diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/gallium/auxiliary/gallivm/f.cpp | 8 | ||||
| -rw-r--r-- | src/gallium/auxiliary/gallivm/lp_bld_arit.c | 65 | ||||
| -rw-r--r-- | src/gallium/drivers/llvmpipe/lp_test_arit.c | 4 |
3 files changed, 43 insertions, 34 deletions
diff --git a/src/gallium/auxiliary/gallivm/f.cpp b/src/gallium/auxiliary/gallivm/f.cpp index 7cb50f16c0f..4b33e49b477 100644 --- a/src/gallium/auxiliary/gallivm/f.cpp +++ b/src/gallium/auxiliary/gallivm/f.cpp @@ -41,11 +41,11 @@ * * and take the coefficients from the P = { ... } array. * - * - To compute log2 5th order polynomial between [1, 2] do: + * - To compute log2 4th order polynomial between [0, 1/9] do: * * variant 1 - * range 1 2 - * order 5 0 + * range 0 0.111111112 + * order 4 0 * step 200 * info * @@ -77,7 +77,7 @@ boost::math::ntl::RR f(const boost::math::ntl::RR& x, int variant) return exp2(x); case 1: - return log2(x)/(x - 1.0); + return log2((1.0 + sqrt(x))/(1.0 - sqrt(x)))/sqrt(x); } return 0; diff --git a/src/gallium/auxiliary/gallivm/lp_bld_arit.c b/src/gallium/auxiliary/gallivm/lp_bld_arit.c index d07cf689de3..4ba4aa54596 100644 --- a/src/gallium/auxiliary/gallivm/lp_bld_arit.c +++ b/src/gallium/auxiliary/gallivm/lp_bld_arit.c @@ -63,7 +63,7 @@ #define EXP_POLY_DEGREE 5 -#define LOG_POLY_DEGREE 5 +#define LOG_POLY_DEGREE 4 /** @@ -2388,41 +2388,38 @@ lp_build_extract_mantissa(struct lp_build_context *bld, /** - * Minimax polynomial fit of log2(x)/(x - 1), for x in range [1, 2[ + * Minimax polynomial fit of log2((1.0 + sqrt(x))/(1.0 - sqrt(x)))/sqrt(x) ,for x in range of [0, 1/9[ * These coefficients can be generate with * http://www.boost.org/doc/libs/1_36_0/libs/math/doc/sf_and_dist/html/math_toolkit/toolkit/internals2/minimax.html */ const double lp_build_log2_polynomial[] = { -#if LOG_POLY_DEGREE == 6 - 3.11578814719469302614, - -3.32419399085241980044, - 2.59883907202499966007, - -1.23152682416275988241, - 0.318212422185251071475, - -0.0344359067839062357313 -#elif LOG_POLY_DEGREE == 5 - 2.8882704548164776201, - -2.52074962577807006663, - 1.48116647521213171641, - -0.465725644288844778798, - 0.0596515482674574969533 +#if LOG_POLY_DEGREE == 5 + 2.88539008148777786488L, + 0.961796878841293367824L, + 0.577058946784739859012L, + 0.412914355135828735411L, + 0.308591899232910175289L, + 0.352376952300281371868L, #elif LOG_POLY_DEGREE == 4 - 2.61761038894603480148, - -1.75647175389045657003, - 0.688243882994381274313, - -0.107254423828329604454 + 2.88539009343309178325L, + 0.961791550404184197881L, + 0.577440339438736392009L, + 0.403343858251329912514L, + 0.406718052498846252698L, #elif LOG_POLY_DEGREE == 3 - 2.28330284476918490682, - -1.04913055217340124191, - 0.204446009836232697516 + 2.88538959748872753838L, + 0.961932915889597772928L, + 0.571118517972136195241L, + 0.493997535084709500285L, #else #error #endif }; - /** * See http://www.devmaster.net/forums/showthread.php?p=43580 + * http://en.wikipedia.org/wiki/Logarithm#Calculation + * http://www.nezumi.demon.co.uk/consult/logx.htm */ void lp_build_log2_approx(struct lp_build_context *bld, @@ -2441,6 +2438,8 @@ lp_build_log2_approx(struct lp_build_context *bld, LLVMValueRef one = LLVMConstBitCast(bld->one, int_vec_type); LLVMValueRef i = NULL; + LLVMValueRef y = NULL; + LLVMValueRef z = NULL; LLVMValueRef exp = NULL; LLVMValueRef mant = NULL; LLVMValueRef logexp = NULL; @@ -2478,18 +2477,28 @@ lp_build_log2_approx(struct lp_build_context *bld, } if(p_log2) { - /* mant = (float) mantissa(x) */ + /* mant = 1 + (float) mantissa(x) */ mant = LLVMBuildAnd(builder, i, mantmask, ""); mant = LLVMBuildOr(builder, mant, one, ""); mant = LLVMBuildBitCast(builder, mant, vec_type, ""); - logmant = lp_build_polynomial(bld, mant, lp_build_log2_polynomial, + /* y = (mant - 1) / (mant + 1) */ + y = lp_build_div(bld, + lp_build_sub(bld, mant, bld->one), + lp_build_add(bld, mant, bld->one) + ); + + /* z = y^2 */ + z = lp_build_mul(bld, y, y); + + /* compute P(z) */ + logmant = lp_build_polynomial(bld, z, lp_build_log2_polynomial, Elements(lp_build_log2_polynomial)); - /* This effectively increases the polynomial degree by one, but ensures that log2(1) == 0*/ - logmant = LLVMBuildFMul(builder, logmant, LLVMBuildFSub(builder, mant, bld->one, ""), ""); + /* logmant = y * P(z) */ + logmant = lp_build_mul(bld, y, logmant); - res = LLVMBuildFAdd(builder, logmant, logexp, ""); + res = lp_build_add(bld, logmant, logexp); } if(p_exp) { diff --git a/src/gallium/drivers/llvmpipe/lp_test_arit.c b/src/gallium/drivers/llvmpipe/lp_test_arit.c index 303042684c1..9b34efed671 100644 --- a/src/gallium/drivers/llvmpipe/lp_test_arit.c +++ b/src/gallium/drivers/llvmpipe/lp_test_arit.c @@ -177,9 +177,9 @@ static const struct unary_test_t unary_tests[] = { {"neg", &lp_build_negate, &negf, exp2_values, Elements(exp2_values), 20.0 }, {"exp2", &lp_build_exp2, &exp2f, exp2_values, Elements(exp2_values), 20.0 }, - {"log2", &lp_build_log2, &log2f, log2_values, Elements(log2_values), 10.0 }, // FIXME + {"log2", &lp_build_log2, &log2f, log2_values, Elements(log2_values), 20.0 }, {"exp", &lp_build_exp, &expf, exp2_values, Elements(exp2_values), 18.0 }, - {"log", &lp_build_log, &logf, log2_values, Elements(log2_values), 10.0 }, // FIXME + {"log", &lp_build_log, &logf, log2_values, Elements(log2_values), 20.0 }, {"rsqrt", &lp_build_rsqrt, &rsqrtf, rsqrt_values, Elements(rsqrt_values), 20.0 }, {"sin", &lp_build_sin, &sinf, sincos_values, Elements(sincos_values), 20.0 }, {"cos", &lp_build_cos, &cosf, sincos_values, Elements(sincos_values), 20.0 }, |