The goal of a machine learning regression problem is to predict a single numeric value. For example, you might want to predict the credit score of a person based on age, bank account balance, annual salary, and so on.
The simplest type of regression technique is linear regression. The prediction equation is y’ = (w0 * x0) + (w1 * x1) + . . + b, where the xi are predictor values, and the wi are constants called weights (or coefficients), and the b is a constant called the bias (or intercept).
Training is the process of finding values of the weights and the bias so that predicted y’ values closely match actual target y values in a set of training data. There are several ways to train a linear regression model. Two of the most common are stochastic gradient descent (SGD) training, and pseudo-inverse training.
With SGD training, the weights and bias are initialized to small random values and then iteratively modified to get closer and closer to optimal values, where optimal means minimal mean squared error between predicted y’ values and actual y values. SGD requires a learning rate (typically about 0.01) that moderates how quickly the weights and bias change, and a maximum epochs value (typically about 100 or 1000). The learning rate and maximum epochs must be determined by trial and error.
With pseudo-inverse training, the pseudo-inverse of the matrix of training x values is computed, and then the weights and bias values are computed by multiplying the pseudo-inverse times the target y values. This approach does not require any parameters but computing the pseudo-inverse of a matrix is much more complicated than SGD training.
There are two main approaches to compute a pseudo-inverse: singular value decomposition (SVD), and QR decomposition.
There are two main categories of algorithms to compute an SVD pseudo-inverse: bidiagonalization techniques and Jacobi techniques, and both have many variations.
There are three main algorithms to compute a QR pseudo-inverse: Householder, modified Gram-Schmidt, and Givens. Each has several variations.
In short, there are dozens of ways to compute a pseudo-inverse for linear regression training. The techniques vary in complexity, precision, and performance. There is no single best way to do linear regression training because if there was one best way, there’d be only one way, not dozens.
I put together a demo of linear regression that uses pseudo-inverse training via QR decomposition using the modified Gram-Schmidt technique. This approach has medium complexity, medium precision, and medium performance and is usually a good approach for training datasets that have fewer than 2,000 items. SGD training works for very large datasets but then you have to find good values for the learning rate and maximum epochs.
For my demo, I used a set of synthetic data that was generated by a neural network with small random weights and biases. The data looks like:
-0.1660, 0.4406, -0.9998, -0.3953, -0.7065, 0.4840 0.0776, -0.1616, 0.3704, -0.5911, 0.7562, 0.1568 -0.9452, 0.3409, -0.1654, 0.1174, -0.7192, 0.8054 0.9365, -0.3732, 0.3846, 0.7528, 0.7892, 0.1345 . . .
The first five values on each line are predictors. The last value on each line is the target y value to predict. There are 200 training items and 40 test items.
The output of my demo is:
Begin C# linear regression using pseudo-inverse (QR Gram-Schmidt) training Loading synthetic train (200) and test (40) data Done First three train X: -0.1660 0.4406 -0.9998 -0.3953 -0.7065 0.0776 -0.1616 0.3704 -0.5911 0.7562 -0.9452 0.3409 -0.1654 0.1174 -0.7192 First three train y: 0.4840 0.1568 0.8054 Creating and training Linear Regression model using QR p-inverse Done Coefficients/weights: -0.2656 0.0333 -0.0454 0.0358 -0.1146 Bias/constant: 0.3619 Evaluating model Accuracy train (within 0.10) = 0.4600 Accuracy test (within 0.10) = 0.6500 MSE train = 0.0026 MSE test = 0.0020 Predicting for x = -0.1660 0.4406 -0.9998 -0.3953 -0.7065 Predicted y = 0.5329 End demo
The accuracy of the linear regression model is poor because the synthetic data has complex, non-linear interactions between variables. Linear regression doesn’t always work well, but it’s almost always a good way to start a regression analysis. In the very worst case, linear regression provides a baseline result for comparison with more powerful, but complicated, techniques such as kernel ridge regression, gradient boost regression, and neural network regression.
