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197 lines
7.6 KiB
HTML
197 lines
7.6 KiB
HTML
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<HTML>
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<HEAD>
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<TITLE>timesoftfloat</TITLE>
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</HEAD>
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<BODY>
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<H1>Berkeley TestFloat Release 3e: <CODE>timesoftfloat</CODE></H1>
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<P>
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John R. Hauser<BR>
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2018 January 20<BR>
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</P>
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<H2>Overview</H2>
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<P>
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The <CODE>timesoftfloat</CODE> program provides a simple way to evaluate the
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speed of the floating-point operations of the Berkeley SoftFloat library.
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Program <CODE>timesoftfloat</CODE> is included with the Berkeley TestFloat
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package, a small collection of programs for testing that an implementation of
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floating-point conforms to the IEEE Standard for Binary Floating-Point
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Arithmetic.
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Although <CODE>timesoftfloat</CODE> does not test floating-point correctness
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like the other TestFloat programs, nevertheless <CODE>timesoftfloat</CODE> is a
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partner to TestFloat’s <CODE>testsoftfloat</CODE> program.
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For more about TestFloat generally and <CODE>testsoftfloat</CODE> specifically,
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see file
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<A HREF="TestFloat-general.html"><NOBR><CODE>TestFloat-general.html</CODE></NOBR></A>.
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</P>
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<P>
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Ordinarily, <CODE>timesoftfloat</CODE> will measure a function’s speed
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separately for each of the five rounding modes defined by the IEEE
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Floating-Point Standard, one after the other, plus possibly a sixth mode,
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<I>round to odd</I> (depending on the options selected when
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<CODE>timesoftfloat</CODE> was compiled).
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If an operation is not supposed to require rounding, it will by default be
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timed only with the rounding mode set to <CODE>near_even</CODE> (nearest/even).
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In the same way, if an operation is affected by the way in which underflow
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tininess is detected, <CODE>timesoftfloat</CODE> times the function with
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tininess detected both before rounding and after rounding.
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For <NOBR>80-bit</NOBR> double-extended-precision operations affected by
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rounding precision control, <CODE>timesoftfloat</CODE> also times the function
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for each of the three rounding precision modes, one after the other.
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Evaluation of a function can be limited to a single rounding mode, a single
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tininess mode, and/or a single rounding precision with appropriate command-line
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options.
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</P>
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<P>
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For each function and mode evaluated, <CODE>timesoftfloat</CODE> reports the
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measured speed of the function in Mop/s, or “millions of operations per
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second”.
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The speeds reported by <CODE>timesoftfloat</CODE> may be affected somewhat by
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other software executing at the same time as <CODE>timesoftfloat</CODE>.
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Be aware also that the exact execution time of any SoftFloat function depends
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partly on the values of arguments and the state of the processor’s caches
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at the time the function is called.
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Your actual experience with SoftFloat may differ from the speeds reported by
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<CODE>timesoftfloat</CODE> for all these reasons.
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</P>
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<P>
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Note that the remainder operations for larger formats (<CODE>f64_rem</CODE>,
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<CODE>extF80_rem</CODE>, and <CODE>f128_rem</CODE>) can be markedly slower than
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other operations, particularly for double-extended-precision
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(<CODE>extF80_rem</CODE>) and quadruple precision (<CODE>f128_rem</CODE>).
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This is inherent to the remainder operation itself and is not a failing of the
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SoftFloat implementation.
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</P>
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<H2>Command Syntax</H2>
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<P>
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The <CODE>timesoftfloat</CODE> program is executed as a command with this
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syntax:
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<BLOCKQUOTE>
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<PRE>
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timesoftfloat [<<I>option</I>>...] <<I>function</I>>
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</PRE>
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</BLOCKQUOTE>
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Square brackets (<CODE>[ ]</CODE>) denote optional arguments,
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<CODE><<I>option</I>></CODE> is a supported option, and
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<CODE><<I>function</I>></CODE> is the name of either a testable function
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or a function set.
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The available options and function sets are documented below.
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If <CODE>timesoftfloat</CODE> is executed without any arguments, a summary of
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usage is written.
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</P>
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<H2>Options</H2>
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<P>
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The <CODE>timesoftfloat</CODE> program accepts several command options.
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If mutually contradictory options are given, the last one has priority.
