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