The TrainPinv() method is self-contained so that it can be swapped out by an SGD version:
public void TrainPinv(double[][] trainX, double[] trainY)
{
int dim = trainX[0].Length;
this.weights = new double[dim]; // w = pinv(dX) * y
// 1. compute desgn matrix X from trainX
// 2. compute pseudo-inv of X using QR
// a. compute Q and R
// b. compute inv(Q) and inv(R)
// c. compute Xpinv = Qinv * Rinv
// 3. compute wts-bias vector = Xpinv * trainY
// 4. extract and store wts and bias from the vector
}
The design matrix code adds a leading column of 1.0 values to the trainX matrix to account for the bias. The pseudo-inverse code does a lot of work. After multiplying the pseudo-inverse of the design matrix times the vector of training y values, the resulting vector holds the bias at cell [0] (because of the column of 1.0 values) and the weights in cells [1], [2] . . etc.
When linear regression training via pseudo-inverse works, it’s preferable to SGD training because pseudo-inverse doesn’t require parameters (learning rate, max epochs) that must be determined by trial and error. However, computing the pseudo-inverse is very tricky and it can fail (numeric overflow, or underflow) for pathological cases of training data.
Good fun.

My favorite series of science fiction books is the Mars series by Edgar Rice Burroughs. I like the simple, linear story lines.
The fourth book in the series is “Thuvia, Maid of Mars” (1916). The story is about Cathoris, the son of John Carter and Dejah Thoris, as he sets out to rescue Princess Thuvia who has been kidnapped.
Left: Cover art by Robert Abbett. Center: Cover art by Roy Krenkel. Right: Cover art by Michael Whelan.
Demo program. Replace “lt” (less than), “gt”, “lte”, “gte” with Boolean operator symbols (my blog editor chokes on symbols).
using System;
using System.IO;
using System.Collections.Generic;
namespace LinearRegressionPinv
{
internal class LinearRegressionPinvProgram
{
static void Main(string[] args)
{
Console.WriteLine("\nBegin C# linear regression" +
" using pseudo-inverse (QR-GS) training ");
// 1. load data
Console.WriteLine("\nLoading synthetic train" +
" (200) and test (40) data");
string trainFile =
"..\\..\\..\\Data\\synthetic_train_200.txt";
int[] colsX = new int[] { 0, 1, 2, 3, 4 };
double[][] trainX =
MatLoad(trainFile, colsX, ',', "#");
double[] trainY =
MatToVec(MatLoad(trainFile,
new int[] { 5 }, ',', "#"));
string testFile =
"..\\..\\..\\Data\\synthetic_test_40.txt";
double[][] testX =
MatLoad(testFile, colsX, ',', "#");
double[] testY =
MatToVec(MatLoad(testFile,
new int[] { 5 }, ',', "#"));
Console.WriteLine("Done ");
Console.WriteLine("\nFirst three train X: ");
for (int i = 0; i "lt" 3; ++i)
VecShow(trainX[i], 4, 8);
Console.WriteLine("\nFirst three train y: ");
for (int i = 0; i "lt" 3; ++i)
Console.WriteLine(trainY[i].ToString("F4").
