digitalmars.D.bugs - [Issue 3749] New: cannot evaluate ylog2x at compile time
- d-bugmail puremagic.com (31/31) Jan 28 2010 http://d.puremagic.com/issues/show_bug.cgi?id=3749
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- d-bugmail puremagic.com (12/18) Jan 28 2010 http://d.puremagic.com/issues/show_bug.cgi?id=3749
- d-bugmail puremagic.com (157/157) Jan 28 2010 http://d.puremagic.com/issues/show_bug.cgi?id=3749
- d-bugmail puremagic.com (45/45) Jan 31 2010 http://d.puremagic.com/issues/show_bug.cgi?id=3749
- d-bugmail puremagic.com (122/122) May 12 2010 http://d.puremagic.com/issues/show_bug.cgi?id=3749
- d-bugmail puremagic.com (6/6) May 12 2010 http://d.puremagic.com/issues/show_bug.cgi?id=3749
- d-bugmail puremagic.com (9/9) Nov 15 2010 http://d.puremagic.com/issues/show_bug.cgi?id=3749
- d-bugmail puremagic.com (15/15) Dec 05 2010 http://d.puremagic.com/issues/show_bug.cgi?id=3749
- d-bugmail puremagic.com (12/12) Jan 15 2013 http://d.puremagic.com/issues/show_bug.cgi?id=3749
http://d.puremagic.com/issues/show_bug.cgi?id=3749 Summary: cannot evaluate ylog2x at compile time Product: D Version: 2.041 Platform: Other OS/Version: Linux Status: NEW Severity: normal Priority: P2 Component: DMD AssignedTo: nobody puremagic.com ReportedBy: baryluk smp.if.uj.edu.pl 12:19:56 PST --- import std.stdio; import std.math; double iter(double x) { static immutable a = log(4.0); return x*a; } void main() { writefln("%s", iter(5.0)); } /usr/include/d/dmd2-posix/phobos/import/std/math.d(1415): Error: cannot evaluate yl2x(x,0xb.17217f7d1cf79acp-4L) at compile time aaaa.d(6): Error: cannot evaluate log(4L) at compile time aaaa.d(6): Error: cannot evaluate log(4L) at compile time This also means that currently DMD compiler will not perform constant folding on a. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Jan 28 2010
http://d.puremagic.com/issues/show_bug.cgi?id=3749 12:29:09 PST --- Same problem is with exp function. /usr/include/d/dmd2-posix/phobos/import/std/math.d(895): Error: cannot evaluate exp2(0xb.8aa3b295c17f0bcp-3L * x) at compile time /usr/include/d/dmd2-posix/phobos/import/std/math.d(903): Error: cannot evaluate exp(cast(real)x) at compile time aaaa.d(6): Error: cannot evaluate exp(4F) at compile time aaaa.d(6): Error: cannot evaluate exp(4F) at compile time I know it can solved by using CTFE functions, but for example sqrt or sin, cos are working correctly. I really don't want to put by hand obscure numerical constants, and then don't know from where they came :) Releated to bug1475. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Jan 28 2010
http://d.puremagic.com/issues/show_bug.cgi?id=3749 Witold Baryluk <baryluk smp.if.uj.edu.pl> changed: What |Removed |Added ---------------------------------------------------------------------------- Severity|normal |minor -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Jan 28 2010
http://d.puremagic.com/issues/show_bug.cgi?id=3749 David Simcha <dsimcha yahoo.com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |dsimcha yahoo.com A patch has just been submitted fairly recently for if(__ctfe). Once that's released, people (myself included) will start submitting patches to make compile-time versions of most of std.math. Most of the runtime implementations use assembly language somewhere for efficiency, or call the C standard lib implementations. We'll have to write more naive compile-time versions of these functions. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Jan 28 2010
http://d.puremagic.com/issues/show_bug.cgi?id=3749 Don <clugdbug yahoo.com.au> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |clugdbug yahoo.com.auA patch has just been submitted fairly recently for if(__ctfe). Once that's released, people (myself included) will start submitting patches to make compile-time versions of most of std.math. Most of the runtime implementations use assembly language somewhere for efficiency, or call the C standard lib implementations. We'll have to write more naive compile-time versions of these functions.if(__ctfe) is in the next release. yl2x() probably should have built-in support, though. Since it's an intrinsic, if (__ctfe) won't work for it. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Jan 28 2010