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</P>
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<H3><CODE>-help</CODE></H3>
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<P>
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The <CODE>-help</CODE> option causes a summary of program usage to be written,
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after which the program exits.
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</P>
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<H3><CODE>-precision32, -precision64, -precision80</CODE></H3>
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<P>
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For <NOBR>80-bit</NOBR> double-extended-precision funcions affected by
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rounding precision control, the <CODE>-precision32</CODE> option restricts
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timing of an operation to only the cases in which the rounding precision is
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<NOBR>32 bits</NOBR>, equivalent to <NOBR>32-bit</NOBR> single-precision.
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Other rounding precision choices are not timed.
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Likewise, <CODE>-precision64</CODE> fixes the rounding precision to
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<NOBR>64 bits</NOBR>, equivalent to <NOBR>64-bit</NOBR> double-precision;
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and <CODE>-precision80</CODE> fixes the rounding precision to the full
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<NOBR>80 bits</NOBR> of the double-extended-precision format.
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All these options are ignored for operations not affected by rounding precision
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control.
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</P>
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<H3><CODE>-rnear_even, -rnear_maxMag, -rminMag, -rmin, -rmax, -rodd</CODE></H3>
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<P>
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The <CODE>-rnear_even</CODE> option restricts timing of an operation to only
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the cases in which the rounding mode is nearest/even.
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Other rounding mode choices are not timed.
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Likewise, <CODE>-rnear_maxMag</CODE> forces rounding to nearest/maximum
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magnitude (nearest-away), <CODE>-rminMag</CODE> forces rounding to minimum
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magnitude (toward zero), <CODE>-rmin</CODE> forces rounding to minimum (down,
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toward negative infinity), <CODE>-rmax</CODE> forces rounding to maximum (up,
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toward positive infinity), and <CODE>-rodd</CODE>, if supported, forces
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rounding to odd.
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These options are ignored for operations that are exact and thus do not round.
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</P>
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<H3><CODE>-tininessbefore, -tininessafter</CODE></H3>
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<P>
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The <CODE>-tininessbefore</CODE> option restricts timing of an operation to
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only the cases in which tininess on underflow is detected before rounding.
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Likewise, <CODE>-tininessafter</CODE> restricts measurement to only the cases
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in which tininess on underflow is detected after rounding.
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</P>
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<H3><CODE>-notexact, -exact</CODE></H3>
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<P>
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For functions that round to an integer (conversions to integer types and the
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<CODE>roundToInt</CODE> functions), the <CODE>-notexact</CODE> option restricts
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timing of an operation to only the cases for which the
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<CODE><I>exact</I></CODE> operand (specifying whether the <I>inexact</I>
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exception flag may be raised) is <CODE>false</CODE>.
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Likewise, the <CODE>-exact</CODE> option restricts measurement to only the
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cases for which the <CODE><I>exact</I></CODE> operand is <CODE>true</CODE>.
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</P>
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<H2>Function Sets</H2>
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<P>
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Just as <CODE>timesoftfloat</CODE> can time a function for all five or six
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rounding modes in sequence, multiple functions can be timed with a single
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execution of <CODE>timesoftfloat</CODE>.
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Three sets are recognized:
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<CODE>-all1</CODE>, <CODE>-all2</CODE>, and <CODE>-all</CODE>.
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The set <CODE>-all1</CODE> is all one-operand operations, <CODE>-all2</CODE> is
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all two-operand operations, and <CODE>-all</CODE> is obviously all operations.
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A function set is used in place of a function name in the
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<CODE>timesoftfloat</CODE> command line, such as
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<BLOCKQUOTE>
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<PRE>
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timesoftfloat [<<I>option</I>>...] -all1
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</PRE>
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</BLOCKQUOTE>
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</P>
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<P>
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For the purpose of deciding the number of operands of an operation, any
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<CODE><I>roundingMode</I></CODE> and <CODE><I>exact</I></CODE> arguments are
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ignored.
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(Such arguments specify the rounding mode and whether the <I>inexact</I>
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exception flag may be raised, respectively.)
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Thus, functions that convert to integer type and the <CODE>roundToInt</CODE>
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functions are included in the set of one-operand operations timed by
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<CODE>-all1</CODE>.
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</P>
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</BODY>
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