PadLeft(8));
// 2. create and train model using pseudo-inverse
Console.WriteLine("\nCreating and training" +
" Linear Regression model using QR p-inverse ");
LinearRegressor model = new LinearRegressor();
model.TrainPinv(trainX, trainY);
Console.WriteLine("Done ");
// 2b. show model parameters
Console.WriteLine("\nCoefficients/weights: ");
for (int i = 0; i "lt" model.weights.Length; ++i)
Console.Write(model.weights[i].ToString("F4") + " ");
Console.WriteLine("\nBias/constant: " +
model.bias.ToString("F4"));
// 3. evaluate model
Console.WriteLine("\nEvaluating model ");
double accTrain = model.Accuracy(trainX, trainY, 0.10);
Console.WriteLine("\nAccuracy train (within 0.10) = " +
accTrain.ToString("F4"));
double accTest = model.Accuracy(testX, testY, 0.10);
Console.WriteLine("Accuracy test (within 0.10) = " +
accTest.ToString("F4"));
double mseTrain = model.MSE(trainX, trainY);
Console.WriteLine("\nMSE train = " +
mseTrain.ToString("F4"));
double mseTest = model.MSE(testX, testY);
Console.WriteLine("MSE test = " +
mseTest.ToString("F4"));
// 4. use model to predict first training item
double[] x = trainX[0];
Console.WriteLine("\nPredicting for x = ");
VecShow(x, 4, 9);
double predY = model.Predict(x);
Console.WriteLine("\nPredicted y = " +
predY.ToString("F4"));
Console.WriteLine("\nEnd demo ");
Console.ReadLine();
} // Main()
// ------------------------------------------------------
// helpers for Main(): MatLoad(), MatToVec(), VecShow()
// ------------------------------------------------------
static double[][] MatLoad(string fn, int[] usecols,
char sep, string comment)
{
List"lt"double[]"gt" result = new List"lt"double[]"gt"();
string line = "";
FileStream ifs = new FileStream(fn, FileMode.Open);
StreamReader sr = new StreamReader(ifs);
while ((line = sr.ReadLine()) != null)
{
if (line.StartsWith(comment) == true)
continue;
string[] tokens = line.Split(sep);
List"lt"double"gt" lst = new List"lt"double"gt"();
for (int j = 0; j "lt" usecols.Length; ++j)
lst.Add(double.Parse(tokens[usecols[j]]));
double[] row = lst.ToArray();
result.Add(row);
}
sr.Close(); ifs.Close();
return result.ToArray();
}
static double[] MatToVec(double[][] mat)
{
int nRows = mat.Length;
int nCols = mat[0].Length;
double[] result = new double[nRows * nCols];
int k = 0;
for (int i = 0; i "lt" nRows; ++i)
for (int j = 0; j "lt" nCols; ++j)
result[k++] = mat[i][j];
return result;
}
static void VecShow(double[] vec, int dec, int wid)
{
for (int i = 0; i "lt" vec.Length; ++i)
Console.Write(vec[i].ToString("F" + dec).
PadLeft(wid));
Console.WriteLine("");
}
} // class Program
// ========================================================
public class LinearRegressor
{
