mirror of
https://github.com/RTimothyEdwards/magic.git
synced 2026-08-29 09:30:46 +02:00
Tim Edwards
09577b5636
The website documentation now points to these contents in a clone of the repository on opencircuitdesign.com, so all future edits of the command-line documentation will be made directly to the git repository. Also: Changed the precision of box values printed in microns from 2 to 3 digits after the decimal place, so that 5 nanometer grids do not get values clipped in the output.
82 lines
2.7 KiB
HTML
82 lines
2.7 KiB
HTML
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</HEAD>
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<TITLE>Magic-7.3 Command Reference</TITLE>
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<BODY BACKGROUND=graphics/blpaper.gif>
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<H1> <IMG SRC=graphics/magic_title8_2.png ALT="Magic VLSI Layout Tool Version 8.3">
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<IMG SRC=graphics/magic_OGL_sm.gif ALIGN="top" ALT="*"> </H1>
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<H2>random</H2>
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<HR>
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Generate a random number or set a random seed.
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<HR>
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<H3>Usage:</H3>
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<BLOCKQUOTE>
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<B>random</B> [<B>seed</B> [<I>value</I>]]<BR><BR>
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<BLOCKQUOTE>
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where <I>value</I> is any integer.
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</BLOCKQUOTE>
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</BLOCKQUOTE>
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<H3>Summary:</H3>
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<BLOCKQUOTE>
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The <B>random</B> command with no arguments generates and returns a
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random integer value. With option <B>seed</B> and no additional
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argument, it sets the random seed value according to the current
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time. With option <B>seed</B> and additional argument <I>value</I>,
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it sets the random seed to the specified value. <P>
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When used with option <B>seed</B>, no value is returned. <P>
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Random numbers are generally frowned upon in layout because they
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can make certain things non-reproducible from run to run. Magic
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uses random numbers in only one very restricted circumstance,
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for GDS output. The use in GDS output is restricted to the
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single circumstance of writing an entire GDS file
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due to use of the "GDS_FILE" property in a cell with a "GDS_START"
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property value of "0". Because the GDS file may contain cells of
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unknown names, and these names could collide with names in the
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database, the GDS file cells are all prefixed with a random
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two-character string. To prevent the same prefix from being
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used on any run of magic, the random number generator should be
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appropriately seeded. <P>
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Note that there is no random number seeding on startup of magic,
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so if needed, the random seed should be set in the startup file
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or on the command line. <P>
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</BLOCKQUOTE>
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<H3>Implementation Notes:</H3>
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<BLOCKQUOTE>
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<B>random</B> is implemented as a built-in <B>magic</B> command.
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</BLOCKQUOTE>
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<H3>See Also:</H3>
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<BLOCKQUOTE>
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<A HREF=gds.html><B>gds</B></A> <BR>
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</BLOCKQUOTE>
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<P><IMG SRC=graphics/line1.gif><P>
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<TABLE BORDER=0>
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<TR>
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<TD> <A HREF=commands.html>Return to command index</A>
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</TR>
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</TABLE>
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<P><I>Last updated:</I> January 15, 2021 at 1:00pm <P>
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</BODY>
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