http://d.puremagic.com/issues/show_bug.cgi?id=3749 15:55:35 PST --- So I release this as public domain. I written this code as workaround to lack of log and exp. They looks to be accurate to 16 digital digits on whole real line. Results can be slightly different than values returned by std.math.{log,exp} unfortunetly. Anybody want to review this code or know better methods? /** Calculate natural logarithm of x. * * * Performs reduction of large values to (0..3) inverval, using log(x 3^n) = log(x) + n*log(3) * * Then uses truncated Taylor series in variable y=(x-1)/(x+1) for x > 0. * * For values x < 1, calculate -log(1/x) * */ double ctfe_log(double x_) { if (x_ == 0.0) { return -double.infinity; } if (x_ < 0.0) { return double.nan; } if (x_ == double.infinity) { return double.infinity; } if (x_ == 1.0) { return 0.0; } if (!(x_ == x_)) { // nan return double.nan; } real x = x_; if (x > 1.0) { uint m = 0; // reduce to (1 .. 3) interval while (x > 3.0) { x = x / 3.0; m = m + 1; } real y = (x-1.0)/(x+1.0); real y2 = y*y; /* Evaluate Horner's scheme on polynomial * log(x) = log((1+y) / (1-y)) = 2 y (1 + y^2/3 + y^4/5 + y^6/7 + ... y^70/71) */ real temp = 0.0; for (int i = 71; i >= 3; i -= 2) { temp += 1.0/cast(real)i; temp *= y2; } temp += 1.0; y = 2.0*y*temp; if (m) { return y + m*ctfe_log(3.0); } else { return y; } } else { return -ctfe_log(1.0/x); } } /** Compute exponential function of x. * * Uses truncated Taylor series expeansion of exp function. * * Performs reduction for |x| > 2, of the form exp(x 2^m) = exp(x)^(2^m) */ double ctfe_exp(double x_) { if (x_ == 0.0) { return 1.0; } if (x_ >= 710.0) { // includes +infinity return double.infinity; } if (x_ <= -746.0) { // includes -infinity return 0.0; } if (!(x_ == x_)) { // nan return double.nan; } real x = x_; int m = 0; // reduce to (-2 .. 2) interval if (x > 0.0) { while (x > 2.0) { x = x / 2.0; m = m + 1; } } else { while (x < -2.0) { x = x / 2.0; m = m - 1; } } real temp = 1.0; real term = 1.0; for (int i = 1; i <= 25; i++) { term *= x/cast(real)i; temp += term; } if (m) { real exp2 = ctfe_exp(2.0); if (m > 0) { for (int i = 0; i < m; i++) { temp = temp*temp; } } else { for (int i = 0; i < -m; i++) { temp = temp*temp; } } return temp; } else { return temp; } } int tests(double[] xs, int min, int max) { assert(min <= max); int r = 0; double c = 1.0; if (min < 0) { for (int i = 0; i < -min; i++) { c = c / 2.0; } } if (min > 0) { for (int i = 0; i < -min; i++) { c = c * 2.0; } } for (int i = min; i <= max; i++) { foreach (x0; xs) { auto x = c * x0; if ( (ctfe_exp(ctfe_log(x)) - x) / x < 1.0e-16 ) { // ok } else { r = r + 1; } } } return r; } enum c = tests( [0.1, 0.1001, 0.11, 0.2, 0.24, 0.3, 0.341, 0.387123, 0.4, 0.5, 0.55, 0.6, 0.7, 0.732, 0.8, 0.88, 0.9, 0.98, 0.9991, 0.999992], -300, 300); static assert(c == 0); static assert(ctfe_exp(0.0) == 1.0); static assert(ctfe_exp(-1000.0) == 0.0); static assert(ctfe_exp(1000.0) == double.infinity); static assert(ctfe_log(0.0) == -double.infinity); -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Jan 28 2010
http://d.puremagic.com/issues/show_bug.cgi?id=3749 08:03:28 PST --- Small but important error in unittest (c was not multiplied correctly. Also -300..300 range was somehow too big, compilations was very long. int tests(double[] xs, int min, int max) { assert(min <= max); int r = 0; double c = 1.0; if (min < 0) { for (int i = 0; i < -min; i++) { c = c / 2.0; } } if (min > 0) { for (int i = 0; i < min; i++) { c = c * 2.0; } } for (int i = min; i <= max; i++) { foreach (x0; xs) { auto x = c * x0; if ( (ctfe_exp(ctfe_log(x)) - x) / x < 1.0e-16 ) { ; } else { r = r + 1; } } c = c * 2.0; } return r; } unittest { enum c = tests( [0.1, 0.1001, 0.11, 0.2, 0.24, 0.3, 0.341, 0.387123, 0.4, 0.5, 0.55, 0.6, 0.7, 0.732, 0.8, 0.88, 0.9, 0.98, 0.9991, 0.999992], -30, 30); static assert(c == 0); } static assert(ctfe_exp(0.0) == 1.0); static assert(ctfe_exp(-1000.0) == 0.0); static assert(ctfe_exp(1000.0) == double.infinity); static assert(ctfe_log(0.0) == -double.infinity); -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Jan 31 2010