public double[] weights;
public double bias;
private Random rnd;
// ------------------------------------------------------
public LinearRegressor(int seed = 0) // ctor
{
this.weights = new double[0];
this.bias = 0;
this.rnd = new Random(seed); // not used this version
}
// ------------------------------------------------------
public double Predict(double[] x)
{
double result = 0.0;
for (int j = 0; j "lt" x.Length; ++j)
result += x[j] * this.weights[j];
result += this.bias;
return result;
}
// ------------------------------------------------------
public void TrainPinv(double[][] trainX, double[] trainY)
{
int dim = trainX[0].Length;
this.weights = new double[dim]; // w = pinv(dX) * y
// 1. make design matrix
int nRows = trainX.Length;
int nCols = trainX[0].Length;
double[][] X = new double[nRows][];
for (int i = 0; i "lt" nRows; ++i)
X[i] = new double[nCols + 1];
for (int i = 0; i "lt" nRows; ++i)
{
X[i][0] = 1.0;
for (int j = 1; j "lt" nCols + 1; ++j)
X[i][j] = trainX[i][j - 1];
}
// 2. compute pinv of design matrix
// a. perform QR decomp (modified Gram-Schmidt)
int m = X.Length; int n = X[0].Length;
if (m "lt" n)
throw new Exception("m must be gte n ");
double[][] Q = new double[m][]; // working Q mxn
for (int i = 0; i "lt" m; ++i)
Q[i] = new double[n];
double[][] R = new double[n][]; // working R nxn
for (int i = 0; i "lt" n; ++i)
R[i] = new double[n];
for (int k = 0; k "lt" n; ++k) // main loop each col
{
double[] v = new double[m];
for (int i = 0; i "lt" m; ++i) // col k
v[i] = X[i][k];
for (int j = 0; j "lt" k; ++j) // inner loop
{
double[] colj = new double[Q.Length];
for (int i = 0; i "lt" colj.Length; ++i)
colj[i] = Q[i][j];
double vecdot = 0.0;
for (int i = 0; i "lt" colj.Length; ++i)
vecdot += colj[i] * v[i];
R[j][k] = vecdot;
// v = v - (R[j, k] * Q[:, j])
for (int i = 0; i "lt" v.Length; ++i)
v[i] = v[i] - (R[j][k] * Q[i][j]);
} // j
double normv = 0.0;
for (int i = 0; i "lt" v.Length; ++i)
normv += v[i] * v[i];
normv = Math.Sqrt(normv);
R[k][k] = normv;
// Q[:, k] = v / R[k, k]
for (int i = 0; i "lt" Q.Length; ++i)
Q[i][k] = v[i] / (R[k][k] + 1.0e-12);
} // k
// b. compute Inv R (is upper triangular)
double[][] Rinv = new double[n][];
for (int i = 0; i "lt" n; ++i)
Rinv[i] = new double[n];
for (int i = 0; i "lt" n; ++i)
Rinv[i][i] = 1.0; // Identity
for (int k = 0; k "lt" n; ++k)
{
for (int j = 0; j "lt" n; ++j)
{
for (int i = 0; i "lt" k; ++i)
{
Rinv[j][k] -= Rinv[j][i] * R[i][k];
}
Rinv[j][k] /= (R[k][k] + 1.0e-12); // avoid 0
}
}
// c. compute inv Q == transpose Q
int nr = Q.Length; int nc = Q[0].Length;
double[][] Qinv = new double[nc][]; // note
for (int i = 0; i "lt" nc; ++i)
Qinv[i] = new double[nr];
for (int i = 0; i "lt" nr; ++i)
