3 $sink"
        $ns at 4.5 "$ns detach-agent $n1 $tcp2 ; $ns detach-agent $n3 $sink"

        #Call the finish procedure after 5 seconds of simulation time
        $ns at 5.0 "finish"
        $ns run
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1 回答 1

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除非那个“NS2”的东西重新定义了 Tcl 的global命令，否则脚本应该是这样的：

#Create a simulator object

set ns [new Simulator]

set rate02 2.0Mb 
set rate12 2.0Mb
set rate23 1.1Mb
set rate32 1.2Mb

# ...

#Create links between the nodes
$ns duplex-link $n0 $n2 $rate02 10ms RED
$ns duplex-link $n1 $n2 $rate12 10ms DropTail
$ns duplex-link $n2 $n3 $rate23 20ms DropTail
$ns duplex-link $n3 $n2 $rate32 10ms DropTail

# ...

换句话说，您的代码存在两个问题：

  • Tclglobal命令的语义定义为global varname ?varname ...?，也就是说，它只是将传递给它的名称声明为引用全局变量。因此，调用只声明名称“set”、“rate02”和“2.0Mb”来表示全局变量。很可能不是你想要的。global set rate02 2.0Mb
  • 子duplex-link命令可能需要一个值作为它的“rate”参数，并且您正在向它传递一个变量的名称。 看起来，一些 NS2 代码然后尝试将这样的字符串解释为浮点值，但由于明显的原因而失败。因此，当您想将该变量的值传递给命令时，您必须取消引用该变量以获取其值。这是使用命令或使用语法set varname的速记符号完成的：（有关此的更多信息）。$$varname

看起来您应该从处理这些基础知识的 Tcl 教程开始。

于 2012-06-21T15:26:17.533 回答