http://d.puremagic.com/issues/show_bug.cgi?id=3749 bearophile_hugs eml.cc changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |bearophile_hugs eml.cc For a generic compile-time function fit to be used with D FP types, it can be better to use reals everywhere: /** Calculate natural logarithm of x. * * Performs reduction of large values to (0..3) inverval, using * log(x 3^n) = log(x) + n*log(3) * * Then uses truncated Taylor series in variable y=(x-1)/(x+1) for x > 0. * * For values x < 1, calculate -log(1/x) * */ real ctfe_log(real x_) { if (x_ == 0.0) { return -real.infinity; } if (x_ < 0.0) { return real.nan; } if (x_ == real.infinity) { return real.infinity; } if (x_ == 1.0) { return 0.0; } if (!(x_ == x_)) { // nan return real.nan; } real x = x_; if (x > 1.0) { uint m = 0; // reduce to (1 .. 3) interval while (x > 3.0) { x = x / 3.0; m = m + 1; } real y = (x-1.0)/(x+1.0); real y2 = y*y; /* Evaluate Horner's scheme on polynomial * log(x) = log((1+y) / (1-y)) = 2 y (1 + y^2/3 + y^4/5 + y^6/7 + ... y^70/71) */ real temp = 0.0; for (int i = 71; i >= 3; i -= 2) { temp += 1.0/cast(real)i; temp *= y2; } temp += 1.0; y = 2.0*y*temp; if (m) { return y + m*ctfe_log(3.0); } else { return y; } } else { return -ctfe_log(1.0/x); } } /** Compute exponential function of x. * * Uses truncated Taylor series expeansion of exp function. * * Performs reduction for |x| > 2, of the form exp(x 2^m) = exp(x)^(2^m) */ real ctfe_exp(real x_) { if (x_ == 0.0) { return 1.0; } if (x_ >= 710.0) { // includes +infinity return real.infinity; } if (x_ <= -746.0) { // includes -infinity return 0.0; } if (!(x_ == x_)) { // nan return real.nan; } real x = x_; int m = 0; // reduce to (-2 .. 2) interval if (x > 0.0) { while (x > 2.0) { x = x / 2.0; m = m + 1; } } else { while (x < -2.0) { x = x / 2.0; m = m - 1; } } real temp = 1.0; real term = 1.0; for (int i = 1; i <= 25; i++) { term *= x/cast(real)i; temp += term; } if (m) { real exp2 = ctfe_exp(2.0); if (m > 0) { for (int i = 0; i < m; i++) { temp = temp*temp; } } else { for (int i = 0; i < -m; i++) { temp = temp*temp; } } return temp; } else { return temp; } } -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
May 12 2010
http://d.puremagic.com/issues/show_bug.cgi?id=3749 See bug 4177 for a blocker of this. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
May 12 2010
http://d.puremagic.com/issues/show_bug.cgi?id=3749 --- Created an attachment (id=811) PATCH against rev 755 add support for yl2x, yl2xp1 Implements yl2x, yl2xp1 as builtins for DMC, VisualStudio. Needs implementation for GCC -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Nov 15 2010
http://d.puremagic.com/issues/show_bug.cgi?id=3749 Walter Bright <bugzilla digitalmars.com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |bugzilla digitalmars.com Severity|minor |enhancement 22:31:08 PST --- I'm going to defer this until there's a reasonably portable implementation of the specifics of yl2x and yl2xp1. Probably one can be built out of the C standard library math functions. Failing that, we'll need an inline asm version for gcc, and a 64 bit inline version. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Dec 05 2010
http://d.puremagic.com/issues/show_bug.cgi?id=3749 Martin Nowak <code dawg.eu> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |code dawg.eu What's the state of this? Having log/exp functions at compile time would be very useful, e.g. to pregenerate scientific tables. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Jan 15 2013