for (int j = 0; j "lt" nc; ++j)
Qinv[j][i] = Q[i][j]; // note
// d. result = Rinv * Qinv
int aRows = Rinv.Length; int aCols = Rinv[0].Length;
int bRows = Qinv.Length; int bCols = Qinv[0].Length;
if (aCols != bRows)
throw new Exception("Non-conformable matrices");
double[][] Xpinv = new double[aRows][];
for (int i = 0; i "lt" aRows; ++i)
Xpinv[i] = new double[bCols];
for (int i = 0; i "lt" aRows; ++i) // each row of A
for (int j = 0; j "lt" bCols; ++j) // each col of B
for (int k = 0; k "lt" aCols; ++k)
Xpinv[i][j] += Rinv[i][k] * Qinv[k][j];
// 3. compute Xpinv * trainY
double[] biasAndWts = new double[Xpinv.Length];
for (int i = 0; i "lt" Xpinv.Length; ++i)
for (int k = 0; k "lt" Xpinv[0].Length; ++k)
biasAndWts[i] += Xpinv[i][k] * trainY[k];
// 4. extract bias and weights
this.bias = biasAndWts[0];
for (int i = 1; i "lt" biasAndWts.Length; ++i)
this.weights[i - 1] = biasAndWts[i];
return;
}
// ------------------------------------------------------
public double Accuracy(double[][] dataX, double[] dataY,
double pctClose)
{
int numCorrect = 0; int numWrong = 0;
for (int i = 0; i "lt" dataX.Length; ++i)
{
double actualY = dataY[i];
double predY = this.Predict(dataX[i]);
if (Math.Abs(predY - actualY) "lt"
Math.Abs(pctClose * actualY))
++numCorrect;
else
++numWrong;
}
return (numCorrect * 1.0) / (numWrong + numCorrect);
}
// ------------------------------------------------------
public double MSE(double[][] dataX, double[] dataY)
{
int n = dataX.Length;
double sum = 0.0;
for (int i = 0; i "lt" n; ++i)
{
double actualY = dataY[i];
double predY = this.Predict(dataX[i]);
sum += (actualY - predY) * (actualY - predY);
}
return sum / n;
}
} // class LinearRegressor
} // ns
Training data:
# synthetic_train_200.txt # -0.1660, 0.4406, -0.9998, -0.3953, -0.7065, 0.4840 0.0776, -0.1616, 0.3704, -0.5911, 0.7562, 0.1568 -0.9452, 0.3409, -0.1654, 0.1174, -0.7192, 0.8054 0.9365, -0.3732, 0.3846, 0.7528, 0.7892, 0.1345 -0.8299, -0.9219, -0.6603, 0.7563, -0.8033, 0.7955 0.0663, 0.3838, -0.3690, 0.3730, 0.6693, 0.3206 -0.9634, 0.5003, 0.9777, 0.4963, -0.4391, 0.7377 -0.1042, 0.8172, -0.4128, -0.4244, -0.7399, 0.4801 -0.9613, 0.3577, -0.5767, -0.4689, -0.0169, 0.6861 -0.7065, 0.1786, 0.3995, -0.7953, -0.1719, 0.5569 0.3888, -0.1716, -0.9001, 0.0718, 0.3276, 0.2500 0.1731, 0.8068, -0.7251, -0.7214, 0.6148, 0.3297 -0.2046, -0.6693, 0.8550, -0.3045, 0.5016, 0.2129 0.2473, 0.5019, -0.3022, -0.4601, 0.7918, 0.2613 -0.1438, 0.9297, 0.3269, 0.2434, -0.7705, 0.5171 0.1568, -0.1837, -0.5259, 0.8068, 0.1474, 0.3307 -0.9943, 0.2343, -0.3467, 0.0541, 0.7719, 0.5581 0.2467, -0.9684, 0.8589, 0.3818, 0.9946, 0.1092 -0.6553, -0.7257, 0.8652, 0.3936, -0.8680, 0.7018 0.8460, 0.4230, -0.7515, -0.9602, -0.9476, 0.1996 -0.9434, -0.5076, 0.7201, 0.0777, 0.1056, 0.5664 0.9392, 0.1221, -0.9627, 0.6013, -0.5341, 0.1533 0.6142, -0.2243, 0.7271, 0.4942, 0.1125, 0.1661 0.4260, 0.1194, -0.9749, -0.8561, 0.9346, 0.2230 0.1362, -0.5934, -0.4953, 0.4877, -0.6091, 0.3810 0.6937, -0.5203, -0.0125, 0.2399, 0.6580, 0.1460 -0.6864, -0.9628, -0.8600, -0.0273, 0.2127, 0.5387 0.9772, 0.1595, -0.2397, 0.1019, 0.4907, 0.1611 0.3385, -0.4702, -0.8673, -0.2598, 0.2594, 0.2270 -0.8669, -0.4794, 0.6095, -0.6131, 0.2789, 0.4700 0.0493, 0.8496, -0.4734, -0.8681, 0.4701, 0.3516 0.8639, -0.9721, -0.5313, 0.2336, 0.8980, 0.1412 0.9004, 0.1133, 0.8312, 0.2831, -0.2200, 0.1782 0.0991, 0.8524, 0.8375, -0.2102, 0.9265, 0.2150 -0.6521, -0.7473, -0.7298, 0.0113, -0.9570, 0.7422 0.6190, -0.3105, 0.8802, 0.1640, 0.7577, 0.1056 0.6895, 0.8108, -0.0802, 0.0927, 0.5972, 0.2214 0.1982, -0.9689, 0.1870, -0.1326, 0.6147, 0.1310 -0.3695, 0.7858, 0.1557, -0.6320, 0.5759, 0.3773 -0.1596, 0.3581, 0.8372, -0.9992, 0.9535, 0.2071 -0.2468, 0.9476, 0.2094, 0.6577, 0.1494, 0.4132 0.1737, 0.5000, 0.7166, 0.5102, 0.3961, 0.2611 0.7290, -0.3546, 0.3416, -0.0983, -0.2358, 0.1332 -0.3652, 0.2438, -0.1395, 0.9476, 0.3556, 0.4170 -0.6029, -0.1466, -0.3133, 0.5953, 0.7600, 0.4334 -0.4596, -0.4953, 0.7098, 0.0554, 0.6043, 0.2775 0.1450, 0.4663, 0.0380, 0.5418, 0.1377, 0.2931 -0.8636, -0.2442, -0.8407, 0.9656, -0.6368, 0.7429 0.6237, 0.7499, 0.3768, 0.1390, -0.6781, 0.2185 -0.5499, 0.1850, -0.3755, 0.8326, 0.8193, 0.4399 -0.4858, -0.7782, -0.6141, -0.0008, 0.4572, 0.4197 0.7033, -0.1683, 0.2334, -0.5327, -0.7961, 0.1776 0.0317, -0.0457, -0.6947, 0.2436, 0.0880, 0.3345 0.5031, -0.5559, 0.0387, 0.5706, -0.9553, 0.3107 -0.3513, 0.7458, 0.6894, 0.0769, 0.7332, 0.3170 0.2205, 0.5992, -0.9309, 0.5405, 0.4635, 0.3532 -0.4806, -0.4859, 0.2646, -0.3094, 0.5932, 0.3202 0.9809, -0.3995, -0.7140, 0.8026, 0.0831, 0.1600 0.9495, 0.2732, 0.9878, 0.0921, 0.0529, 0.1289 -0.9476, -0.6792, 0.4913, -0.9392, -0.2669, 0.5966 0.7247, 0.3854, 0.3819, -0.6227, -0.1162, 0.1550 -0.5922, -0.5045, -0.4757, 0.5003, -0.0860, 0.5863 -0.8861, 0.0170, -0.5761, 0.5972, -0.4053, 0.7301 0.6877, -0.2380, 0.4997, 0.0223, 0.0819, 0.1404 0.9189, 0.6079, -0.9354, 0.4188, -0.0700, 0.1907 -0.1428, -0.7820, 0.2676, 0.6059, 0.3936, 0.2790 0.5324, -0.3151, 0.6917, -0.1425, 0.6480, 0.1071 -0.8432, -0.9633, -0.8666, -0.0828, -0.7733, 0.7784 -0.9444, 0.5097, -0.2103, 0.4939, -0.0952, 0.6787 -0.0520, 0.6063, -0.1952, 0.8094, -0.9259, 0.4836 0.5477, -0.7487, 0.2370, -0.9793, 0.0773, 0.1241 0.2450, 0.8116, 0.9799, 0.4222, 0.4636, 0.2355 0.8186, -0.1983, -0.5003, -0.6531, -0.7611, 0.1511 -0.4714, 0.6382, -0.3788, 0.9648, -0.4667, 0.5950 0.0673, -0.3711, 0.8215, -0.2669, -0.1328, 0.2677 -0.9381, 0.4338, 0.7820, -0.9454, 0.0441, 0.5518 -0.3480, 0.7190, 0.1170, 0.3805, -0.0943, 0.4724 -0.9813, 0.1535, -0.3771, 0.0345, 0.8328, 0.5438 -0.1471, -0.5052, -0.2574, 0.8637, 0.8737, 0.3042 -0.5454, -0.3712, -0.6505, 0.2142, -0.1728, 0.5783 0.6327, -0.6297, 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0.2215 -0.0242, 0.0513, -0.9430, 0.2885, -0.2987, 0.3947 -0.5416, -0.1322, -0.2351, -0.0604, 0.9590, 0.3683 0.1055, 0.7783, -0.2901, -0.5090, 0.8220, 0.2984 -0.9129, 0.9015, 0.1128, -0.2473, 0.9901, 0.4776 -0.9378, 0.1424, -0.6391, 0.2619, 0.9618, 0.5368 0.7498, -0.0963, 0.4169, 0.5549, -0.0103, 0.1614 -0.2612, -0.7156, 0.4538, -0.0460, -0.1022, 0.3717 0.7720, 0.0552, -0.1818, -0.4622, -0.8560, 0.1685 -0.4177, 0.0070, 0.9319, -0.7812, 0.3461, 0.3052 -0.0001, 0.5542, -0.7128, -0.8336, -0.2016, 0.3803 0.5356, -0.4194, -0.5662, -0.9666, -0.2027, 0.1776 -0.2378, 0.3187, -0.8582, -0.6948, -0.9668, 0.5474 -0.1947, -0.3579, 0.1158, 0.9869, 0.6690, 0.2992 0.3992, 0.8365, -0.9205, -0.8593, -0.0520, 0.3154 -0.0209, 0.0793, 0.7905, -0.1067, 0.7541, 0.1864 -0.4928, -0.4524, -0.3433, 0.0951, -0.5597, 0.6261 -0.8118, 0.7404, -0.5263, -0.2280, 0.1431, 0.6349 0.0516, -0.8480, 0.7483, 0.9023, 0.6250, 0.1959 -0.3212, 0.1093, 0.9488, -0.3766, 0.3376, 0.2735 -0.3481, 0.5490, -0.3484, 0.7797, 0.5034, 0.4379 -0.5785, -0.9170, -0.3563, -0.9258, 0.3877, 0.4121 0.3407, -0.1391, 0.5356, 0.0720, -0.9203, 0.3458 -0.3287, -0.8954, 0.2102, 0.0241, 0.2349, 0.3247 -0.1353, 0.6954, -0.0919, -0.9692, 0.7461, 0.3338 0.9036, -0.8982, -0.5299, -0.8733, -0.1567, 0.1187 0.7277, -0.8368, -0.0538, -0.7489, 0.5458, 0.0830 0.9049, 0.8878, 0.2279, 0.9470, -0.3103, 0.2194 0.7957, -0.1308, -0.5284, 0.8817, 0.3684, 0.2172 0.4647, -0.4931, 0.2010, 0.6292, -0.8918, 0.3371 -0.7390, 0.6849, 0.2367, 0.0626, -0.5034, 0.7039 -0.1567, -0.8711, 0.7940, -0.5932, 0.6525, 0.1710 0.7635, -0.0265, 0.1969, 0.0545, 0.2496, 0.1445 0.7675, 0.1354, -0.7698, -0.5460, 0.1920, 0.1728 -0.5211, -0.7372, -0.6763, 0.6897, 0.2044, 0.5217 0.1913, 0.1980, 0.2314, -0.8816, 0.5006, 0.1998 0.8964, 0.0694, -0.6149, 0.5059, -0.9854, 0.1825 0.1767, 0.7104, 0.2093, 0.6452, 0.7590, 0.2832 -0.3580, -0.7541, 0.4426, -0.1193, -0.7465, 0.5657 -0.5996, 0.5766, -0.9758, -0.3933, -0.9572, 0.6800 0.9950, 0.1641, -0.4132, 0.8579, 0.0142, 0.2003 -0.4717, -0.3894, -0.2567, -0.5111, 0.1691, 0.4266 0.3917, -0.8561, 0.9422, 0.5061, 0.6123, 0.1212 -0.0366, -0.1087, 0.3449, -0.1025, 0.4086, 0.2475 0.3633, 0.3943, 0.2372, -0.6980, 0.5216, 0.1925 -0.5325, -0.6466, -0.2178, -0.3589, 0.6310, 0.3568 0.2271, 0.5200, -0.1447, -0.8011, -0.7699, 0.3128 0.6415, 0.1993, 0.3777, -0.0178, -0.8237, 0.2181 -0.5298, -0.0768, -0.6028, -0.9490, 0.4588, 0.4356 0.6870, -0.1431, 0.7294, 0.3141, 0.1621, 0.1632 -0.5985, 0.0591, 0.7889, -0.3900, 0.7419, 0.2945 0.3661, 0.7984, -0.8486, 0.7572, -0.6183, 0.3449 0.6995, 0.3342, -0.3113, -0.6972, 0.2707, 0.1712 0.2565, 0.9126, 0.1798, -0.6043, -0.1413, 0.2893 -0.3265, 0.9839, -0.2395, 0.9854, 0.0376, 0.4770 0.2690, -0.1722, 0.9818, 0.8599, -0.7015, 0.3954 -0.2102, -0.0768, 0.1219, 0.5607, -0.0256, 0.3949 0.8216, -0.9555, 0.6422, -0.6231, 0.3715, 0.0801 -0.2896, 0.9484, -0.7545, -0.6249, 0.7789, 0.4370 -0.9985, -0.5448, -0.7092, -0.5931, 0.7926, 0.5402
Test data:
# synthetic_test_40.txt # 0.7462, 0.4006, -0.0590, 0.6543, -0.0083, 0.1935 0.8495, -0.2260, -0.0142, -0.4911, 0.7699, 0.1078 -0.2335, -0.4049, 0.4352, -0.6183, -0.7636, 0.5088 0.1810, -0.5142, 0.2465, 0.2767, -0.3449, 0.3136 -0.8650, 0.7611, -0.0801, 0.5277, -0.4922, 0.7140 -0.2358, -0.7466, -0.5115, -0.8413, -0.3943, 0.4533 0.4834, 0.2300, 0.3448, -0.9832, 0.3568, 0.1360 -0.6502, -0.6300, 0.6885, 0.9652, 0.8275, 0.3046 -0.3053, 0.5604, 0.0929, 0.6329, -0.0325, 0.4756 -0.7995, 0.0740, -0.2680, 0.2086, 0.9176, 0.4565 -0.2144, -0.2141, 0.5813, 0.2902, -0.2122, 0.4119 -0.7278, -0.0987, -0.3312, -0.5641, 0.8515, 0.4438 0.3793, 0.1976, 0.4933, 0.0839, 0.4011, 0.1905 -0.8568, 0.9573, -0.5272, 0.3212, -0.8207, 0.7415 -0.5785, 0.0056, -0.7901, -0.2223, 0.0760, 0.5551 0.0735, -0.2188, 0.3925, 0.3570, 0.3746, 0.2191 0.1230, -0.2838, 0.2262, 0.8715, 0.1938, 0.2878 0.4792, -0.9248, 0.5295, 0.0366, -0.9894, 0.3149 -0.4456, 0.0697, 0.5359, -0.8938, 0.0981, 0.3879 0.8629, -0.8505, -0.4464, 0.8385, 0.5300, 0.1769 0.1995, 0.6659, 0.7921, 0.9454, 0.9970, 0.2330 -0.0249, -0.3066, -0.2927, -0.4923, 0.8220, 0.2437 0.4513, -0.9481, -0.0770, -0.4374, -0.9421, 0.2879 -0.3405, 0.5931, -0.3507, -0.3842, 0.8562, 0.3987 0.9538, 0.0471, 0.9039, 0.7760, 0.0361, 0.1706 -0.0887, 0.2104, 0.9808, 0.5478, -0.3314, 0.4128 -0.8220, -0.6302, 0.0537, -0.1658, 0.6013, 0.4306 -0.4123, -0.2880, 0.9074, -0.0461, -0.4435, 0.5144 0.0060, 0.2867, -0.7775, 0.5161, 0.7039, 0.3599 -0.7968, -0.5484, 0.9426, -0.4308, 0.8148, 0.2979 0.7811, 0.8450, -0.6877, 0.7594, 0.2640, 0.2362 -0.6802, -0.1113, -0.8325, -0.6694, -0.6056, 0.6544 0.3821, 0.1476, 0.7466, -0.5107, 0.2592, 0.1648 0.7265, 0.9683, -0.9803, -0.4943, -0.5523, 0.2454 -0.9049, -0.9797, -0.0196, -0.9090, -0.4433, 0.6447 -0.4607, 0.1811, -0.2389, 0.4050, -0.0078, 0.5229 0.2664, -0.2932, -0.4259, -0.7336, 0.8742, 0.1834 -0.4507, 0.1029, -0.6294, -0.1158, -0.6294, 0.6081 0.8948, -0.0124, 0.9278, 0.2899, -0.0314, 0.1534 -0.1323, -0.8813, -0.0146, -0.0697, 0.6135, 0.2386

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